[dfs] add poll/select

1. Add poll/select APIs;
2. Add wait queue implementation;
3. Remove DFS_STATUS_* code and use errno;
4. Add pipe API;
5. Use a standalone fops in DFS;

29 files changed, 1793 insertions, 1546 deletions

diff --git a/components/dfs/KConfig b/components/dfs/KConfig
index 7175b5f980..5be74c7874 100644
--- a/components/dfs/KConfig
+++ b/components/dfs/KConfig
@@ -59,12 +59,13 @@ if RT_USING_DFS
         
         config RT_DFS_ELM_MAX_LFN
             int "Maximal size of file name length"
-            default 256
-        
+            range 12 255
+            default 255
+
         config RT_DFS_ELM_DRIVES
             int "Number of volumes (logical drives) to be used."
             default 2
-        
+
         config RT_DFS_ELM_MAX_SECTOR_SIZE
             int "Maximum sector size to be handled."
             default 512
@@ -86,12 +87,14 @@ if RT_USING_DFS
     
     config RT_USING_DFS_NET
         bool "Enable BSD socket operated by file system API"
+        depends on RT_USING_LWIP
         default n
         help
             Let BSD socket operated by file system API, such as read/write and involveed in select/poll POSIX APIs.
 
     config RT_USING_DFS_NFS
         bool "Using NFS v3 client file system"
+        depends on RT_USING_LWIP
         default n
 
     if RT_USING_DFS_NFS
diff --git a/components/dfs/SConscript b/components/dfs/SConscript
index e13ed292dc..5c7c8bf6a1 100644
--- a/components/dfs/SConscript
+++ b/components/dfs/SConscript
@@ -1,16 +1,24 @@
 from building import *
 
 # The set of source files associated with this SConscript file.
-src = Glob('src/*.c')
+src = Split('''
+src/dfs.c
+src/dfs_file.c
+src/dfs_fs.c
+src/dfs_posix.c
+''')
 cwd = GetCurrentDir()
 CPPPATH = [cwd + "/include"]
 
+if GetDepend('RT_USING_DFS_NET'):
+    src += ['src/poll.c', 'src/select.c']
+
 group = DefineGroup('Filesystem', src, depend = ['RT_USING_DFS'], CPPPATH = CPPPATH)
 
 if GetDepend('RT_USING_DFS'):
     # search in the file system implementation
     list = os.listdir(cwd)
-    
+
     for item in list:
         if os.path.isfile(os.path.join(cwd, item, 'SConscript')):
             group = group + SConscript(os.path.join(item, 'SConscript'))
diff --git a/components/dfs/filesystems/devfs/console.c b/components/dfs/filesystems/devfs/console.c
deleted file mode 100644
index 8c782fe6a2..0000000000
--- a/components/dfs/filesystems/devfs/console.c
+++ /dev/null
@@ -1,108 +0,0 @@
-/*
- * File      : console.c
- * This file is part of Device File System in RT-Thread RTOS
- * COPYRIGHT (C) 2004-2011, RT-Thread Development Team
- *
- *  This program is free software; you can redistribute it and/or modify
- *  it under the terms of the GNU General Public License as published by
- *  the Free Software Foundation; either version 2 of the License, or
- *  (at your option) any later version.
- *
- *  This program is distributed in the hope that it will be useful,
- *  but WITHOUT ANY WARRANTY; without even the implied warranty of
- *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- *  GNU General Public License for more details.
- *
- *  You should have received a copy of the GNU General Public License along
- *  with this program; if not, write to the Free Software Foundation, Inc.,
- *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
- *
- * Change Logs:
- * Date           Author       Notes
- * 2015.03.27     Bernard      Add author information.
- */
-
-#include <rtthread.h>
-
-struct console_device
-{
-	struct rt_device parent;
-
-	rt_device_t device; /* the actual device */
-};
-struct console_device _console;
-
-/* common device interface */
-static rt_err_t console_init(rt_device_t dev)
-{
-	return RT_EOK;
-}
-
-static rt_err_t console_open(rt_device_t dev, rt_uint16_t oflag)
-{
-	return RT_EOK;
-}
-
-static rt_err_t console_close(rt_device_t dev)
-{
-	return RT_EOK;
-}
-
-static rt_size_t console_read(rt_device_t dev, rt_off_t pos, void* buffer, rt_size_t size)
-{
-	struct console_device* device;
-
-	device = (struct console_device*)dev;
-	RT_ASSERT(device != RT_NULL);
-
-	return rt_device_read(device->device, pos, buffer, size);
-}
-
-static rt_size_t console_write(rt_device_t dev, rt_off_t pos, const void* buffer, rt_size_t size)
-{
-	struct console_device* device;
-
-	device = (struct console_device*)dev;
-	RT_ASSERT(device != RT_NULL);
-
-	return rt_device_write(device->device, pos, buffer, size);
-}
-
-static rt_err_t console_control(rt_device_t dev, rt_uint8_t cmd, void *args)
-{
-	return rt_device_control(_console.device, cmd, args);
-}
-
-void rt_console_init(const char* device_name)
-{
-	rt_device_t device;
-	/* register to device framework */
-
-	device = rt_device_find("console");
-	if (device) return; /* not register a same name device */
-
-	device = rt_device_find(device_name);
-	if (device != RT_NULL)
-	{
-		struct console_device* console;
-		/* get console device */
-		console = &_console;
-		rt_memset(console, 0, sizeof(_console));
-
-		/* device initialization */
-		console->parent.type = RT_Device_Class_Char;
-		/* set device interface */
-		console->parent.init 	= console_init;
-		console->parent.open 	= console_open;
-		console->parent.close   = console_close;
-		console->parent.read 	= console_read;
-		console->parent.write   = console_write;
-		console->parent.control	= console_control;
-		console->parent.user_data = RT_NULL;
-
-		console->device = device;
-
-		rt_device_register(&console->parent, "console", RT_DEVICE_FLAG_RDWR);
-	}
-}
-
diff --git a/components/dfs/filesystems/devfs/devfs.c b/components/dfs/filesystems/devfs/devfs.c
index fcbb738572..e61da02179 100644
--- a/components/dfs/filesystems/devfs/devfs.c
+++ b/components/dfs/filesystems/devfs/devfs.c
@@ -22,8 +22,11 @@
  */
 
 #include <rtthread.h>
+#include <rtdevice.h>
+
 #include <dfs.h>
 #include <dfs_fs.h>
+#include <dfs_file.h>
 
 #include "devfs.h"
 
@@ -36,7 +39,7 @@ struct device_dirent
 
 int dfs_device_fs_mount(struct dfs_filesystem *fs, unsigned long rwflag, const void *data)
 {
-    return DFS_STATUS_OK;
+    return RT_EOK;
 }
 
 int dfs_device_fs_ioctl(struct dfs_fd *file, int cmd, void *args)
@@ -53,12 +56,12 @@ int dfs_device_fs_ioctl(struct dfs_fd *file, int cmd, void *args)
     /* close device handler */
     result = rt_device_control(dev_id, cmd, args);
     if (result == RT_EOK)
-        return DFS_STATUS_OK;
+        return RT_EOK;
 
-    return -DFS_STATUS_EIO;
+    return result;
 }
 
-int dfs_device_fs_read(struct dfs_fd *file, void *buf, rt_size_t count)
+int dfs_device_fs_read(struct dfs_fd *file, void *buf, size_t count)
 {
     int result;
     rt_device_t dev_id;
@@ -76,7 +79,7 @@ int dfs_device_fs_read(struct dfs_fd *file, void *buf, rt_size_t count)
     return result;
 }
 
-int dfs_device_fs_write(struct dfs_fd *file, const void *buf, rt_size_t count)
+int dfs_device_fs_write(struct dfs_fd *file, const void *buf, size_t count)
 {
     int result;
     rt_device_t dev_id;
@@ -110,7 +113,7 @@ int dfs_device_fs_close(struct dfs_fd *file)
         
         /* release dirent */
         rt_free(root_dirent);
-        return DFS_STATUS_OK;
+        return RT_EOK;
     }
 
     /* get device handler */
@@ -123,10 +126,10 @@ int dfs_device_fs_close(struct dfs_fd *file)
     {
         file->data = RT_NULL;
 
-        return DFS_STATUS_OK;
+        return RT_EOK;
     }
 
-    return -DFS_STATUS_EIO;
+    return -EIO;
 }
 
 int dfs_device_fs_open(struct dfs_fd *file)
@@ -134,12 +137,12 @@ int dfs_device_fs_open(struct dfs_fd *file)
     rt_err_t result;
     rt_device_t device;
 
-    if (file->flags & DFS_O_CREAT)
-        return -DFS_STATUS_EINVAL;
+    if (file->flags & O_CREAT)
+        return -EINVAL;
 
     /* open root directory */
     if ((file->path[0] == '/') && (file->path[1] == '\0') &&
-        (file->flags & DFS_O_DIRECTORY))
+        (file->flags & O_DIRECTORY))
     {
         struct rt_object *object;
         struct rt_list_node *node;
@@ -180,23 +183,42 @@ int dfs_device_fs_open(struct dfs_fd *file)
         /* set data */
         file->data = root_dirent;
         
-        return DFS_STATUS_OK;
+        return RT_EOK;
     }
 
     device = rt_device_find(&file->path[1]);
     if (device == RT_NULL)
-        return -DFS_STATUS_ENODEV;
+        return -ENODEV;
 
-    /* to open device */
-    result = rt_device_open(device, RT_DEVICE_OFLAG_RDWR);
-    if (result == RT_EOK || result == -RT_ENOSYS)
+    if (device->fops)
     {
-        file->data = device;
-        return DFS_STATUS_OK;
+        /* use device fops */
+        file->fops = device->fops;
+        file->data = (void*)device;
+
+        /* use fops */
+        if (file->fops->open)
+        {
+            result = file->fops->open(file);
+            if (result == RT_EOK || result == -RT_ENOSYS)
+            {
+                return 0;
+            }
+        }
+    }
+    else
+    {
+        result = rt_device_open(device, RT_DEVICE_OFLAG_RDWR);
+        if (result == RT_EOK || result == -RT_ENOSYS)
+        {
+            file->data = device;
+            return RT_EOK;
+        }
     }
 
+    file->data = RT_NULL;
     /* open device failed. */
-    return -DFS_STATUS_EIO;
+    return -EIO;
 }
 
 int dfs_device_fs_stat(struct dfs_filesystem *fs, const char *path, struct stat *st)
@@ -206,15 +228,15 @@ int dfs_device_fs_stat(struct dfs_filesystem *fs, const char *path, struct stat
     {
         st->st_dev = 0;
 
-        st->st_mode = DFS_S_IFREG | DFS_S_IRUSR | DFS_S_IRGRP | DFS_S_IROTH |
-            DFS_S_IWUSR | DFS_S_IWGRP | DFS_S_IWOTH;
-        st->st_mode &= ~DFS_S_IFREG;
-        st->st_mode |= DFS_S_IFDIR | DFS_S_IXUSR | DFS_S_IXGRP | DFS_S_IXOTH;
+        st->st_mode = S_IFREG | S_IRUSR | S_IRGRP | S_IROTH |
+            S_IWUSR | S_IWGRP | S_IWOTH;
+        st->st_mode &= ~S_IFREG;
+        st->st_mode |= S_IFDIR | S_IXUSR | S_IXGRP | S_IXOTH;
 
         st->st_size  = 0;
         st->st_mtime = 0;
 
-        return DFS_STATUS_OK;
+        return RT_EOK;
     }
     else
     {
@@ -225,27 +247,29 @@ int dfs_device_fs_stat(struct dfs_filesystem *fs, const char *path, struct stat
         {
             st->st_dev = 0;
 
-            st->st_mode = DFS_S_IRUSR | DFS_S_IRGRP | DFS_S_IROTH |
-                DFS_S_IWUSR | DFS_S_IWGRP | DFS_S_IWOTH;
+            st->st_mode = S_IRUSR | S_IRGRP | S_IROTH |
+                S_IWUSR | S_IWGRP | S_IWOTH;
 
             if (dev_id->type == RT_Device_Class_Char)
-                st->st_mode |= DFS_S_IFCHR;
+                st->st_mode |= S_IFCHR;
             else if (dev_id->type == RT_Device_Class_Block)
-                st->st_mode |= DFS_S_IFBLK;
+                st->st_mode |= S_IFBLK;
+            else if (dev_id->type == RT_Device_Class_Pipe)
+                st->st_mode |= S_IFIFO;
             else
-                st->st_mode |= DFS_S_IFREG;
+                st->st_mode |= S_IFREG;
 
             st->st_size  = 0;
             st->st_mtime = 0;
 
-            return DFS_STATUS_OK;
+            return RT_EOK;
         }
     }
 
-    return -DFS_STATUS_ENOENT;
+    return -ENOENT;
 }
 
-int dfs_device_fs_getdents(struct dfs_fd *file, struct dirent *dirp, rt_uint32_t count)
+int dfs_device_fs_getdents(struct dfs_fd *file, struct dirent *dirp, uint32_t count)
 {
     rt_uint32_t index;
     rt_object_t object;
@@ -258,7 +282,7 @@ int dfs_device_fs_getdents(struct dfs_fd *file, struct dirent *dirp, rt_uint32_t
     /* make integer count */
     count = (count / sizeof(struct dirent));
     if (count == 0)
-        return -DFS_STATUS_EINVAL;
+        return -EINVAL;
 
     for (index = 0; index < count && index + root_dirent->read_index < root_dirent->device_count; 
         index ++)
@@ -266,7 +290,7 @@ int dfs_device_fs_getdents(struct dfs_fd *file, struct dirent *dirp, rt_uint32_t
         object = (rt_object_t)root_dirent->devices[root_dirent->read_index + index];
 
         d = dirp + index;
-        d->d_type = DFS_DT_REG;
+        d->d_type = DT_REG;
         d->d_namlen = RT_NAME_MAX;
         d->d_reclen = (rt_uint16_t)sizeof(struct dirent);
         rt_strncpy(d->d_name, object->name, RT_NAME_MAX);
@@ -277,23 +301,37 @@ int dfs_device_fs_getdents(struct dfs_fd *file, struct dirent *dirp, rt_uint32_t
     return index * sizeof(struct dirent);
 }
 
-static const struct dfs_filesystem_operation _device_fs = 
+static int dfs_device_fs_poll(struct dfs_fd *fd, struct rt_pollreq *req)
 {
-    "devfs",
-    DFS_FS_FLAG_DEFAULT,
-    dfs_device_fs_mount,
-    RT_NULL,
-    RT_NULL,
-    RT_NULL,
+    int mask = 0;
+
+    return mask;
+}
 
+static const struct dfs_file_ops _device_fops = 
+{
     dfs_device_fs_open,
     dfs_device_fs_close,
     dfs_device_fs_ioctl,
     dfs_device_fs_read,
     dfs_device_fs_write,
+    RT_NULL,                    /* flush */
+    RT_NULL,                    /* lseek */
+    dfs_device_fs_getdents,
+    dfs_device_fs_poll,
+};
+
+static const struct dfs_filesystem_ops _device_fs = 
+{
+    "devfs",
+    DFS_FS_FLAG_DEFAULT,
+    &_device_fops,
+
+    dfs_device_fs_mount,
     RT_NULL,
     RT_NULL,
-    dfs_device_fs_getdents,
+    RT_NULL,
+
     RT_NULL,
     dfs_device_fs_stat,
     RT_NULL,
@@ -306,5 +344,3 @@ int devfs_init(void)
 
     return 0;
 }
-INIT_FS_EXPORT(devfs_init);
-
diff --git a/components/dfs/filesystems/devfs/devfs.h b/components/dfs/filesystems/devfs/devfs.h
index 97b025634e..ef320b78c8 100644
--- a/components/dfs/filesystems/devfs/devfs.h
+++ b/components/dfs/filesystems/devfs/devfs.h
@@ -27,6 +27,5 @@
 #include <rtthread.h>
 
 int devfs_init(void);
-void rt_console_init(const char* device_name);
 
 #endif
diff --git a/components/dfs/filesystems/elmfat/dfs_elm.c b/components/dfs/filesystems/elmfat/dfs_elm.c
index 1338e3252e..eb613fe6e6 100644
--- a/components/dfs/filesystems/elmfat/dfs_elm.c
+++ b/components/dfs/filesystems/elmfat/dfs_elm.c
@@ -41,13 +41,13 @@
 #define HAVE_DIR_STRUCTURE
 
 #include <dfs_fs.h>
-#include <dfs_def.h>
+#include <dfs_file.h>
 
 static rt_device_t disk[_VOLUMES] = {0};
 
 static int elm_result_to_dfs(FRESULT result)
 {
-    int status = DFS_STATUS_OK;
+    int status = RT_EOK;
 
     switch (result)
     {
@@ -57,31 +57,31 @@ static int elm_result_to_dfs(FRESULT result)
     case FR_NO_FILE:
     case FR_NO_PATH:
     case FR_NO_FILESYSTEM:
-        status = -DFS_STATUS_ENOENT;
+        status = -ENOENT;
         break;
 
     case FR_INVALID_NAME:
-        status = -DFS_STATUS_EINVAL;
+        status = -EINVAL;
         break;
 
     case FR_EXIST:
     case FR_INVALID_OBJECT:
-        status = -DFS_STATUS_EEXIST;
+        status = -EEXIST;
         break;
 
     case FR_DISK_ERR:
     case FR_NOT_READY:
     case FR_INT_ERR:
-        status = -DFS_STATUS_EIO;
+        status = -EIO;
         break;
 
     case FR_WRITE_PROTECTED:
     case FR_DENIED:
-        status = -DFS_STATUS_EROFS;
+        status = -EROFS;
         break;
 
     case FR_MKFS_ABORTED:
-        status = -DFS_STATUS_EINVAL;
+        status = -EINVAL;
         break;
 
     default:
@@ -120,7 +120,7 @@ int dfs_elm_mount(struct dfs_filesystem *fs, unsigned long rwflag, const void *d
     /* get an empty position */
     index = get_disk(RT_NULL);
     if (index == -1)
-        return -DFS_STATUS_ENOENT;
+        return -ENOENT;
     logic_nbr[0] = '0' + index;
 
     /* save device */
@@ -131,7 +131,7 @@ int dfs_elm_mount(struct dfs_filesystem *fs, unsigned long rwflag, const void *d
         if (geometry.bytes_per_sector > _MAX_SS)
         {
             rt_kprintf("The sector size of device is greater than the sector size of FAT.\n");
-            return -DFS_STATUS_EINVAL;
+            return -EINVAL;
         }
     }
 
@@ -139,7 +139,7 @@ int dfs_elm_mount(struct dfs_filesystem *fs, unsigned long rwflag, const void *d
     if (fat == RT_NULL)
     {
         disk[index] = RT_NULL;
-        return -DFS_STATUS_ENOMEM;
+        return -ENOMEM;
     }
 
     /* mount fatfs, always 0 logic driver */
@@ -156,7 +156,7 @@ int dfs_elm_mount(struct dfs_filesystem *fs, unsigned long rwflag, const void *d
             f_mount(RT_NULL, (const TCHAR*)logic_nbr, 1);
             disk[index] = RT_NULL;
             rt_free(fat);
-            return -DFS_STATUS_ENOMEM;
+            return -ENOMEM;
         }
 
         /* open the root directory to test whether the fatfs is valid */
@@ -190,7 +190,7 @@ int dfs_elm_unmount(struct dfs_filesystem *fs)
     /* find the device index and then umount it */
     index = get_disk(fs->dev_id);
     if (index == -1) /* not found */
-        return -DFS_STATUS_ENOENT;
+        return -ENOENT;
 
     result = f_mount(RT_NULL, "", (BYTE)index);
     if (result != FR_OK)
@@ -200,7 +200,7 @@ int dfs_elm_unmount(struct dfs_filesystem *fs)
     disk[index] = RT_NULL;
     rt_free(fat);
 
-    return DFS_STATUS_OK;
+    return RT_EOK;
 }
 
 int dfs_elm_mkfs(rt_device_t dev_id)
@@ -212,15 +212,17 @@ int dfs_elm_mkfs(rt_device_t dev_id)
     int flag;
     FRESULT result;
     int index;
-    char logic_nbr[2] = {'0',':'};
 
     work = rt_malloc(_MAX_SS);
     if(RT_NULL == work) {
-        return -DFS_STATUS_ENOMEM;
+        return -ENOMEM;
     }
 
     if (dev_id == RT_NULL)
-        return -DFS_STATUS_EINVAL;
+    {
+        rt_free(work); /* release memory */
+        return -EINVAL;
+    }
 
     /* if the device is already mounted, then just do mkfs to the drv,
      * while if it is not mounted yet, then find an empty drive to do mkfs
@@ -236,13 +238,17 @@ int dfs_elm_mkfs(rt_device_t dev_id)
         {
             /* no space to store an temp driver */
             rt_kprintf("sorry, there is no space to do mkfs! \n");
-            return -DFS_STATUS_ENOSPC;
+            rt_free(work); /* release memory */
+            return -ENOSPC;
         }
         else
         {
             fat = rt_malloc(sizeof(FATFS));
             if (fat == RT_NULL)
-                return -DFS_STATUS_ENOMEM;
+            {
+                rt_free(work); /* release memory */
+                return -ENOMEM;
+            }
 
             flag = FSM_STATUS_USE_TEMP_DRIVER;
 
@@ -256,26 +262,23 @@ int dfs_elm_mkfs(rt_device_t dev_id)
              * on the disk, you will get a failure. so we need f_mount here,
              * just fill the FatFS[index] in elm fatfs to make mkfs work.
              */
-            logic_nbr[0] = '0' + index;
-            f_mount(fat, logic_nbr, (BYTE)index);
+            f_mount(fat, "", (BYTE)index);
         }
     }
-    else
-        logic_nbr[0] = '0' + index;
 
     /* [IN] Logical drive number */
     /* [IN] Format options */
     /* [IN] Size of the allocation unit */
     /* [-]  Working buffer */
     /* [IN] Size of working buffer */
-    result = f_mkfs(logic_nbr, FM_ANY, 0, work, _MAX_SS);
-    rt_free(work);
+    result = f_mkfs("", FM_ANY, 0, work, _MAX_SS);
+    rt_free(work); work = RT_NULL;
 
     /* check flag status, we need clear the temp driver stored in disk[] */
     if (flag == FSM_STATUS_USE_TEMP_DRIVER)
     {
         rt_free(fat);
-        f_mount(RT_NULL, logic_nbr,(BYTE)index);
+        f_mount(RT_NULL, "",(BYTE)index);
         disk[index] = RT_NULL;
         /* close device */
         rt_device_close(dev_id);
@@ -287,7 +290,7 @@ int dfs_elm_mkfs(rt_device_t dev_id)
         return elm_result_to_dfs(result);
     }
 
-    return DFS_STATUS_OK;
+    return RT_EOK;
 }
 
 int dfs_elm_statfs(struct dfs_filesystem *fs, struct statfs *buf)
@@ -331,26 +334,30 @@ int dfs_elm_open(struct dfs_fd *file)
 
 #if (_VOLUMES > 1)
     int vol;
+    struct dfs_filesystem *fs = (struct dfs_filesystem *)file->data;
     extern int elm_get_vol(FATFS * fat);
 
+    if (fs == NULL)
+        return -ENOENT;
+
     /* add path for ELM FatFS driver support */
-    vol = elm_get_vol((FATFS *)file->fs->data);
+    vol = elm_get_vol((FATFS *)fs->data);
     if (vol < 0)
-        return -DFS_STATUS_ENOENT;
+        return -ENOENT;
     drivers_fn = rt_malloc(256);
     if (drivers_fn == RT_NULL)
-        return -DFS_STATUS_ENOMEM;
+        return -ENOMEM;
 
     rt_snprintf(drivers_fn, 256, "%d:%s", vol, file->path);
 #else
     drivers_fn = file->path;
 #endif
 
-    if (file->flags & DFS_O_DIRECTORY)
+    if (file->flags & O_DIRECTORY)
     {
         DIR *dir;
 
-        if (file->flags & DFS_O_CREAT)
+        if (file->flags & O_CREAT)
         {
             result = f_mkdir(drivers_fn);
             if (result != FR_OK)
@@ -369,7 +376,7 @@ int dfs_elm_open(struct dfs_fd *file)
 #if _VOLUMES > 1
             rt_free(drivers_fn);
 #endif
-            return -DFS_STATUS_ENOMEM;
+            return -ENOMEM;
         }
 
         result = f_opendir(dir, drivers_fn);
@@ -383,24 +390,24 @@ int dfs_elm_open(struct dfs_fd *file)
         }
 
         file->data = dir;
-        return DFS_STATUS_OK;
+        return RT_EOK;
     }
     else
     {
         mode = FA_READ;
 
-        if (file->flags & DFS_O_WRONLY)
+        if (file->flags & O_WRONLY)
             mode |= FA_WRITE;
-        if ((file->flags & DFS_O_ACCMODE) & DFS_O_RDWR)
+        if ((file->flags & O_ACCMODE) & O_RDWR)
             mode |= FA_WRITE;
         /* Opens the file, if it is existing. If not, a new file is created. */
-        if (file->flags & DFS_O_CREAT)
+        if (file->flags & O_CREAT)
             mode |= FA_OPEN_ALWAYS;
         /* Creates a new file. If the file is existing, it is truncated and overwritten. */
-        if (file->flags & DFS_O_TRUNC)
+        if (file->flags & O_TRUNC)
             mode |= FA_CREATE_ALWAYS;
         /* Creates a new file. The function fails if the file is already existing. */
-        if (file->flags & DFS_O_EXCL)
+        if (file->flags & O_EXCL)
             mode |= FA_CREATE_NEW;
 
         /* allocate a fd */
@@ -410,7 +417,7 @@ int dfs_elm_open(struct dfs_fd *file)
 #if _VOLUMES > 1
             rt_free(drivers_fn);
 #endif
-            return -DFS_STATUS_ENOMEM;
+            return -ENOMEM;
         }
 
         result = f_open(fd, drivers_fn, mode);
@@ -423,7 +430,7 @@ int dfs_elm_open(struct dfs_fd *file)
             file->size = f_size(fd);
             file->data = fd;
 
-            if (file->flags & DFS_O_APPEND)
+            if (file->flags & O_APPEND)
             {
                 /* seek to the end of file */
                 f_lseek(fd, f_size(fd));
@@ -438,7 +445,7 @@ int dfs_elm_open(struct dfs_fd *file)
         }
     }
 
-    return DFS_STATUS_OK;
+    return RT_EOK;
 }
 
 int dfs_elm_close(struct dfs_fd *file)
@@ -475,10 +482,10 @@ int dfs_elm_close(struct dfs_fd *file)
 
 int dfs_elm_ioctl(struct dfs_fd *file, int cmd, void *args)
 {
-    return -DFS_STATUS_ENOSYS;
+    return -ENOSYS;
 }
 
-int dfs_elm_read(struct dfs_fd *file, void *buf, rt_size_t len)
+int dfs_elm_read(struct dfs_fd *file, void *buf, size_t len)
 {
     FIL *fd;
     FRESULT result;
@@ -486,7 +493,7 @@ int dfs_elm_read(struct dfs_fd *file, void *buf, rt_size_t len)
 
     if (file->type == FT_DIRECTORY)
     {
-        return -DFS_STATUS_EISDIR;
+        return -EISDIR;
     }
 
     fd = (FIL *)(file->data);
@@ -501,7 +508,7 @@ int dfs_elm_read(struct dfs_fd *file, void *buf, rt_size_t len)
     return elm_result_to_dfs(result);
 }
 
-int dfs_elm_write(struct dfs_fd *file, const void *buf, rt_size_t len)
+int dfs_elm_write(struct dfs_fd *file, const void *buf, size_t len)
 {
     FIL *fd;
     FRESULT result;
@@ -509,7 +516,7 @@ int dfs_elm_write(struct dfs_fd *file, const void *buf, rt_size_t len)
 
     if (file->type == FT_DIRECTORY)
     {
-        return -DFS_STATUS_EISDIR;
+        return -EISDIR;
     }
 
     fd = (FIL *)(file->data);
@@ -576,7 +583,7 @@ int dfs_elm_lseek(struct dfs_fd *file, rt_off_t offset)
     return elm_result_to_dfs(result);
 }
 
-int dfs_elm_getdents(struct dfs_fd *file, struct dirent *dirp, rt_uint32_t count)
+int dfs_elm_getdents(struct dfs_fd *file, struct dirent *dirp, uint32_t count)
 {
     DIR *dir;
     FILINFO fno;
@@ -590,7 +597,7 @@ int dfs_elm_getdents(struct dfs_fd *file, struct dirent *dirp, rt_uint32_t count
     /* make integer count */
     count = (count / sizeof(struct dirent)) * sizeof(struct dirent);
     if (count == 0)
-        return -DFS_STATUS_EINVAL;
+        return -EINVAL;
 
     index = 0;
     while (1)
@@ -609,11 +616,11 @@ int dfs_elm_getdents(struct dfs_fd *file, struct dirent *dirp, rt_uint32_t count
         fn = fno.fname;
 #endif
 
-        d->d_type = DFS_DT_UNKNOWN;
+        d->d_type = DT_UNKNOWN;
         if (fno.fattrib & AM_DIR)
-            d->d_type = DFS_DT_DIR;
+            d->d_type = DT_DIR;
         else
-            d->d_type = DFS_DT_REG;
+            d->d_type = DT_REG;
 
         d->d_namlen = (rt_uint8_t)rt_strlen(fn);
         d->d_reclen = (rt_uint16_t)sizeof(struct dirent);
@@ -644,10 +651,10 @@ int dfs_elm_unlink(struct dfs_filesystem *fs, const char *path)
     /* add path for ELM FatFS driver support */
     vol = elm_get_vol((FATFS *)fs->data);
     if (vol < 0)
-        return -DFS_STATUS_ENOENT;
+        return -ENOENT;
     drivers_fn = rt_malloc(256);
     if (drivers_fn == RT_NULL)
-        return -DFS_STATUS_ENOMEM;
+        return -ENOMEM;
 
     rt_snprintf(drivers_fn, 256, "%d:%s", vol, path);
 #else
@@ -675,11 +682,11 @@ int dfs_elm_rename(struct dfs_filesystem *fs, const char *oldpath, const char *n
     /* add path for ELM FatFS driver support */
     vol = elm_get_vol((FATFS *)fs->data);
     if (vol < 0)
-        return -DFS_STATUS_ENOENT;
+        return -ENOENT;
 
     drivers_oldfn = rt_malloc(256);
     if (drivers_oldfn == RT_NULL)
-        return -DFS_STATUS_ENOMEM;
+        return -ENOMEM;
     drivers_newfn = newpath;
 
     rt_snprintf(drivers_oldfn, 256, "%d:%s", vol, oldpath);
@@ -710,10 +717,10 @@ int dfs_elm_stat(struct dfs_filesystem *fs, const char *path, struct stat *st)
     /* add path for ELM FatFS driver support */
     vol = elm_get_vol((FATFS *)fs->data);
     if (vol < 0)
-        return -DFS_STATUS_ENOENT;
+        return -ENOENT;
     drivers_fn = rt_malloc(256);
     if (drivers_fn == RT_NULL)
-        return -DFS_STATUS_ENOMEM;
+        return -ENOMEM;
 
     rt_snprintf(drivers_fn, 256, "%d:%s", vol, path);
 #else
@@ -730,15 +737,15 @@ int dfs_elm_stat(struct dfs_filesystem *fs, const char *path, struct stat *st)
         /* convert to dfs stat structure */
         st->st_dev = 0;
 
-        st->st_mode = DFS_S_IFREG | DFS_S_IRUSR | DFS_S_IRGRP | DFS_S_IROTH |
-                      DFS_S_IWUSR | DFS_S_IWGRP | DFS_S_IWOTH;
+        st->st_mode = S_IFREG | S_IRUSR | S_IRGRP | S_IROTH |
+                      S_IWUSR | S_IWGRP | S_IWOTH;
         if (file_info.fattrib & AM_DIR)
         {
-            st->st_mode &= ~DFS_S_IFREG;
-            st->st_mode |= DFS_S_IFDIR | DFS_S_IXUSR | DFS_S_IXGRP | DFS_S_IXOTH;
+            st->st_mode &= ~S_IFREG;
+            st->st_mode |= S_IFDIR | S_IXUSR | S_IXGRP | S_IXOTH;
         }
         if (file_info.fattrib & AM_RDO)
-            st->st_mode &= ~(DFS_S_IWUSR | DFS_S_IWGRP | DFS_S_IWOTH);
+            st->st_mode &= ~(S_IWUSR | S_IWGRP | S_IWOTH);
 
         st->st_size  = file_info.fsize;
 
@@ -777,15 +784,8 @@ int dfs_elm_stat(struct dfs_filesystem *fs, const char *path, struct stat *st)
     return elm_result_to_dfs(result);
 }
 
-static const struct dfs_filesystem_operation dfs_elm =
+static const struct dfs_file_ops dfs_elm_fops = 
 {
-    "elm",
-    DFS_FS_FLAG_DEFAULT,
-    dfs_elm_mount,
-    dfs_elm_unmount,
-    dfs_elm_mkfs,
-    dfs_elm_statfs,
-
     dfs_elm_open,
     dfs_elm_close,
     dfs_elm_ioctl,
@@ -794,6 +794,20 @@ static const struct dfs_filesystem_operation dfs_elm =
     dfs_elm_flush,
     dfs_elm_lseek,
     dfs_elm_getdents,
+    RT_NULL, /* poll interface */
+};
+
+static const struct dfs_filesystem_ops dfs_elm =
+{
+    "elm",
+    DFS_FS_FLAG_DEFAULT,
+    &dfs_elm_fops,
+
+    dfs_elm_mount,
+    dfs_elm_unmount,
+    dfs_elm_mkfs,
+    dfs_elm_statfs,
+
     dfs_elm_unlink,
     dfs_elm_stat,
     dfs_elm_rename,
diff --git a/components/dfs/include/dfs_elm.h b/components/dfs/filesystems/elmfat/dfs_elm.h
index da8a217005..da8a217005 100644
--- a/components/dfs/include/dfs_elm.h
+++ b/components/dfs/filesystems/elmfat/dfs_elm.h
diff --git a/components/dfs/filesystems/net/dfs_net.c b/components/dfs/filesystems/net/dfs_net.c
index cda8407f17..2a91434ef0 100644
--- a/components/dfs/filesystems/net/dfs_net.c
+++ b/components/dfs/filesystems/net/dfs_net.c
@@ -26,27 +26,35 @@
 #include <rtthread.h>
 #include <dfs.h>
 #include <dfs_fs.h>
+#include <dfs_file.h>
+#include <dfs_posix.h>
+
+#include <rtdevice.h>
+#include <sys/socket.h>
 
 #include "dfs_net.h"
 
 int dfs_net_getsocket(int fd)
 {
+    int sock;
     struct dfs_fd *_dfs_fd; 
-    
+
     _dfs_fd = fd_get(fd);
-    if (_dfs_fd == RT_NULL) return -1;
+    if (_dfs_fd == NULL) return -1;
 
-    if (_dfs_fd->type != FT_SOCKET) return -1;
-    
-    return (int)_dfs_fd->data;
+    if (_dfs_fd->type != FT_SOCKET) sock = -1;
+    else sock = (int)_dfs_fd->data;
+
+    fd_put(_dfs_fd); /* put this dfs fd */
+    return sock;
 }
 
-int dfs_net_ioctl(struct dfs_fd* file, int cmd, void* args)
+static int dfs_net_ioctl(struct dfs_fd* file, int cmd, void* args)
 {
-    return -DFS_STATUS_EIO;
+    return -EIO;
 }
 
-int dfs_net_read(struct dfs_fd* file, void *buf, rt_size_t count)
+static int dfs_net_read(struct dfs_fd* file, void *buf, size_t count)
 {
     int sock;
 
@@ -56,7 +64,7 @@ int dfs_net_read(struct dfs_fd* file, void *buf, rt_size_t count)
     return count;
 }
 
-int dfs_net_write(struct dfs_fd *file, const void *buf, rt_size_t count)
+static int dfs_net_write(struct dfs_fd *file, const void *buf, size_t count)
 {
     int sock;
     
@@ -66,7 +74,7 @@ int dfs_net_write(struct dfs_fd *file, const void *buf, rt_size_t count)
     return count;
 }
 
-int dfs_net_close(struct dfs_fd* file)
+static int dfs_net_close(struct dfs_fd* file)
 {
     int sock;
     int result;
@@ -74,55 +82,60 @@ int dfs_net_close(struct dfs_fd* file)
     sock = (int)file->data;
     result = lwip_close(sock);
     
-    if (result == 0) return DFS_STATUS_OK;
+    if (result == 0) return RT_EOK;
     
     return -result;
 }
 
-static const struct dfs_filesystem_operation _net_fs_ops = 
+static int dfs_net_poll(struct dfs_fd *file, struct rt_pollreq *req)
 {
-    "net",
-    DFS_FS_FLAG_DEFAULT,
-    RT_NULL,    /* mount    */
-    RT_NULL,    /* unmont   */
-    RT_NULL,    /* mkfs     */
-    RT_NULL,    /* statfs   */
+    int sfd;
+    int mask = 0;
+    struct lwip_sock *sock;
 
-    RT_NULL,    /* open     */
+    sfd = (int)file->data;
+
+    sock =  lwip_tryget_socket(sfd);
+    if (sock != NULL)
+    {
+        rt_base_t level;
+
+        rt_poll_add(&sock->wait_head, req);
+
+        level = rt_hw_interrupt_disable();
+        if (sock->rcvevent)
+        {
+            mask |= POLLIN;
+        }
+        if (sock->sendevent)
+        {
+            mask |= POLLOUT;
+        }
+        if (sock->errevent)
+        {
+            mask |= POLLERR;
+        }
+        rt_hw_interrupt_enable(level);
+    }
+
+    return mask;
+}
+
+const struct dfs_file_ops _net_fops = 
+{
+    NULL,    /* open     */
     dfs_net_close,
     dfs_net_ioctl,
     dfs_net_read,
     dfs_net_write,
-    RT_NULL,
-    RT_NULL,    /* lseek    */
-    RT_NULL,    /* getdents */
-    RT_NULL,    /* unlink   */
-    RT_NULL,    /* stat     */
-    RT_NULL,    /* rename   */
-};
-
-static struct dfs_filesystem _net_fs = 
-{
-    0,              /* dev_id */
-    RT_NULL,        /* path */
-    &_net_fs_ops,
-    RT_NULL         /* data */
+    NULL,
+    NULL,    /* lseek    */
+    NULL,    /* getdents */
+    dfs_net_poll,
 };
 
-struct dfs_filesystem* dfs_net_get_fs(void)
+const struct dfs_file_ops *dfs_net_get_fops(void)
 {
-    return &_net_fs;
+    return &_net_fops;
 }
 
-/*
-NOTE: Beause we don't need to mount lwIP file system, the filesystem_ops is not 
-registered to the system. 
-
-int dfs_net_system_init(void)
-{
-    dfs_register(&_net_fs_ops);
-    
-    return 0;
-}
-INIT_FS_EXPORT(dfs_net_system_init);
-*/
diff --git a/components/dfs/filesystems/net/dfs_net.h b/components/dfs/filesystems/net/dfs_net.h
index d98b719b89..647e6b5f3a 100644
--- a/components/dfs/filesystems/net/dfs_net.h
+++ b/components/dfs/filesystems/net/dfs_net.h
@@ -32,13 +32,12 @@ extern "C" {
 
 #include <lwip/sockets.h>
 
-struct dfs_filesystem* dfs_net_get_fs(void);
+const struct dfs_file_ops* dfs_net_get_fops(void);
 int dfs_net_getsocket(int fd);
 
-int dfs_net_system_init(void);
-
 #ifdef __cplusplus
 }
 #endif
 
 #endif
+
diff --git a/components/dfs/filesystems/net/net_select.c b/components/dfs/filesystems/net/net_select.c
deleted file mode 100644
index d19ff0ed1b..0000000000
--- a/components/dfs/filesystems/net/net_select.c
+++ /dev/null
@@ -1,123 +0,0 @@
-/*
- * File      : lwip_select.c
- * This file is part of RT-Thread RTOS
- * COPYRIGHT (C) 2015, RT-Thread Development Team
- *
- *  This program is free software; you can redistribute it and/or modify
- *  it under the terms of the GNU General Public License as published by
- *  the Free Software Foundation; either version 2 of the License, or
- *  (at your option) any later version.
- *
- *  This program is distributed in the hope that it will be useful,
- *  but WITHOUT ANY WARRANTY; without even the implied warranty of
- *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- *  GNU General Public License for more details.
- *
- *  You should have received a copy of the GNU General Public License along
- *  with this program; if not, write to the Free Software Foundation, Inc.,
- *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
- *
- * Change Logs:
- * Date           Author       Notes
- * 2015-05-05     Bernard      First version
- */
-
-#include <rtthread.h>
-#include <sys/select.h>
-
-#ifdef RT_USING_LWIP
-
-#include "dfs_net.h"
-
-int
-select(int maxfdp1, fd_set *readset, fd_set *writeset, fd_set *exceptset,
-            struct timeval *timeout)
-{
-    int index, result;
-    int sock, maxfd;
-
-    fd_set sock_readset;
-    fd_set sock_writeset;
-    fd_set sock_exceptset;
-
-    FD_ZERO(&sock_readset);
-    FD_ZERO(&sock_writeset);
-    FD_ZERO(&sock_exceptset);
-
-    maxfd = 0;
-    for (index = 0; index < maxfdp1; index ++)
-    {
-        /* convert fd to sock */
-        sock = dfs_net_getsocket(index);
-        if (sock == -1) continue;
-
-        if (sock > maxfd) maxfd = sock;
-
-        /* if FD is set, set the socket set */
-        if (readset && FD_ISSET(index, readset))
-        {
-            FD_SET(sock, &sock_readset);
-        }
-        if (writeset && FD_ISSET(index, writeset))
-        {
-            FD_SET(sock, &sock_writeset);
-        }
-        if (exceptset && FD_ISSET(index, exceptset))
-        {
-            FD_SET(sock, &sock_exceptset);
-        }
-    }
-
-    /* no socket found, return bad file descriptor */
-    if (maxfd == 0) return -EBADF;
-    maxfd += 1;
-    
-    result = lwip_select(maxfd, &sock_readset, &sock_writeset, &sock_exceptset, timeout);
-    
-    if (readset)   FD_ZERO(readset);
-    if (writeset)  FD_ZERO(writeset);
-    if (exceptset) FD_ZERO(exceptset);
-
-    if (result != -1)
-    {
-        for (index = 0; index < maxfd; index ++)
-        {
-            /* check each socket */
-            if ((FD_ISSET(index, &sock_readset))  ||
-                (FD_ISSET(index, &sock_writeset)) ||
-                (FD_ISSET(index, &sock_exceptset)))
-            {
-                int fd_index;
-                
-                /* Because we can not get the corresponding fd, we have to search it one by one */
-                for (fd_index = 0; fd_index < maxfdp1; fd_index ++)
-                {
-                    sock = dfs_lwip_getsocket(fd_index);
-                    if (sock == index) /* found it */
-                    {
-                        if (readset && FD_ISSET(index, &sock_readset))
-                        {
-                            FD_SET(sock, readset);
-                        }
-                        if (writeset && FD_ISSET(index, &sock_writeset))
-                        {
-                            FD_SET(sock, writeset);
-                        }
-                        if (exceptset && FD_ISSET(index, &sock_exceptset))
-                        {
-                            FD_SET(sock, exceptset);
-                        }
-                        
-                        /* end of search */
-                        break;
-                    }
-                }
-            }
-        }
-    }
-    
-    return result;
-}
-RTM_EXPORT(select);
-
-#endif
diff --git a/components/dfs/filesystems/net/net_sockets.c b/components/dfs/filesystems/net/net_sockets.c
index a37633e18f..0161cb0be5 100644
--- a/components/dfs/filesystems/net/net_sockets.c
+++ b/components/dfs/filesystems/net/net_sockets.c
@@ -23,13 +23,92 @@
  */
 
 #include <dfs.h>
-#include <dfs_def.h>
 #include <dfs_posix.h>
-
 #include <sys/socket.h>
 
 #include "dfs_net.h"
 
+static void event_callback(struct netconn *conn, enum netconn_evt evt, u16_t len)
+{
+    int s;
+    struct lwip_sock *sock;
+    uint32_t event = 0;
+    SYS_ARCH_DECL_PROTECT(lev);
+
+    LWIP_UNUSED_ARG(len);
+
+    /* Get socket */
+    if (conn)
+    {
+        s = conn->socket;
+        if (s < 0)
+        {
+            /* Data comes in right away after an accept, even though
+             * the server task might not have created a new socket yet.
+             * Just count down (or up) if that's the case and we
+             * will use the data later. Note that only receive events
+             * can happen before the new socket is set up. */
+            SYS_ARCH_PROTECT(lev);
+            if (conn->socket < 0)
+            {
+                if (evt == NETCONN_EVT_RCVPLUS)
+                {
+                    conn->socket--;
+                }
+                SYS_ARCH_UNPROTECT(lev);
+                return;
+            }
+            s = conn->socket;
+            SYS_ARCH_UNPROTECT(lev);
+        }
+
+        sock = lwip_tryget_socket(s);
+        if (!sock)
+        {
+            return;
+        }
+    }
+    else
+    {
+        return;
+    }
+
+    SYS_ARCH_PROTECT(lev);
+    /* Set event as required */
+    switch (evt)
+    {
+    case NETCONN_EVT_RCVPLUS:
+        sock->rcvevent++;
+        break;
+    case NETCONN_EVT_RCVMINUS:
+        sock->rcvevent--;
+        break;
+    case NETCONN_EVT_SENDPLUS:
+        sock->sendevent = 1;
+        break;
+    case NETCONN_EVT_SENDMINUS:
+        sock->sendevent = 0;
+        break;
+    case NETCONN_EVT_ERROR:
+        sock->errevent = 1;
+        break;
+    default:
+        LWIP_ASSERT("unknown event", 0);
+        break;
+    }
+
+    if (sock->lastdata || sock->rcvevent > 0) event |= POLLIN;
+    if (sock->sendevent) event |= POLLOUT;
+    if (sock->errevent)  event |= POLLERR;
+
+    SYS_ARCH_UNPROTECT(lev);
+
+    if (event)
+    {
+        rt_wqueue_wakeup(&sock->wait_head, (void*)event);
+    }
+}
+
 int accept(int s, struct sockaddr *addr, socklen_t *addrlen)
 {
     int new_client = -1;
@@ -41,15 +120,15 @@ int accept(int s, struct sockaddr *addr, socklen_t *addrlen)
         /* this is a new socket, create it in file system fd */
         int fd;
         struct dfs_fd *d;
-
+        struct lwip_sock *lwsock;
+        
         /* allocate a fd */
         fd = fd_new();
         if (fd < 0)
         {
-            rt_set_errno(-DFS_STATUS_ENOMEM);
+            rt_set_errno(-ENOMEM);
             lwip_close(sock);
 
-            rt_kprintf("no fd yet!\n");
             return -1;
         }
         d = fd_get(fd);
@@ -58,9 +137,12 @@ int accept(int s, struct sockaddr *addr, socklen_t *addrlen)
         d->type = FT_SOCKET;
         d->path = RT_NULL;
 
-        d->fs = dfs_net_get_fs();
+        d->fops = dfs_net_get_fops();
+        /* initialize wait head */
+        lwsock = lwip_tryget_socket(new_client);
+        rt_list_init(&(lwsock->wait_head));
 
-        d->flags = DFS_O_RDWR; /* set flags as read and write */
+        d->flags = O_RDWR; /* set flags as read and write */
         d->size = 0;
         d->pos  = 0;
 
@@ -93,7 +175,7 @@ int shutdown(int s, int how)
     d = fd_get(s);
     if (d == RT_NULL)
     {
-        rt_set_errno(-DFS_STATUS_EBADF);
+        rt_set_errno(-EBADF);
 
         return -1;
     }
@@ -200,12 +282,13 @@ int socket(int domain, int type, int protocol)
     int fd;
     int sock;
     struct dfs_fd *d;
+    struct lwip_sock *lwsock;
 
     /* allocate a fd */
     fd = fd_new();
     if (fd < 0)
     {
-        rt_set_errno(-DFS_STATUS_ENOMEM);
+        rt_set_errno(-ENOMEM);
 
         return -1;
     }
@@ -213,20 +296,24 @@ int socket(int domain, int type, int protocol)
 
     /* create socket in lwip and then put it to the dfs_fd */
     sock = lwip_socket(domain, type, protocol);
-    if (sock > 0)
+    if (sock >= 0)
     {
         /* this is a socket fd */
-        d->type = FT_SOCKET;
-        d->path = RT_NULL;
+        d->type  = FT_SOCKET;
+        d->path  = NULL;
 
-        d->fs = dfs_net_get_fs();
+        d->fops  = dfs_net_get_fops();
 
-        d->flags = DFS_O_RDWR; /* set flags as read and write */
-        d->size = 0;
-        d->pos  = 0;
+        d->flags = O_RDWR; /* set flags as read and write */
+        d->size  = 0;
+        d->pos   = 0;
 
         /* set socket to the data of dfs_fd */
         d->data = (void *) sock;
+
+        lwsock = lwip_tryget_socket(sock);
+        rt_list_init(&(lwsock->wait_head));
+        lwsock->conn->callback = event_callback;
     }
 
     /* release the ref-count of fd */
@@ -235,3 +322,20 @@ int socket(int domain, int type, int protocol)
     return fd;
 }
 RTM_EXPORT(socket);
+
+int closesocket(int s)
+{
+    int sock = dfs_net_getsocket(s);
+
+    return lwip_close(sock);
+}
+RTM_EXPORT(closesocket);
+
+int ioctlsocket(int s, long cmd, void *arg)
+{
+    int sock = dfs_net_getsocket(s);
+
+    return lwip_ioctl(sock, cmd, arg);
+}
+RTM_EXPORT(ioctlsocket);
+
diff --git a/components/dfs/filesystems/net/sys/select.h b/components/dfs/filesystems/net/sys/select.h
index 406913d5db..ce91583904 100644
--- a/components/dfs/filesystems/net/sys/select.h
+++ b/components/dfs/filesystems/net/sys/select.h
@@ -25,22 +25,6 @@
 #ifndef SELECT_H__
 #define SELECT_H__
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
-/* select API */
-#ifdef RT_USING_LWIP
-/* we use lwIP's structure definitions. */
-#include <lwip/sockets.h>
-
-int
-select(int maxfdp1, fd_set *readset, fd_set *writeset, fd_set *exceptset,
-            struct timeval *timeout);
-#endif
-
-#ifdef __cplusplus
-}
-#endif
+#include <dfs_select.h>
 
 #endif
diff --git a/components/dfs/filesystems/net/sys/socket.h b/components/dfs/filesystems/net/sys/socket.h
index b9608d97ed..89e0c5bfa5 100644
--- a/components/dfs/filesystems/net/sys/socket.h
+++ b/components/dfs/filesystems/net/sys/socket.h
@@ -31,7 +31,12 @@ extern "C" {
 
 #include <inttypes.h>
 #include <lwip/sockets.h>
+#include <lwip/api.h>
+#include <lwip/init.h>
 
+#include <rtdevice.h>
+
+#if LWIP_VERSION < 0x2000000
 typedef uint16_t sa_family_t;
 typedef uint16_t in_port_t;
 
@@ -40,6 +45,44 @@ struct sockaddr_storage
     sa_family_t ss_family;       /* Address family */
     char        ss_data[14];     /* 14-bytes of address data */
 };
+#endif
+
+#if LWIP_VERSION < 0x2000000
+#define SELWAIT_T int
+#else
+#ifndef SELWAIT_T
+#define SELWAIT_T u8_t
+#endif
+#endif
+
+/*
+ * Re-define lwip socket
+ *
+ * NOTE: please make sure the definitions same in lwip::net_socket.c
+ */
+struct lwip_sock {
+  /** sockets currently are built on netconns, each socket has one netconn */
+  struct netconn *conn;
+  /** data that was left from the previous read */
+  void *lastdata;
+  /** offset in the data that was left from the previous read */
+  u16_t lastoffset;
+  /** number of times data was received, set by event_callback(),
+      tested by the receive and select functions */
+  s16_t rcvevent;
+  /** number of times data was ACKed (free send buffer), set by event_callback(),
+      tested by select */
+  u16_t sendevent;
+  /** error happened for this socket, set by event_callback(), tested by select */
+  u16_t errevent;
+  /** last error that occurred on this socket */
+  int err;
+  /** counter of how many threads are waiting for this socket using select */
+  SELWAIT_T select_waiting;
+
+  rt_wqueue_t wait_head;
+};
+struct lwip_sock *lwip_tryget_socket(int s);
 
 int accept(int s, struct sockaddr *addr, socklen_t *addrlen);
 int bind(int s, const struct sockaddr *name, socklen_t namelen);
@@ -57,6 +100,8 @@ int send(int s, const void *dataptr, size_t size, int flags);
 int sendto(int s, const void *dataptr, size_t size, int flags,
     const struct sockaddr *to, socklen_t tolen);
 int socket(int domain, int type, int protocol);
+int closesocket(int s);
+int ioctlsocket(int s, long cmd, void *arg);
 
 #ifdef __cplusplus
 }
diff --git a/components/dfs/filesystems/ramfs/dfs_ramfs.c b/components/dfs/filesystems/ramfs/dfs_ramfs.c
index 7533b6f192..5143b975f9 100644
--- a/components/dfs/filesystems/ramfs/dfs_ramfs.c
+++ b/components/dfs/filesystems/ramfs/dfs_ramfs.c
@@ -35,20 +35,20 @@ int dfs_ramfs_mount(struct dfs_filesystem *fs,
 {
     struct dfs_ramfs* ramfs;
 
-    if (data == RT_NULL)
-        return -DFS_STATUS_EIO;
+    if (data == NULL)
+        return -EIO;
 
     ramfs = (struct dfs_ramfs *)data;
     fs->data = ramfs;
 
-    return DFS_STATUS_OK;
+    return RT_EOK;
 }
 
 int dfs_ramfs_unmount(struct dfs_filesystem *fs)
 {
-    fs->data = RT_NULL;
+    fs->data = NULL;
 
-    return DFS_STATUS_OK;
+    return RT_EOK;
 }
 
 int dfs_ramfs_statfs(struct dfs_filesystem *fs, struct statfs *buf)
@@ -56,19 +56,19 @@ int dfs_ramfs_statfs(struct dfs_filesystem *fs, struct statfs *buf)
     struct dfs_ramfs *ramfs;
 
     ramfs = (struct dfs_ramfs *)fs->data;
-    RT_ASSERT(ramfs != RT_NULL);
-    RT_ASSERT(buf != RT_NULL);
+    RT_ASSERT(ramfs != NULL);
+    RT_ASSERT(buf != NULL);
 
     buf->f_bsize  = 512;
     buf->f_blocks = ramfs->memheap.pool_size/512;
     buf->f_bfree  = ramfs->memheap.available_size/512;
 
-    return DFS_STATUS_OK;
+    return RT_EOK;
 }
 
 int dfs_ramfs_ioctl(struct dfs_fd *file, int cmd, void *args)
 {
-    return -DFS_STATUS_EIO;
+    return -EIO;
 }
 
 struct ramfs_dirent *dfs_ramfs_lookup(struct dfs_ramfs *ramfs,
@@ -101,16 +101,16 @@ struct ramfs_dirent *dfs_ramfs_lookup(struct dfs_ramfs *ramfs,
     }
 
     /* not found */
-    return RT_NULL;
+    return NULL;
 }
 
-int dfs_ramfs_read(struct dfs_fd *file, void *buf, rt_size_t count)
+int dfs_ramfs_read(struct dfs_fd *file, void *buf, size_t count)
 {
     rt_size_t length;
     struct ramfs_dirent *dirent;
 
     dirent = (struct ramfs_dirent *)file->data;
-    RT_ASSERT(dirent != RT_NULL);
+    RT_ASSERT(dirent != NULL);
 
     if (count < file->size - file->pos)
         length = count;
@@ -126,23 +126,23 @@ int dfs_ramfs_read(struct dfs_fd *file, void *buf, rt_size_t count)
     return length;
 }
 
-int dfs_ramfs_write(struct dfs_fd *fd, const void *buf, rt_size_t count)
+int dfs_ramfs_write(struct dfs_fd *fd, const void *buf, size_t count)
 {
     struct ramfs_dirent *dirent;
     struct dfs_ramfs *ramfs;
 
     ramfs = (struct dfs_ramfs*)fd->fs->data;
-    RT_ASSERT(ramfs != RT_NULL);
+    RT_ASSERT(ramfs != NULL);
     dirent = (struct ramfs_dirent*)fd->data;
-    RT_ASSERT(dirent != RT_NULL);
+    RT_ASSERT(dirent != NULL);
 
     if (count + fd->pos > fd->size)
     {
         rt_uint8_t *ptr;
         ptr = rt_memheap_realloc(&(ramfs->memheap), dirent->data, fd->pos + count);
-        if (ptr == RT_NULL)
+        if (ptr == NULL)
         {
-            rt_set_errno(-RT_ENOMEM);
+            rt_set_errno(-ENOMEM);
 
             return 0;
         }
@@ -162,23 +162,23 @@ int dfs_ramfs_write(struct dfs_fd *fd, const void *buf, rt_size_t count)
     return count;
 }
 
-int dfs_ramfs_lseek(struct dfs_fd *file, rt_off_t offset)
+int dfs_ramfs_lseek(struct dfs_fd *file, off_t offset)
 {
-    if (offset <= (rt_off_t)file->size)
+    if (offset <= (off_t)file->size)
     {
         file->pos = offset;
 
         return file->pos;
     }
 
-    return -DFS_STATUS_EIO;
+    return -EIO;
 }
 
 int dfs_ramfs_close(struct dfs_fd *file)
 {
-    file->data = RT_NULL;
+    file->data = NULL;
 
-    return DFS_STATUS_OK;
+    return RT_EOK;
 }
 
 int dfs_ramfs_open(struct dfs_fd *file)
@@ -188,24 +188,24 @@ int dfs_ramfs_open(struct dfs_fd *file)
     struct ramfs_dirent *dirent;
 
     ramfs = (struct dfs_ramfs *)file->fs->data;
-    RT_ASSERT(ramfs != RT_NULL);
+    RT_ASSERT(ramfs != NULL);
 
-    if (file->flags & DFS_O_DIRECTORY)
+    if (file->flags & O_DIRECTORY)
     {
-        if (file->flags & DFS_O_CREAT)
+        if (file->flags & O_CREAT)
         {
-            return -DFS_STATUS_ENOSPC;
+            return -ENOSPC;
         }
 
         /* open directory */
         dirent = dfs_ramfs_lookup(ramfs, file->path, &size);
-        if (dirent == RT_NULL)
-            return -DFS_STATUS_ENOENT;
+        if (dirent == NULL)
+            return -ENOENT;
         if (dirent == &(ramfs->root)) /* it's root directory */
         {
-            if (!(file->flags & DFS_O_DIRECTORY))
+            if (!(file->flags & O_DIRECTORY))
             {
-                return -DFS_STATUS_ENOENT;
+                return -ENOENT;
             }
         }
     }
@@ -214,12 +214,12 @@ int dfs_ramfs_open(struct dfs_fd *file)
         dirent = dfs_ramfs_lookup(ramfs, file->path, &size);
         if (dirent == &(ramfs->root)) /* it's root directory */
         {
-            return -DFS_STATUS_ENOENT;
+            return -ENOENT;
         }
 
-        if (dirent == RT_NULL)
+        if (dirent == NULL)
         {
-            if (file->flags & DFS_O_CREAT || file->flags & DFS_O_WRONLY)
+            if (file->flags & O_CREAT || file->flags & O_WRONLY)
             {
                 char *name_ptr;
 
@@ -227,9 +227,9 @@ int dfs_ramfs_open(struct dfs_fd *file)
                 dirent = (struct ramfs_dirent *)
                          rt_memheap_alloc(&(ramfs->memheap),
                                           sizeof(struct ramfs_dirent));
-                if (dirent == RT_NULL)
+                if (dirent == NULL)
                 {
-                    return -DFS_STATUS_ENOMEM;
+                    return -ENOMEM;
                 }
 
                 /* remove '/' separator */
@@ -239,37 +239,37 @@ int dfs_ramfs_open(struct dfs_fd *file)
                 strncpy(dirent->name, name_ptr, RAMFS_NAME_MAX);
 
                 rt_list_init(&(dirent->list));
-                dirent->data = RT_NULL;
+                dirent->data = NULL;
                 dirent->size = 0;
                 /* add to the root directory */
                 rt_list_insert_after(&(ramfs->root.list), &(dirent->list));
             }
             else
-                return -DFS_STATUS_ENOENT;
+                return -ENOENT;
         }
 
         /* Creates a new file.
          * If the file is existing, it is truncated and overwritten.
          */
-        if (file->flags & DFS_O_TRUNC)
+        if (file->flags & O_TRUNC)
         {
             dirent->size = 0;
-            if (dirent->data != RT_NULL)
+            if (dirent->data != NULL)
             {
                 rt_memheap_free(dirent->data);
-                dirent->data = RT_NULL;
+                dirent->data = NULL;
             }
         }
     }
 
     file->data = dirent;
     file->size = dirent->size;
-	if (file->flags & DFS_O_APPEND)
+	if (file->flags & O_APPEND)
 		file->pos = file->size;
 	else 
 		file->pos = 0;
 
-    return DFS_STATUS_OK;
+    return 0;
 }
 
 int dfs_ramfs_stat(struct dfs_filesystem *fs,
@@ -283,22 +283,22 @@ int dfs_ramfs_stat(struct dfs_filesystem *fs,
     ramfs = (struct dfs_ramfs *)fs->data;
     dirent = dfs_ramfs_lookup(ramfs, path, &size);
 
-    if (dirent == RT_NULL)
-        return -DFS_STATUS_ENOENT;
+    if (dirent == NULL)
+        return -ENOENT;
 
     st->st_dev = 0;
-    st->st_mode = DFS_S_IFREG | DFS_S_IRUSR | DFS_S_IRGRP | DFS_S_IROTH |
-                  DFS_S_IWUSR | DFS_S_IWGRP | DFS_S_IWOTH;
+    st->st_mode = S_IFREG | S_IRUSR | S_IRGRP | S_IROTH |
+                  S_IWUSR | S_IWGRP | S_IWOTH;
 
     st->st_size = dirent->size;
     st->st_mtime = 0;
 
-    return DFS_STATUS_OK;
+    return RT_EOK;
 }
 
 int dfs_ramfs_getdents(struct dfs_fd *file,
                        struct dirent *dirp,
-                       rt_uint32_t    count)
+                       uint32_t    count)
 {
     rt_size_t index, end;
     struct dirent *d;
@@ -308,12 +308,12 @@ int dfs_ramfs_getdents(struct dfs_fd *file,
     ramfs  = (struct dfs_ramfs *)file->fs->data;
     dirent = (struct ramfs_dirent *)file->data;
     if (dirent != &(ramfs->root))
-        return -DFS_STATUS_EINVAL;
+        return -EINVAL;
 
     /* make integer count */
     count = (count / sizeof(struct dirent));
     if (count == 0)
-        return -DFS_STATUS_EINVAL;
+        return -EINVAL;
 
     end = file->pos + count;
     index = 0;
@@ -346,18 +346,18 @@ int dfs_ramfs_unlink(struct dfs_filesystem *fs, const char *path)
     struct ramfs_dirent *dirent;
 
     ramfs = (struct dfs_ramfs *)fs->data;
-    RT_ASSERT(ramfs != RT_NULL);
+    RT_ASSERT(ramfs != NULL);
 
     dirent = dfs_ramfs_lookup(ramfs, path, &size);
-    if (dirent == RT_NULL)
-        return -DFS_STATUS_ENOENT;
+    if (dirent == NULL)
+        return -ENOENT;
 
     rt_list_remove(&(dirent->list));
-    if (dirent->data != RT_NULL)
+    if (dirent->data != NULL)
         rt_memheap_free(dirent->data);
     rt_memheap_free(dirent);
 
-    return DFS_STATUS_OK;
+    return RT_EOK;
 }
 
 int dfs_ramfs_rename(struct dfs_filesystem *fs,
@@ -369,38 +369,44 @@ int dfs_ramfs_rename(struct dfs_filesystem *fs,
     rt_size_t size;
 
     ramfs = (struct dfs_ramfs *)fs->data;
-    RT_ASSERT(ramfs != RT_NULL);
+    RT_ASSERT(ramfs != NULL);
 
     dirent = dfs_ramfs_lookup(ramfs, newpath, &size);
-    if (dirent != RT_NULL)
-        return -DFS_STATUS_EEXIST;
+    if (dirent != NULL)
+        return -EEXIST;
 
     dirent = dfs_ramfs_lookup(ramfs, oldpath, &size);
-    if (dirent == RT_NULL)
-        return -DFS_STATUS_ENOENT;
+    if (dirent == NULL)
+        return -ENOENT;
 
     strncpy(dirent->name, newpath, RAMFS_NAME_MAX);
 
-    return DFS_STATUS_OK;
+    return RT_EOK;
 }
 
-static const struct dfs_filesystem_operation _ramfs =
+static const struct dfs_file_ops _ram_fops = 
 {
-    "ram",
-    DFS_FS_FLAG_DEFAULT,
-    dfs_ramfs_mount,
-    dfs_ramfs_unmount,
-    RT_NULL, /* mkfs */
-    dfs_ramfs_statfs,
-
     dfs_ramfs_open,
     dfs_ramfs_close,
     dfs_ramfs_ioctl,
     dfs_ramfs_read,
     dfs_ramfs_write,
-    RT_NULL, /* flush */
+    NULL, /* flush */
     dfs_ramfs_lseek,
     dfs_ramfs_getdents,
+};
+
+static const struct dfs_filesystem_ops _ramfs =
+{
+    "ram",
+    DFS_FS_FLAG_DEFAULT,
+    &_ram_fops,
+
+    dfs_ramfs_mount,
+    dfs_ramfs_unmount,
+    NULL, /* mkfs */
+    dfs_ramfs_statfs,
+
     dfs_ramfs_unlink,
     dfs_ramfs_stat,
     dfs_ramfs_rename,
@@ -430,7 +436,7 @@ struct dfs_ramfs* dfs_ramfs_create(rt_uint8_t *pool, rt_size_t size)
 
     result = rt_memheap_init(&ramfs->memheap, "ramfs", data_ptr, size);
     if (result != RT_EOK)
-        return RT_NULL;
+        return NULL;
     /* detach this memheap object from the system */
     rt_object_detach((rt_object_t)&(ramfs->memheap));
 
diff --git a/components/dfs/filesystems/romfs/dfs_romfs.c b/components/dfs/filesystems/romfs/dfs_romfs.c
index 6110d61227..6b9bfa0bce 100644
--- a/components/dfs/filesystems/romfs/dfs_romfs.c
+++ b/components/dfs/filesystems/romfs/dfs_romfs.c
@@ -28,25 +28,25 @@
 
 int dfs_romfs_mount(struct dfs_filesystem *fs, unsigned long rwflag, const void *data)
 {
-	struct romfs_dirent *root_dirent;
+    struct romfs_dirent *root_dirent;
 
-	if (data == RT_NULL)
-		return -DFS_STATUS_EIO;
+    if (data == NULL)
+        return -EIO;
 
-	root_dirent = (struct romfs_dirent *)data;
-	fs->data = root_dirent;
+    root_dirent = (struct romfs_dirent *)data;
+    fs->data = root_dirent;
 
-	return DFS_STATUS_OK;
+    return RT_EOK;
 }
 
 int dfs_romfs_unmount(struct dfs_filesystem *fs)
 {
-	return DFS_STATUS_OK;
+    return RT_EOK;
 }
 
 int dfs_romfs_ioctl(struct dfs_fd *file, int cmd, void *args)
 {
-	return -DFS_STATUS_EIO;
+    return -EIO;
 }
 
 rt_inline int check_dirent(struct romfs_dirent *dirent)
@@ -59,269 +59,274 @@ rt_inline int check_dirent(struct romfs_dirent *dirent)
 
 struct romfs_dirent *dfs_romfs_lookup(struct romfs_dirent *root_dirent, const char *path, rt_size_t *size)
 {
-	rt_size_t index, found;
-	const char *subpath, *subpath_end;
-	struct romfs_dirent *dirent;
-	rt_size_t dirent_size;
+    rt_size_t index, found;
+    const char *subpath, *subpath_end;
+    struct romfs_dirent *dirent;
+    rt_size_t dirent_size;
 
     /* Check the root_dirent. */
     if (check_dirent(root_dirent) != 0)
-        return RT_NULL;
+        return NULL;
 
-	if (path[0] == '/' && path[1] == '\0')
-	{
-		*size = root_dirent->size;
-		return root_dirent;
-	}
+    if (path[0] == '/' && path[1] == '\0')
+    {
+        *size = root_dirent->size;
+        return root_dirent;
+    }
 
-	/* goto root directy entries */
-	dirent = (struct romfs_dirent *)root_dirent->data;
-	dirent_size = root_dirent->size;
+    /* goto root directy entries */
+    dirent = (struct romfs_dirent *)root_dirent->data;
+    dirent_size = root_dirent->size;
 
-	/* get the end position of this subpath */
-	subpath_end = path;
-	/* skip /// */
-	while (*subpath_end && *subpath_end == '/')
-		subpath_end ++;
-	subpath = subpath_end;
-	while ((*subpath_end != '/') && *subpath_end)
-		subpath_end ++;
+    /* get the end position of this subpath */
+    subpath_end = path;
+    /* skip /// */
+    while (*subpath_end && *subpath_end == '/')
+        subpath_end ++;
+    subpath = subpath_end;
+    while ((*subpath_end != '/') && *subpath_end)
+        subpath_end ++;
 
-	while (dirent != RT_NULL)
-	{
-		found = 0;
+    while (dirent != NULL)
+    {
+        found = 0;
 
-		/* search in folder */
-		for (index = 0; index < dirent_size; index ++)
-		{
+        /* search in folder */
+        for (index = 0; index < dirent_size; index ++)
+        {
             if (check_dirent(&dirent[index]) != 0)
-                return RT_NULL;
-			if (rt_strlen(dirent[index].name) == (subpath_end - subpath) &&
-					rt_strncmp(dirent[index].name, subpath, (subpath_end - subpath)) == 0)
-			{
-				dirent_size = dirent[index].size;
+                return NULL;
+            if (rt_strlen(dirent[index].name) == (subpath_end - subpath) &&
+                    rt_strncmp(dirent[index].name, subpath, (subpath_end - subpath)) == 0)
+            {
+                dirent_size = dirent[index].size;
 
-				/* skip /// */
-				while (*subpath_end && *subpath_end == '/')
-					subpath_end ++;
-				subpath = subpath_end;
-				while ((*subpath_end != '/') && *subpath_end)
-					subpath_end ++;
+                /* skip /// */
+                while (*subpath_end && *subpath_end == '/')
+                    subpath_end ++;
+                subpath = subpath_end;
+                while ((*subpath_end != '/') && *subpath_end)
+                    subpath_end ++;
 
-				if (!(*subpath))
-				{
-					*size = dirent_size;
-					return &dirent[index];
-				}
+                if (!(*subpath))
+                {
+                    *size = dirent_size;
+                    return &dirent[index];
+                }
 
-				if (dirent[index].type == ROMFS_DIRENT_DIR)
-				{
-					/* enter directory */
-					dirent = (struct romfs_dirent*)dirent[index].data;
-					found = 1;
-					break;
-				}
-				else
-				{
-					/* return file dirent */
-					if (subpath != RT_NULL)
-						break; /* not the end of path */
+                if (dirent[index].type == ROMFS_DIRENT_DIR)
+                {
+                    /* enter directory */
+                    dirent = (struct romfs_dirent*)dirent[index].data;
+                    found = 1;
+                    break;
+                }
+                else
+                {
+                    /* return file dirent */
+                    if (subpath != NULL)
+                        break; /* not the end of path */
 
-					return &dirent[index];
-				}
-			}
-		}
+                    return &dirent[index];
+                }
+            }
+        }
 
-		if (!found)
-			break; /* not found */
-	}
+        if (!found)
+            break; /* not found */
+    }
 
-	/* not found */
-	return RT_NULL;
+    /* not found */
+    return NULL;
 }
 
-int dfs_romfs_read(struct dfs_fd *file, void *buf, rt_size_t count)
+int dfs_romfs_read(struct dfs_fd *file, void *buf, size_t count)
 {
-	rt_size_t length;
-	struct romfs_dirent *dirent;
+    rt_size_t length;
+    struct romfs_dirent *dirent;
 
-	dirent = (struct romfs_dirent *)file->data;
-	RT_ASSERT(dirent != RT_NULL);
+    dirent = (struct romfs_dirent *)file->data;
+    RT_ASSERT(dirent != NULL);
 
     if (check_dirent(dirent) != 0)
     {
-        return -DFS_STATUS_EIO;
+        return -EIO;
     }
 
-	if (count < file->size - file->pos)
-		length = count;
-	else
-		length = file->size - file->pos;
+    if (count < file->size - file->pos)
+        length = count;
+    else
+        length = file->size - file->pos;
 
-	if (length > 0)
-		memcpy(buf, &(dirent->data[file->pos]), length);
+    if (length > 0)
+        memcpy(buf, &(dirent->data[file->pos]), length);
 
-	/* update file current position */
-	file->pos += length;
+    /* update file current position */
+    file->pos += length;
 
-	return length;
+    return length;
 }
 
-int dfs_romfs_lseek(struct dfs_fd *file, rt_off_t offset)
+int dfs_romfs_lseek(struct dfs_fd *file, off_t offset)
 {
-	if (offset <= file->size)
-	{
-		file->pos = offset;
-		return file->pos;
-	}
+    if (offset <= file->size)
+    {
+        file->pos = offset;
+        return file->pos;
+    }
 
-	return -DFS_STATUS_EIO;
+    return -EIO;
 }
 
 int dfs_romfs_close(struct dfs_fd *file)
 {
-	file->data = RT_NULL;
-	return DFS_STATUS_OK;
+    file->data = NULL;
+    return RT_EOK;
 }
 
 int dfs_romfs_open(struct dfs_fd *file)
 {
-	rt_size_t size;
-	struct romfs_dirent *dirent;
-	struct romfs_dirent *root_dirent;
+    rt_size_t size;
+    struct romfs_dirent *dirent;
+    struct romfs_dirent *root_dirent;
 
-	root_dirent = (struct romfs_dirent *)file->fs->data;
+    root_dirent = (struct romfs_dirent *)file->fs->data;
 
     if (check_dirent(root_dirent) != 0)
-        return -DFS_STATUS_EIO;
+        return -EIO;
 
-	if (file->flags & (DFS_O_CREAT | DFS_O_WRONLY | DFS_O_APPEND | DFS_O_TRUNC | DFS_O_RDWR))
-		return -DFS_STATUS_EINVAL;
+    if (file->flags & (O_CREAT | O_WRONLY | O_APPEND | O_TRUNC | O_RDWR))
+        return -EINVAL;
 
-	dirent = dfs_romfs_lookup(root_dirent, file->path, &size);
-	if (dirent == RT_NULL)
-		return -DFS_STATUS_ENOENT;
+    dirent = dfs_romfs_lookup(root_dirent, file->path, &size);
+    if (dirent == NULL)
+        return -ENOENT;
 
-	/* entry is a directory file type */
-	if (dirent->type == ROMFS_DIRENT_DIR)
-	{
-		if (!(file->flags & DFS_O_DIRECTORY))
-			return -DFS_STATUS_ENOENT;
-	}
-	else
-	{
-		/* entry is a file, but open it as a directory */
-		if (file->flags & DFS_O_DIRECTORY)
-			return -DFS_STATUS_ENOENT;
-	}
+    /* entry is a directory file type */
+    if (dirent->type == ROMFS_DIRENT_DIR)
+    {
+        if (!(file->flags & O_DIRECTORY))
+            return -ENOENT;
+    }
+    else
+    {
+        /* entry is a file, but open it as a directory */
+        if (file->flags & O_DIRECTORY)
+            return -ENOENT;
+    }
 
-	file->data = dirent;
-	file->size = size;
-	file->pos = 0;
+    file->data = dirent;
+    file->size = size;
+    file->pos = 0;
 
-	return DFS_STATUS_OK;
+    return RT_EOK;
 }
 
 int dfs_romfs_stat(struct dfs_filesystem *fs, const char *path, struct stat *st)
 {
-	rt_size_t size;
-	struct romfs_dirent *dirent;
-	struct romfs_dirent *root_dirent;
+    rt_size_t size;
+    struct romfs_dirent *dirent;
+    struct romfs_dirent *root_dirent;
 
-	root_dirent = (struct romfs_dirent *)fs->data;
-	dirent = dfs_romfs_lookup(root_dirent, path, &size);
+    root_dirent = (struct romfs_dirent *)fs->data;
+    dirent = dfs_romfs_lookup(root_dirent, path, &size);
 
-	if (dirent == RT_NULL)
-		return -DFS_STATUS_ENOENT;
+    if (dirent == NULL)
+        return -ENOENT;
 
-	st->st_dev = 0;
-	st->st_mode = DFS_S_IFREG | DFS_S_IRUSR | DFS_S_IRGRP | DFS_S_IROTH |
-	DFS_S_IWUSR | DFS_S_IWGRP | DFS_S_IWOTH;
+    st->st_dev = 0;
+    st->st_mode = S_IFREG | S_IRUSR | S_IRGRP | S_IROTH |
+    S_IWUSR | S_IWGRP | S_IWOTH;
 
-	if (dirent->type == ROMFS_DIRENT_DIR)
-	{
-		st->st_mode &= ~DFS_S_IFREG;
-		st->st_mode |= DFS_S_IFDIR | DFS_S_IXUSR | DFS_S_IXGRP | DFS_S_IXOTH;
-	}
+    if (dirent->type == ROMFS_DIRENT_DIR)
+    {
+        st->st_mode &= ~S_IFREG;
+        st->st_mode |= S_IFDIR | S_IXUSR | S_IXGRP | S_IXOTH;
+    }
 
-	st->st_size = dirent->size;
-	st->st_mtime = 0;
+    st->st_size = dirent->size;
+    st->st_mtime = 0;
 
-	return DFS_STATUS_OK;
+    return RT_EOK;
 }
 
-int dfs_romfs_getdents(struct dfs_fd *file, struct dirent *dirp, rt_uint32_t count)
+int dfs_romfs_getdents(struct dfs_fd *file, struct dirent *dirp, uint32_t count)
 {
-	rt_size_t index;
-	const char *name;
-	struct dirent *d;
-	struct romfs_dirent *dirent, *sub_dirent;
+    rt_size_t index;
+    const char *name;
+    struct dirent *d;
+    struct romfs_dirent *dirent, *sub_dirent;
 
-	dirent = (struct romfs_dirent *)file->data;
+    dirent = (struct romfs_dirent *)file->data;
     if (check_dirent(dirent) != 0)
-        return -DFS_STATUS_EIO;
-	RT_ASSERT(dirent->type == ROMFS_DIRENT_DIR);
+        return -EIO;
+    RT_ASSERT(dirent->type == ROMFS_DIRENT_DIR);
 
-	/* enter directory */
-	dirent = (struct romfs_dirent *)dirent->data;
+    /* enter directory */
+    dirent = (struct romfs_dirent *)dirent->data;
 
-	/* make integer count */
-	count = (count / sizeof(struct dirent));
-	if (count == 0)
-		return -DFS_STATUS_EINVAL;
+    /* make integer count */
+    count = (count / sizeof(struct dirent));
+    if (count == 0)
+        return -EINVAL;
 
-	index = 0;
-	for (index = 0; index < count && file->pos < file->size; index ++)
-	{
-		d = dirp + index;
+    index = 0;
+    for (index = 0; index < count && file->pos < file->size; index ++)
+    {
+        d = dirp + index;
 
-		sub_dirent = &dirent[file->pos];
-		name = sub_dirent->name;
+        sub_dirent = &dirent[file->pos];
+        name = sub_dirent->name;
 
-		/* fill dirent */
-		if (sub_dirent->type == ROMFS_DIRENT_DIR)
-			d->d_type = DFS_DT_DIR;
-		else
-			d->d_type = DFS_DT_REG;
+        /* fill dirent */
+        if (sub_dirent->type == ROMFS_DIRENT_DIR)
+            d->d_type = DT_DIR;
+        else
+            d->d_type = DT_REG;
 
-		d->d_namlen = rt_strlen(name);
-		d->d_reclen = (rt_uint16_t)sizeof(struct dirent);
-		rt_strncpy(d->d_name, name, rt_strlen(name) + 1);
+        d->d_namlen = rt_strlen(name);
+        d->d_reclen = (rt_uint16_t)sizeof(struct dirent);
+        rt_strncpy(d->d_name, name, rt_strlen(name) + 1);
 
-		/* move to next position */
-		++ file->pos;
-	}
+        /* move to next position */
+        ++ file->pos;
+    }
 
-	return index * sizeof(struct dirent);
+    return index * sizeof(struct dirent);
 }
 
-static const struct dfs_filesystem_operation _romfs =
+static const struct dfs_file_ops _rom_fops =
 {
-	"rom",
-	DFS_FS_FLAG_DEFAULT,
-	dfs_romfs_mount,
-	dfs_romfs_unmount,
-	RT_NULL,
-	RT_NULL,
+    dfs_romfs_open,
+    dfs_romfs_close,
+    dfs_romfs_ioctl,
+    dfs_romfs_read,
+    NULL,
+    NULL,
+    dfs_romfs_lseek,
+    dfs_romfs_getdents,
+};
+static const struct dfs_filesystem_ops _romfs =
+{
+    "rom",
+    DFS_FS_FLAG_DEFAULT,
+    &_rom_fops,
 
-	dfs_romfs_open,
-	dfs_romfs_close,
-	dfs_romfs_ioctl,
-	dfs_romfs_read,
-	RT_NULL,
-	RT_NULL,
-	dfs_romfs_lseek,
-	dfs_romfs_getdents,
-	RT_NULL,
-	dfs_romfs_stat,
-	RT_NULL,
+    dfs_romfs_mount,
+    dfs_romfs_unmount,
+    NULL,
+    NULL,
+
+    NULL,
+    dfs_romfs_stat,
+    NULL,
 };
 
 int dfs_romfs_init(void)
 {
     /* register rom file system */
     dfs_register(&_romfs);
-	return 0;
+    return 0;
 }
 INIT_FS_EXPORT(dfs_romfs_init);
 
diff --git a/components/dfs/filesystems/uffs/dfs_uffs.c b/components/dfs/filesystems/uffs/dfs_uffs.c
index ba92452769..7fe7fa3c4f 100644
--- a/components/dfs/filesystems/uffs/dfs_uffs.c
+++ b/components/dfs/filesystems/uffs/dfs_uffs.c
@@ -67,37 +67,37 @@ static int uffs_result_to_dfs(int result)
 		break;
 	case UEACCES:/** Tried to open read-only file for writing, or files sharing mode
 				   does not allow specified operations, or given path is directory */
-		status = -DFS_STATUS_EINVAL;
+		status = -EINVAL;
 		break;/* no suitable */
 	case UEEXIST:   /** _O_CREAT and _O_EXCL flags specified, but filename already exists */
-		status = -DFS_STATUS_EEXIST;
+		status = -EEXIST;
 		break;
 	case UEINVAL:  /** Invalid oflag or pmode argument */
-		status = -DFS_STATUS_EINVAL;
+		status = -EINVAL;
 		break;
 	case UEMFILE: /** No more file handles available(too many open files)  */
 		status = -1;
 		break;
 	case UENOENT: /** file or path not found */
-		status = -DFS_STATUS_ENOENT;
+		status = -ENOENT;
 		break;
 	case UETIME: /** can't set file time */
 		status = -1;
 		break;
 	case UEBADF: /** invalid file handle */
-		status = -DFS_STATUS_EBADF;
+		status = -EBADF;
 		break;
 	case UENOMEM:/** no enough memory */
-		status = -DFS_STATUS_ENOSPC;
+		status = -ENOSPC;
 		break;
 	case UEIOERR: /** I/O error from lower level flash operation */
-		status = -DFS_STATUS_EIO;
+		status = -EIO;
 		break;
 	case UENOTDIR: /** Not a directory */
-		status = -DFS_STATUS_ENOTDIR;
+		status = -ENOTDIR;
 		break;
 	case UEISDIR: /** Is a directory */
-		status = -DFS_STATUS_EISDIR;
+		status = -EISDIR;
 		break;
 	case UEUNKNOWN_ERR:
 	default:
@@ -172,7 +172,7 @@ static int dfs_uffs_mount(
 			break;
 	}
 	if (index == UFFS_DEVICE_MAX)
-		return -DFS_STATUS_ENOENT;
+		return -ENOENT;
 
 	/*2. fill partition structure */
 	nand_part[index].dev = dev;
@@ -216,7 +216,7 @@ static int dfs_uffs_unmount(struct dfs_filesystem* fs)
 			return (result == U_SUCC) ? DFS_STATUS_OK : -1;
 		}
 	}
-	return -DFS_STATUS_ENOENT;
+	return -ENOENT;
 }
 
 static int dfs_uffs_mkfs(rt_device_t dev_id)
@@ -235,7 +235,7 @@ static int dfs_uffs_mkfs(rt_device_t dev_id)
 	if (index == UFFS_DEVICE_MAX)
 	{
 		/* can't find device driver */
-		return -DFS_STATUS_ENOENT;
+		return -ENOENT;
 	}
 
 	/*2. then unmount the partition */
@@ -277,7 +277,7 @@ static int dfs_uffs_statfs(struct dfs_filesystem* fs,
 			break;
 	}
 	if (index == UFFS_DEVICE_MAX)
-		return -DFS_STATUS_ENOENT;
+		return -ENOENT;
 	
 	buf->f_bsize = mtd->page_size*mtd->pages_per_block;
 	buf->f_blocks = (mtd->block_end - mtd->block_start + 1);
@@ -293,11 +293,11 @@ static int dfs_uffs_open(struct dfs_fd* file)
 	char * file_path;
 
 	oflag = file->flags;
-	if (oflag & DFS_O_DIRECTORY)   /* operations about dir */
+	if (oflag & O_DIRECTORY)   /* operations about dir */
 	{
 		uffs_DIR * dir;
 
-		if (oflag & DFS_O_CREAT)   /* create a dir*/
+		if (oflag & O_CREAT)   /* create a dir*/
 		{
 			if (uffs_mkdir(file->path) < 0)
 				return uffs_result_to_dfs(uffs_get_error());
@@ -305,7 +305,7 @@ static int dfs_uffs_open(struct dfs_fd* file)
 		/* open dir */
 		file_path = rt_malloc(FILE_PATH_MAX);
 		if(file_path == RT_NULL)
-			return -DFS_STATUS_ENOMEM;			
+			return -ENOMEM;			
 
 		if (file->path[0] == '/' && !(file->path[1] == 0))
 			rt_snprintf(file_path, FILE_PATH_MAX, "%s/", file->path);
@@ -331,15 +331,15 @@ static int dfs_uffs_open(struct dfs_fd* file)
 	/* int uffs_open(const char *name, int oflag, ...); what is this?
 	 * uffs_open can open dir!!  **/
 	mode = 0;
-	if (oflag & DFS_O_RDONLY) mode |= UO_RDONLY;
-	if (oflag & DFS_O_WRONLY) mode |= UO_WRONLY;
-	if (oflag & DFS_O_RDWR)   mode |= UO_RDWR;
+	if (oflag & O_RDONLY) mode |= UO_RDONLY;
+	if (oflag & O_WRONLY) mode |= UO_WRONLY;
+	if (oflag & O_RDWR)   mode |= UO_RDWR;
 	/* Opens the file, if it is existing. If not, a new file is created. */
-	if (oflag & DFS_O_CREAT) mode |= UO_CREATE;
+	if (oflag & O_CREAT) mode |= UO_CREATE;
 	/* Creates a new file. If the file is existing, it is truncated and overwritten. */
-	if (oflag & DFS_O_TRUNC) mode |= UO_TRUNC;
+	if (oflag & O_TRUNC) mode |= UO_TRUNC;
 	/* Creates a new file. The function fails if the file is already existing. */
-	if (oflag & DFS_O_EXCL) mode |= UO_EXCL;
+	if (oflag & O_EXCL) mode |= UO_EXCL;
 
 	fd = uffs_open(file->path, mode);
 	if (fd < 0)
@@ -355,7 +355,7 @@ static int dfs_uffs_open(struct dfs_fd* file)
 	file->size = uffs_seek(fd, 0, USEEK_END);
 	uffs_seek(fd, file->pos, USEEK_SET);
 
-	if (oflag & DFS_O_APPEND)
+	if (oflag & O_APPEND)
 	{
 		file->pos = uffs_seek(fd, 0, USEEK_END);
 	}
@@ -368,7 +368,7 @@ static int dfs_uffs_close(struct dfs_fd* file)
 	int fd;
 
 	oflag = file->flags;
-	if (oflag & DFS_O_DIRECTORY)
+	if (oflag & O_DIRECTORY)
 	{
 		/* operations about dir */
 		if (uffs_closedir((uffs_DIR *)(file->data)) < 0)
@@ -387,7 +387,7 @@ static int dfs_uffs_close(struct dfs_fd* file)
 
 static int dfs_uffs_ioctl(struct dfs_fd * file, int cmd, void* args)
 {
-	return -DFS_STATUS_ENOSYS;
+	return -ENOSYS;
 }
 
 static int dfs_uffs_read(struct dfs_fd * file, void* buf, rt_size_t len)
@@ -493,12 +493,12 @@ static int dfs_uffs_getdents(
 	
 	/* round count, count is always 1 */
 	count = (count / sizeof(struct dirent)) * sizeof(struct dirent);
-	if (count == 0) return -DFS_STATUS_EINVAL;
+	if (count == 0) return -EINVAL;
 
 	/* allocate file name */
 	file_path = rt_malloc(FILE_PATH_MAX);
 	if (file_path == RT_NULL)
-		return -DFS_STATUS_ENOMEM;
+		return -ENOMEM;
 		
 	index = 0;
 	/* usually, the while loop should only be looped only once! */
@@ -623,7 +623,19 @@ static int dfs_uffs_stat(struct dfs_filesystem* fs, const char *path, struct sta
 	return 0;
 }
 
-static const struct dfs_filesystem_operation dfs_uffs_ops =
+static const struct dfs_file_ops dfs_uffs_fops = 
+{
+	dfs_uffs_open,
+	dfs_uffs_close,
+	dfs_uffs_ioctl,
+	dfs_uffs_read,
+	dfs_uffs_write,
+	dfs_uffs_flush,
+	dfs_uffs_seek,
+	dfs_uffs_getdents,
+};
+
+static const struct dfs_filesystem_ops dfs_uffs_ops =
 {
 	"uffs", /* file system type: uffs */
 #if RTTHREAD_VERSION >= 10100
@@ -631,19 +643,13 @@ static const struct dfs_filesystem_operation dfs_uffs_ops =
 #else
 #error "uffs can only work with rtthread whose version should >= 1.01\n"
 #endif
+	&dfs_uffs_fops,
+
 	dfs_uffs_mount,
 	dfs_uffs_unmount,
 	dfs_uffs_mkfs,
 	dfs_uffs_statfs,
 
-	dfs_uffs_open,
-	dfs_uffs_close,
-	dfs_uffs_ioctl,
-	dfs_uffs_read,
-	dfs_uffs_write,
-	dfs_uffs_flush,
-	dfs_uffs_seek,
-	dfs_uffs_getdents,
 	dfs_uffs_unlink,
 	dfs_uffs_stat,
 	dfs_uffs_rename,
diff --git a/components/dfs/include/dfs.h b/components/dfs/include/dfs.h
index 9ef14d3cfc..f1ea7fa1a4 100644
--- a/components/dfs/include/dfs.h
+++ b/components/dfs/include/dfs.h
@@ -25,17 +25,95 @@
 #ifndef __DFS_H__
 #define __DFS_H__
 
+#include <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
 #include <string.h>
+#include <sys/types.h>
+
+#include <time.h>
+#include <rtthread.h>
+#include <rtdevice.h>
+
+#ifndef DFS_FILESYSTEMS_MAX
+#define DFS_FILESYSTEMS_MAX     2
+#endif
+
+#ifndef DFS_FD_MAX
+#define DFS_FD_MAX              4
+#endif
+
+/*
+ * skip stdin/stdout/stderr normally
+ */
+#ifndef DFS_FD_OFFSET
+#define DFS_FD_OFFSET           3
+#endif
+
+#ifndef DFS_PATH_MAX
+#define DFS_PATH_MAX             256
+#endif
+
+#ifndef SECTOR_SIZE
+#define SECTOR_SIZE              512
+#endif
+
+#ifndef DFS_FILESYSTEM_TYPES_MAX
+#define DFS_FILESYSTEM_TYPES_MAX 2
+#endif
+
+#define DFS_FS_FLAG_DEFAULT     0x00    /* default flag */
+#define DFS_FS_FLAG_FULLPATH    0x01    /* set full path to underlaying file system */
+
+/* File types */
+#define FT_REGULAR               0   /* regular file */
+#define FT_SOCKET                1   /* socket file  */
+#define FT_DIRECTORY             2   /* directory    */
+#define FT_USER                  3   /* user defined */
+
+/* File flags */
+#define DFS_F_OPEN              0x01000000
+#define DFS_F_DIRECTORY         0x02000000
+#define DFS_F_EOF               0x04000000
+#define DFS_F_ERR               0x08000000
 
 #ifdef __cplusplus
 extern "C" {
 #endif
 
-#define NO_WORKING_DIR  "system does not support working directory\n"
+struct stat
+{
+    struct rt_device* st_dev;
+    uint16_t st_mode;
+    uint32_t st_size;
+    time_t   st_mtime;
+    uint32_t st_blksize;
+};
+
+struct statfs
+{
+    size_t f_bsize;   /* block size */
+    size_t f_blocks;  /* total data blocks in file system */
+    size_t f_bfree;   /* free blocks in file system */
+};
+
+struct dirent
+{
+    uint8_t d_type;           /* The type of the file */
+    uint8_t d_namlen;         /* The length of the not including the terminating null file name */
+    uint16_t d_reclen;        /* length of this record */
+    char d_name[DFS_PATH_MAX];   /* The null-terminated file name */
+};
+
+/* Initialization of dfs */
+int dfs_init(void);
 
 char *dfs_normalize_path(const char *directory, const char *filename);
 const char *dfs_subdir(const char *directory, const char *filename);
 
+void dfs_lock(void);
+void dfs_unlock(void);
+
 /* FD APIs */
 int fd_new(void);
 struct dfs_fd *fd_get(int fd);
diff --git a/components/dfs/include/dfs_def.h b/components/dfs/include/dfs_def.h
deleted file mode 100644
index 0f75a5162b..0000000000
--- a/components/dfs/include/dfs_def.h
+++ /dev/null
@@ -1,316 +0,0 @@
-/*
- * File      : dfs_def.h
- * This file is part of Device File System in RT-Thread RTOS
- * COPYRIGHT (C) 2004-2012, RT-Thread Development Team
- *
- *  This program is free software; you can redistribute it and/or modify
- *  it under the terms of the GNU General Public License as published by
- *  the Free Software Foundation; either version 2 of the License, or
- *  (at your option) any later version.
- *
- *  This program is distributed in the hope that it will be useful,
- *  but WITHOUT ANY WARRANTY; without even the implied warranty of
- *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- *  GNU General Public License for more details.
- *
- *  You should have received a copy of the GNU General Public License along
- *  with this program; if not, write to the Free Software Foundation, Inc.,
- *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
- *
- * Change Logs:
- * Date           Author       Notes
- * 2004-10-01     Beranard     The first version.
- * 2004-10-14     Beranard     Clean up the code.
- * 2005-01-22     Beranard     Clean up the code, port to MinGW
- */
- 
-#ifndef __DFS_DEF_H__
-#define __DFS_DEF_H__
-
-#include <rtthread.h>
-
-#ifndef __D_FS__
-#define __D_FS__
-#endif
-
-#define DEVICE_GETGEOME          0
-#define DEVICE_GETINFO           1
-#define DEVICE_FORMAT            2
-#define DEVICE_CLEAN_SECTOR      3
-
-/* File flags */
-#define DFS_F_OPEN               0x01000000
-#define DFS_F_DIRECTORY          0x02000000
-#define DFS_F_EOF                0x04000000
-#define DFS_F_ERR                0x08000000
-
-#ifndef DFS_PATH_MAX
-#define DFS_PATH_MAX             256
-#endif
-
-#ifndef SECTOR_SIZE
-#define SECTOR_SIZE              512
-#endif
-
-#ifndef DFS_FILESYSTEM_TYPES_MAX
-#define DFS_FILESYSTEM_TYPES_MAX 4
-#endif
-
-#define DFS_DEBUG_INFO           0x01
-#define DFS_DEBUG_WARNING        0x02
-#define DFS_DEBUG_ERROR          0x04
-#define DFS_DEBUG_LEVEL          (DFS_DEBUG_INFO | DFS_DEBUG_WARNING | DFS_DEBUG_ERROR)
-
-/* #define DFS_DEBUG */
-#ifdef DFS_DEBUG
-#define dfs_log(level, x)        do { if (level & DFS_DEBUG_LEVEL)      \
-    {rt_kprintf("DFS %s, %d:", __FUNCTION__, __LINE__); rt_kprintf x;   \
-    rt_kprintf ("\n");}}while (0)
-#else
-#define dfs_log(level, x)
-#endif
-
-#if defined(RT_USING_NEWLIB) 
-#include <string.h>
-#include <sys/stat.h>            /* used for struct stat */
-#include <sys/statfs.h>          /* used for struct statfs */
-#include <sys/errno.h>           /* used for error number */
-#include <sys/fcntl.h>           /* used for operation flags */
-#include <sys/unistd.h>          /* used for SEEK_SET/CUR/END */
-#include <dirent.h>              /* used for struct dirent */
-
-/* Device error codes */
-#define DFS_STATUS_OK            0           /* no error */
-#define DFS_STATUS_ENOENT        ENOENT      /* No such file or directory */
-#define DFS_STATUS_EIO           EIO         /* I/O error */
-#define DFS_STATUS_ENXIO         ENXIO       /* No such device or address */
-#define DFS_STATUS_EBADF         EBADF       /* Bad file number */
-#define DFS_STATUS_EAGAIN        EAGAIN      /* Try again */
-#define DFS_STATUS_ENOMEM        ENOMEM      /* no memory */
-#define DFS_STATUS_EBUSY         EBUSY       /* Device or resource busy */
-#define DFS_STATUS_EEXIST        EEXIST      /* File exists */
-#define DFS_STATUS_EXDEV         EXDEV       /* Cross-device link */
-#define DFS_STATUS_ENODEV        ENODEV      /* No such device */
-#define DFS_STATUS_ENOTDIR       ENOTDIR     /* Not a directory */
-#define DFS_STATUS_EISDIR        EISDIR      /* Is a directory */
-#define DFS_STATUS_EINVAL        EINVAL      /* Invalid argument */
-#define DFS_STATUS_ENOSPC        ENOSPC      /* No space left on device */
-#define DFS_STATUS_EROFS         EROFS       /* Read-only file system */
-#define DFS_STATUS_ENOSYS        ENOSYS      /* Function not implemented */
-#define DFS_STATUS_ENOTEMPTY     ENOTEMPTY   /* Directory not empty */
-
-/* Operation flags */
-#define DFS_O_RDONLY             O_RDONLY
-#define DFS_O_WRONLY             O_WRONLY
-#define DFS_O_RDWR               O_RDWR
-#define DFS_O_ACCMODE            O_ACCMODE
-#define DFS_O_CREAT              O_CREAT
-#define DFS_O_EXCL               O_EXCL
-#define DFS_O_TRUNC              O_TRUNC
-#define DFS_O_APPEND             O_APPEND
-#define DFS_O_DIRECTORY          O_DIRECTORY
-
-/* Seek flags */
-#define DFS_SEEK_SET             SEEK_SET
-#define DFS_SEEK_CUR             SEEK_CUR
-#define DFS_SEEK_END             SEEK_END
-
-/* Stat codes */
-#define DFS_S_IFMT               S_IFMT
-#define DFS_S_IFSOCK             S_IFSOCK
-#define DFS_S_IFLNK              S_IFLNK
-#define DFS_S_IFREG              S_IFREG
-#define DFS_S_IFBLK              S_IFBLK
-#define DFS_S_IFDIR              S_IFDIR
-#define DFS_S_IFCHR              S_IFCHR
-#define DFS_S_IFIFO              S_IFIFO
-#define DFS_S_ISUID              S_ISUID
-#define DFS_S_ISGID              S_ISGID
-#define DFS_S_ISVTX              S_ISVTX
-
-#define DFS_S_ISLNK(m)           S_ISLNK(m)
-#define DFS_S_ISREG(m)           S_ISREG(m)
-#define DFS_S_ISDIR(m)           S_ISDIR(m)
-#define DFS_S_ISCHR(m)           S_ISCHR(m)
-#define DFS_S_ISBLK(m)           S_ISBLK(m)
-#define DFS_S_ISFIFO(m)          S_ISFIFO(m)
-#define DFS_S_ISSOCK(m)          S_ISSOCK(m)
-
-#define DFS_S_IRWXU              S_IRWXU
-#define DFS_S_IRUSR              S_IRUSR
-#define DFS_S_IWUSR              S_IWUSR
-#define DFS_S_IXUSR              S_IXUSR
-
-#define DFS_S_IRWXG              S_IRWXG
-#define DFS_S_IRGRP              S_IRGRP
-#define DFS_S_IWGRP              S_IWGRP
-#define DFS_S_IXGRP              S_IXGRP
-
-#define DFS_S_IRWXO              S_IRWXO
-#define DFS_S_IROTH              S_IROTH
-#define DFS_S_IWOTH              S_IWOTH
-#define DFS_S_IXOTH              S_IXOTH
-
-/* Dirent types */
-#define DFS_DT_UNKNOWN           DT_UNKNOWN
-#define DFS_DT_REG               DT_REG
-#define DFS_DT_DIR               DT_DIR
-
-#else
-    #ifdef RT_USING_MINILIBC
-        #include <string.h>
-    #else
-        typedef long off_t;
-        typedef int mode_t;
-    #endif
-
-/* Device error codes */
-#define DFS_STATUS_OK            0       /* no error */
-#define DFS_STATUS_ENOENT        2       /* No such file or directory */
-#define DFS_STATUS_EIO           5       /* I/O error */
-#define DFS_STATUS_ENXIO         6       /* No such device or address */
-#define DFS_STATUS_EBADF         9       /* Bad file number */
-#define DFS_STATUS_EAGAIN        11      /* Try again */
-#define DFS_STATUS_ENOMEM        12      /* no memory */
-#define DFS_STATUS_EBUSY         16      /* Device or resource busy */
-#define DFS_STATUS_EEXIST        17      /* File exists */
-#define DFS_STATUS_EXDEV         18      /* Cross-device link */
-#define DFS_STATUS_ENODEV        19      /* No such device */
-#define DFS_STATUS_ENOTDIR       20      /* Not a directory */
-#define DFS_STATUS_EISDIR        21      /* Is a directory */
-#define DFS_STATUS_EINVAL        22      /* Invalid argument */
-#define DFS_STATUS_ENOSPC        28      /* No space left on device */
-#define DFS_STATUS_EROFS         30      /* Read-only file system */
-#define DFS_STATUS_ENOSYS        38      /* Function not implemented */
-#define DFS_STATUS_ENOTEMPTY     39      /* Directory not empty */
-
-/* Operation flags */
-#define DFS_O_RDONLY             0x0000000
-#define DFS_O_WRONLY             0x0000001
-#define DFS_O_RDWR               0x0000002
-#define DFS_O_ACCMODE            0x0000003
-#define DFS_O_CREAT              0x0000100
-#define DFS_O_EXCL               0x0000200
-#define DFS_O_TRUNC              0x0001000
-#define DFS_O_APPEND             0x0002000
-#define DFS_O_BINARY             0x0008000
-#define DFS_O_DIRECTORY          0x0200000
-
-/* File flags */
-#define DFS_F_OPEN               0x01000000
-#define DFS_F_DIRECTORY          0x02000000
-#define DFS_F_EOF                0x04000000
-#define DFS_F_ERR                0x08000000
-
-/* Seek flags */
-#ifdef __CC_ARM
-#include <stdio.h>
-#define DFS_SEEK_SET             SEEK_SET
-#define DFS_SEEK_CUR             SEEK_CUR
-#define DFS_SEEK_END             SEEK_END
-#elif defined(_MSC_VER)
-#include <stdio.h>
-#define DFS_SEEK_SET             SEEK_SET
-#define DFS_SEEK_CUR             SEEK_CUR
-#define DFS_SEEK_END             SEEK_END
-#else
-#define DFS_SEEK_SET             0
-#define DFS_SEEK_CUR             1
-#define DFS_SEEK_END             2
-#endif
-
-/* Stat codes */
-#define DFS_S_IFMT               00170000
-#define DFS_S_IFSOCK             0140000
-#define DFS_S_IFLNK              0120000
-#define DFS_S_IFREG              0100000
-#define DFS_S_IFBLK              0060000
-#define DFS_S_IFDIR              0040000
-#define DFS_S_IFCHR              0020000
-#define DFS_S_IFIFO              0010000
-#define DFS_S_ISUID              0004000
-#define DFS_S_ISGID              0002000
-#define DFS_S_ISVTX              0001000
-
-#define DFS_S_ISLNK(m)           (((m) & DFS_S_IFMT) == DFS_S_IFLNK)
-#define DFS_S_ISREG(m)           (((m) & DFS_S_IFMT) == DFS_S_IFREG)
-#define DFS_S_ISDIR(m)           (((m) & DFS_S_IFMT) == DFS_S_IFDIR)
-#define DFS_S_ISCHR(m)           (((m) & DFS_S_IFMT) == DFS_S_IFCHR)
-#define DFS_S_ISBLK(m)           (((m) & DFS_S_IFMT) == DFS_S_IFBLK)
-#define DFS_S_ISFIFO(m)          (((m) & DFS_S_IFMT) == DFS_S_IFIFO)
-#define DFS_S_ISSOCK(m)          (((m) & DFS_S_IFMT) == DFS_S_IFSOCK)
-
-#define DFS_S_IRWXU              00700
-#define DFS_S_IRUSR              00400
-#define DFS_S_IWUSR              00200
-#define DFS_S_IXUSR              00100
-
-#define DFS_S_IRWXG              00070
-#define DFS_S_IRGRP              00040
-#define DFS_S_IWGRP              00020
-#define DFS_S_IXGRP              00010
-
-#define DFS_S_IRWXO              00007
-#define DFS_S_IROTH              00004
-#define DFS_S_IWOTH              00002
-#define DFS_S_IXOTH              00001
-
-#ifdef _MSC_VER
-#include <wchar.h>
-#else
-struct stat
-{
-    rt_device_t st_dev;
-    rt_uint16_t st_mode;
-    rt_uint32_t st_size;
-    rt_time_t   st_mtime;
-};
-#endif
-
-struct statfs
-{
-    rt_size_t f_bsize;   /* block size */
-    rt_size_t f_blocks;  /* total data blocks in file system */
-    rt_size_t f_bfree;   /* free blocks in file system */
-};
-
-/* File types */
-#define FT_REGULAR               0   /* regular file */
-#define FT_SOCKET                1   /* socket file  */
-#define FT_DIRECTORY             2   /* directory    */
-#define FT_USER                  3   /* user defined */
-
-/* Dirent types */
-#define DFS_DT_UNKNOWN           0x00
-#define DFS_DT_REG               0x01
-#define DFS_DT_DIR               0x02
-
-struct dirent
-{
-    rt_uint8_t d_type;           /* The type of the file */
-    rt_uint8_t d_namlen;         /* The length of the not including the terminating null file name */
-    rt_uint16_t d_reclen;        /* length of this record */
-    char d_name[DFS_PATH_MAX];   /* The null-terminated file name */
-};
-#endif
-
-/* file descriptor */
-#define DFS_FD_MAGIC	 0xfdfd
-struct dfs_fd
-{
-    rt_uint16_t magic;           /* file descriptor magic number */
-    rt_uint16_t type;            /* Type (regular or socket) */
-    char *path;                  /* Name (below mount point) */
-    int ref_count;               /* Descriptor reference count */
-
-    struct dfs_filesystem *fs;   /* Resident file system */
-
-    rt_uint32_t flags;           /* Descriptor flags */
-    rt_size_t   size;            /* Size in bytes */
-    rt_off_t    pos;             /* Current file position */
-
-    void *data;                  /* Specific file system data */
-};
-
-#endif
-
diff --git a/components/dfs/include/dfs_file.h b/components/dfs/include/dfs_file.h
index a574bdc334..5dc3946899 100644
--- a/components/dfs/include/dfs_file.h
+++ b/components/dfs/include/dfs_file.h
@@ -25,21 +25,63 @@
 #ifndef __DFS_FILE_H__
 #define __DFS_FILE_H__
 
-#include <dfs_def.h>
 #include <dfs.h>
 #include <dfs_fs.h>
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+struct rt_pollreq;
+
+struct dfs_file_ops
+{
+    int (*open)     (struct dfs_fd *fd);
+    int (*close)    (struct dfs_fd *fd);
+    int (*ioctl)    (struct dfs_fd *fd, int cmd, void *args);
+    int (*read)     (struct dfs_fd *fd, void *buf, size_t count);
+    int (*write)    (struct dfs_fd *fd, const void *buf, size_t count);
+    int (*flush)    (struct dfs_fd *fd);
+    int (*lseek)    (struct dfs_fd *fd, off_t offset);
+    int (*getdents) (struct dfs_fd *fd, struct dirent *dirp, uint32_t count);
+
+    int (*poll)     (struct dfs_fd *fd, struct rt_pollreq *req);
+};
+
+/* file descriptor */
+#define DFS_FD_MAGIC     0xfdfd
+struct dfs_fd
+{
+    uint16_t magic;              /* file descriptor magic number */
+    uint16_t type;               /* Type (regular or socket) */
+
+    char *path;                  /* Name (below mount point) */
+    int ref_count;               /* Descriptor reference count */
+
+    const struct dfs_file_ops *fops;
+
+    uint32_t flags;              /* Descriptor flags */
+    size_t   size;               /* Size in bytes */
+    off_t    pos;                /* Current file position */
+
+    void *data;                  /* Specific file system data */
+};
+
 int dfs_file_open(struct dfs_fd *fd, const char *path, int flags);
 int dfs_file_close(struct dfs_fd *fd);
 int dfs_file_ioctl(struct dfs_fd *fd, int cmd, void *args);
-int dfs_file_read(struct dfs_fd *fd, void *buf, rt_size_t len);
-int dfs_file_getdents(struct dfs_fd *fd, struct dirent *dirp, rt_size_t nbytes);
+int dfs_file_read(struct dfs_fd *fd, void *buf, size_t len);
+int dfs_file_getdents(struct dfs_fd *fd, struct dirent *dirp, size_t nbytes);
 int dfs_file_unlink(const char *path);
-int dfs_file_write(struct dfs_fd *fd, const void *buf, rt_size_t len);
+int dfs_file_write(struct dfs_fd *fd, const void *buf, size_t len);
 int dfs_file_flush(struct dfs_fd *fd);
-int dfs_file_lseek(struct dfs_fd *fd, rt_off_t offset);
+int dfs_file_lseek(struct dfs_fd *fd, off_t offset);
+
 int dfs_file_stat(const char *path, struct stat *buf);
 int dfs_file_rename(const char *oldpath, const char *newpath);
 
+#ifdef __cplusplus
+}
 #endif
 
+#endif
diff --git a/components/dfs/include/dfs_fs.h b/components/dfs/include/dfs_fs.h
index 498aa5db54..38d8766ee1 100644
--- a/components/dfs/include/dfs_fs.h
+++ b/components/dfs/include/dfs_fs.h
@@ -25,20 +25,24 @@
 #ifndef __DFS_FS_H__
 #define __DFS_FS_H__
 
-#include <dfs_def.h>
+#include <dfs.h>
 
-#define DFS_FS_FLAG_DEFAULT     0x00    /* default flag */
-#define DFS_FS_FLAG_FULLPATH    0x01    /* set full path to underlaying file system */
+#ifdef __cplusplus
+extern "C" {
+#endif
 
 /* Pre-declaration */
 struct dfs_filesystem;
 struct dfs_fd;
 
-/* File system operations struct */
-struct dfs_filesystem_operation
+/* File system operations */
+struct dfs_filesystem_ops
 {
     char *name;
-    rt_uint32_t flags;      /* flags for file system operations */
+    uint32_t flags;      /* flags for file system operations */
+
+    /* operations for file */
+    const struct dfs_file_ops *fops;
 
     /* mount and unmount file system */
     int (*mount)    (struct dfs_filesystem *fs, unsigned long rwflag, const void *data);
@@ -48,15 +52,6 @@ struct dfs_filesystem_operation
     int (*mkfs)     (rt_device_t devid);
     int (*statfs)   (struct dfs_filesystem *fs, struct statfs *buf);
 
-    int (*open)     (struct dfs_fd *fd);
-    int (*close)    (struct dfs_fd *fd);
-    int (*ioctl)    (struct dfs_fd *fd, int cmd, void *args);
-    int (*read)     (struct dfs_fd *fd, void *buf, rt_size_t count);
-    int (*write)    (struct dfs_fd *fd, const void *buf, rt_size_t count);
-    int (*flush)    (struct dfs_fd *fd);
-    int (*lseek)    (struct dfs_fd *fd, rt_off_t offset);
-    int (*getdents) (struct dfs_fd *fd, struct dirent *dirp, rt_uint32_t count);
-
     int (*unlink)   (struct dfs_filesystem *fs, const char *pathname);
     int (*stat)     (struct dfs_filesystem *fs, const char *filename, struct stat *buf);
     int (*rename)   (struct dfs_filesystem *fs, const char *oldpath, const char *newpath);
@@ -68,7 +63,7 @@ struct dfs_filesystem
     rt_device_t dev_id;     /* Attached device */
 
     char *path;             /* File system mount point */
-    const struct dfs_filesystem_operation *ops; /* Operations for file system type */
+    const struct dfs_filesystem_ops *ops; /* Operations for file system type */
 
     void *data;             /* Specific file system data */
 };
@@ -76,47 +71,42 @@ struct dfs_filesystem
 /* file system partition table */
 struct dfs_partition
 {
-    rt_uint8_t type;        /* file system type */
-    rt_off_t  offset;       /* partition start offset */
-    rt_size_t size;         /* partition size */
+    uint8_t type;        /* file system type */
+    off_t  offset;       /* partition start offset */
+    size_t size;         /* partition size */
     rt_sem_t lock;  
 };
 
 /* mount table */
 struct dfs_mount_tbl
 {
-	const char	 *device_name;
-	const char   *path;
-	const char   *filesystemtype;
-	unsigned long rwflag;
-	const void   *data;
+    const char   *device_name;
+    const char   *path;
+    const char   *filesystemtype;
+    unsigned long rwflag;
+    const void   *data;
 };
 
-int dfs_register(const struct dfs_filesystem_operation *ops);
+int dfs_register(const struct dfs_filesystem_ops *ops);
 struct dfs_filesystem *dfs_filesystem_lookup(const char *path);
 const char* dfs_filesystem_get_mounted_path(struct rt_device* device);
 
-rt_err_t dfs_filesystem_get_partition(struct dfs_partition *part,
-                                      rt_uint8_t           *buf,
-                                      rt_uint32_t           pindex);
+int dfs_filesystem_get_partition(struct dfs_partition *part,
+                                      uint8_t         *buf,
+                                      uint32_t        pindex);
 
 int dfs_mount(const char *device_name,
               const char *path,
               const char *filesystemtype,
-              rt_uint32_t rwflag,
+              unsigned long rwflag,
               const void *data);
 int dfs_unmount(const char *specialfile);
 
-/* extern variable */
-extern const struct dfs_filesystem_operation *filesystem_operation_table[];
-extern struct dfs_filesystem filesystem_table[];
-extern const struct dfs_mount_tbl mount_table[];
-
-extern char working_directory[];
-
-void dfs_lock(void);
-void dfs_unlock(void);
 int dfs_mkfs(const char *fs_name, const char *device_name);
 int dfs_statfs(const char *path, struct statfs *buffer);
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif
diff --git a/components/dfs/include/dfs_init.h b/components/dfs/include/dfs_init.h
deleted file mode 100644
index b421bdcb04..0000000000
--- a/components/dfs/include/dfs_init.h
+++ /dev/null
@@ -1,39 +0,0 @@
-/*
- * File      : dfs_init.h
- * This file is part of Device File System in RT-Thread RTOS
- * COPYRIGHT (C) 2004-2012, RT-Thread Development Team
- *
- *  This program is free software; you can redistribute it and/or modify
- *  it under the terms of the GNU General Public License as published by
- *  the Free Software Foundation; either version 2 of the License, or
- *  (at your option) any later version.
- *
- *  This program is distributed in the hope that it will be useful,
- *  but WITHOUT ANY WARRANTY; without even the implied warranty of
- *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- *  GNU General Public License for more details.
- *
- *  You should have received a copy of the GNU General Public License along
- *  with this program; if not, write to the Free Software Foundation, Inc.,
- *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
- *
- * Change Logs:
- * Date           Author       Notes
- * 2005-02-21     Bernard      The first version.
- */
-
-#ifndef __DFS_INIT_H__
-#define __DFS_INIT_H__
-
-#ifdef __cplusplus
-extern "C" {
-#endif
-
-/* Initialization of dfs */
-int dfs_init(void);
-
-#ifdef __cplusplus
-}
-#endif
-
-#endif
diff --git a/components/dfs/include/dfs_posix.h b/components/dfs/include/dfs_posix.h
index 2e417c1461..e775474f0a 100644
--- a/components/dfs/include/dfs_posix.h
+++ b/components/dfs/include/dfs_posix.h
@@ -20,81 +20,21 @@
  * Change Logs:
  * Date           Author       Notes
  * 2009-05-27     Yi.qiu       The first version.
- * 2010-07-18     Bernard      add stat and statfs structure definitions. 
+ * 2010-07-18     Bernard      add stat and statfs structure definitions.
  * 2011-05-16     Yi.qiu       Change parameter name of rename, "new" is C++ key word.
  */
- 
+
 #ifndef __DFS_POSIX_H__
 #define __DFS_POSIX_H__
 
 #include <dfs_file.h>
-#include <dfs_def.h>
+#include <sys/time.h> /* for struct timeval */
 
 #ifdef __cplusplus
 extern "C" {
 #endif
 
-#if !defined(RT_USING_NEWLIB)
-#define O_RDONLY    DFS_O_RDONLY
-#define O_WRONLY    DFS_O_WRONLY
-#define O_RDWR      DFS_O_RDWR
-#define O_ACCMODE   DFS_O_ACCMODE
-#define O_CREAT     DFS_O_CREAT
-#define O_EXCL      DFS_O_EXCL
-#define O_TRUNC     DFS_O_TRUNC
-#define O_APPEND    DFS_O_APPEND
-#define O_BINARY    DFS_O_BINARY
-#define O_DIRECTORY DFS_O_DIRECTORY
-
-#if !defined(_WIN32)
-#define S_IFMT      DFS_S_IFMT
-#define S_IFSOCK    DFS_S_IFSOCK
-#define S_IFLNK     DFS_S_IFLNK 
-#define S_IFREG     DFS_S_IFREG 
-#define S_IFBLK     DFS_S_IFBLK 
-#define S_IFDIR     DFS_S_IFDIR 
-#define S_IFCHR     DFS_S_IFCHR 
-#define S_IFIFO     DFS_S_IFIFO 
-#define S_ISUID     DFS_S_ISUID 
-#define S_ISGID     DFS_S_ISGID 
-#define S_ISVTX     DFS_S_ISVTX 
-
-#define S_ISLNK(m)  (((m) & DFS_S_IFMT) == DFS_S_IFLNK)
-#define S_ISREG(m)  (((m) & DFS_S_IFMT) == DFS_S_IFREG)
-#define S_ISDIR(m)  (((m) & DFS_S_IFMT) == DFS_S_IFDIR)
-#define S_ISCHR(m)  (((m) & DFS_S_IFMT) == DFS_S_IFCHR)
-#define S_ISBLK(m)  (((m) & DFS_S_IFMT) == DFS_S_IFBLK)
-#define S_ISFIFO(m) (((m) & DFS_S_IFMT) == DFS_S_IFIFO)
-#define S_ISSOCK(m) (((m) & DFS_S_IFMT) == DFS_S_IFSOCK)
-
-#define S_IRWXU     DFS_S_IRWXU
-#define S_IRUSR     DFS_S_IRUSR
-#define S_IWUSR     DFS_S_IWUSR
-#define S_IXUSR     DFS_S_IXUSR
-
-#define S_IRWXG     DFS_S_IRWXG
-#define S_IRGRP     DFS_S_IRGRP
-#define S_IWGRP     DFS_S_IWGRP
-#define S_IXGRP     DFS_S_IXGRP
-
-#define S_IRWXO     DFS_S_IRWXO
-#define S_IROTH     DFS_S_IROTH
-#define S_IWOTH     DFS_S_IWOTH
-#define S_IXOTH     DFS_S_IXOTH
-#endif
-
-#if defined(__CC_ARM)
-#include <stdio.h>
-#include <stdlib.h>
-#elif defined(_MSC_VER)
-#include <stdio.h>
-#else
-#define SEEK_SET    DFS_SEEK_SET
-#define SEEK_CUR    DFS_SEEK_CUR
-#define SEEK_END    DFS_SEEK_END
-#endif
-
-typedef struct 
+typedef struct
 {
     int fd;     /* directory file */
     char buf[512];
@@ -111,13 +51,6 @@ void seekdir(DIR *d, off_t offset);
 void rewinddir(DIR *d);
 int closedir(DIR* d);
 
-#else
-/* use newlib header file */
-#include <sys/stat.h>
-#endif
-
-struct stat;
-
 /* file api*/
 int open(const char *file, int flags, int mode);
 int close(int d);
@@ -134,7 +67,7 @@ int unlink(const char *pathname);
 int stat(const char *file, struct stat *buf);
 int fstat(int fildes, struct stat *buf);
 int fsync(int fildes);
-int ioctl(int fildes, long cmd, void *data);
+int ioctl(int fildes, int cmd, void *data);
 
 /* directory api*/
 int rmdir(const char *path);
@@ -144,6 +77,100 @@ char *getcwd(char *buf, size_t size);
 /* file system api */
 int statfs(const char *path, struct statfs *buf);
 
+int access(const char *path, int amode);
+int pipe(int fildes[2]);
+int mkfifo(const char *path, mode_t mode);
+
+/* poll and select */
+
+#define POLLIN          (0x01)
+#define POLLRDNORM      (0x01)
+#define POLLRDBAND      (0x01)
+#define POLLPRI         (0x01)
+
+#define POLLOUT         (0x02)
+#define POLLWRNORM      (0x02)
+#define POLLWRBAND      (0x02)
+
+#define POLLERR         (0x04)
+#define POLLHUP         (0x08)
+#define POLLNVAL        (0x10)
+
+#define POLLMASK_DEFAULT (POLLIN | POLLOUT | POLLRDNORM | POLLWRNORM)
+
+typedef unsigned int nfds_t;
+
+struct pollfd
+{
+    int fd;
+    short events;
+    short revents;
+};
+
+int poll(struct pollfd *fds, nfds_t nfds, int timeout);
+
+
+#ifdef RT_USING_LWIP
+/* we use lwIP's structure definitions. */
+#include <lwip/sockets.h>
+#else
+
+#ifndef FD_SET
+
+/* Get the total number of descriptors that we will have to support */
+
+#define FD_SETSIZE (12)
+
+/* We will use a 32-bit bitsets to represent the set of descriptors.  How
+ * many uint32_t's do we need to span all descriptors?
+ */
+
+#if FD_SETSIZE <= 32
+#  define __SELECT_NUINT32 1
+#elif FD_SETSIZE <= 64
+#  define __SELECT_NUINT32 2
+#elif FD_SETSIZE <= 96
+#  define __SELECT_NUINT32 3
+#elif FD_SETSIZE <= 128
+#  define __SELECT_NUINT32 4
+#elif FD_SETSIZE <= 160
+#  define __SELECT_NUINT32 5
+#elif FD_SETSIZE <= 192
+#  define __SELECT_NUINT32 6
+#elif FD_SETSIZE <= 224
+#  define __SELECT_NUINT32 7
+#elif FD_SETSIZE <= 256
+#  define __SELECT_NUINT32 8
+#else
+#  warning "Larger fd_set needed"
+#endif
+
+/* These macros map a file descriptor to an index and bit number */
+
+#define _FD_NDX(fd)    ((fd) >> 5)
+#define _FD_BIT(fd)      ((fd) & 0x1f)
+
+/* Standard helper macros */
+
+#define FD_CLR(fd,set) \
+  ((((fd_set*)(set))->arr)[_FD_NDX(fd)] &= ~(1 << _FD_BIT(fd)))
+#define FD_SET(fd,set) \
+  ((((fd_set*)(set))->arr)[_FD_NDX(fd)] |= (1 << _FD_BIT(fd)))
+#define FD_ISSET(fd,set) \
+  (((((fd_set*)(set))->arr)[_FD_NDX(fd)] & (1 << _FD_BIT(fd))) != 0)
+#define FD_ZERO(set) \
+   memset((set), 0, sizeof(fd_set))
+
+typedef struct
+{
+    uint32_t arr[__SELECT_NUINT32];
+}fd_set;
+#endif
+
+#endif
+
+int select(int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds, struct timeval *timeout);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/components/dfs/include/dfs_private.h b/components/dfs/include/dfs_private.h
new file mode 100644
index 0000000000..d5d630b47e
--- /dev/null
+++ b/components/dfs/include/dfs_private.h
@@ -0,0 +1,21 @@
+#ifndef DFS_PRIVATE_H__
+#define DFS_PRIVATE_H__
+
+#include <dfs.h>
+
+// #define DBG_ENABLE
+#define DBG_SECTION_NAME	"[ DFS]"
+#define DBG_COLOR
+#define DBG_LEVEL			DBG_LOG
+#include <rtdbg.h>
+
+#define NO_WORKING_DIR  "system does not support working directory\n"
+
+/* extern variable */
+extern const struct dfs_filesystem_ops *filesystem_operation_table[];
+extern struct dfs_filesystem filesystem_table[];
+extern const struct dfs_mount_tbl mount_table[];
+
+extern char working_directory[];
+
+#endif
diff --git a/components/dfs/src/dfs.c b/components/dfs/src/dfs.c
index f5176b7477..e5a8aa549d 100644
--- a/components/dfs/src/dfs.c
+++ b/components/dfs/src/dfs.c
@@ -25,9 +25,10 @@
 #include <dfs.h>
 #include <dfs_fs.h>
 #include <dfs_file.h>
+#include "dfs_private.h"
 
 /* Global variables */
-const struct dfs_filesystem_operation *filesystem_operation_table[DFS_FILESYSTEM_TYPES_MAX];
+const struct dfs_filesystem_ops *filesystem_operation_table[DFS_FILESYSTEM_TYPES_MAX];
 struct dfs_filesystem filesystem_table[DFS_FILESYSTEMS_MAX];
 
 /* device filesystem lock */
@@ -37,11 +38,7 @@ static struct rt_mutex fslock;
 char working_directory[DFS_PATH_MAX] = {"/"};
 #endif
 
-#ifdef DFS_USING_STDIO
-struct dfs_fd fd_table[3 + DFS_FD_MAX];
-#else
 struct dfs_fd fd_table[DFS_FD_MAX];
-#endif
 
 /**
  * @addtogroup DFS
@@ -55,23 +52,35 @@ struct dfs_fd fd_table[DFS_FD_MAX];
 int dfs_init(void)
 {
     /* clear filesystem operations table */
-    rt_memset((void *)filesystem_operation_table, 0, sizeof(filesystem_operation_table));
+    memset((void *)filesystem_operation_table, 0, sizeof(filesystem_operation_table));
     /* clear filesystem table */
-    rt_memset(filesystem_table, 0, sizeof(filesystem_table));
+    memset(filesystem_table, 0, sizeof(filesystem_table));
     /* clean fd table */
-    rt_memset(fd_table, 0, sizeof(fd_table));
+    memset(fd_table, 0, sizeof(fd_table));
 
     /* create device filesystem lock */
     rt_mutex_init(&fslock, "fslock", RT_IPC_FLAG_FIFO);
 
 #ifdef DFS_USING_WORKDIR
     /* set current working directory */
-    rt_memset(working_directory, 0, sizeof(working_directory));
+    memset(working_directory, 0, sizeof(working_directory));
     working_directory[0] = '/';
 #endif
-	return 0;
+
+#ifdef RT_USING_DFS_DEVFS
+    {
+        extern int devfs_init(void);
+
+        /* if enable devfs, initialize and mount it as soon as possible */
+        devfs_init();
+
+        dfs_mount(NULL, "/dev", "devfs", 0, 0);
+    }
+#endif
+
+    return 0;
 }
-INIT_COMPONENT_EXPORT(dfs_init);
+INIT_PREV_EXPORT(dfs_init);
 
 /**
  * this function will lock device file system.
@@ -114,18 +123,10 @@ int fd_new(void)
     dfs_lock();
 
     /* find an empty fd entry */
-#ifdef DFS_USING_STDIO
-    for (idx = 3; idx < DFS_FD_MAX + 3 && fd_table[idx].ref_count > 0; idx++);
-#else
     for (idx = 0; idx < DFS_FD_MAX && fd_table[idx].ref_count > 0; idx++);
-#endif
 
     /* can't find an empty fd entry */
-#ifdef DFS_USING_STDIO
-    if (idx == DFS_FD_MAX + 3)
-#else
     if (idx == DFS_FD_MAX)
-#endif
     {
         idx = -1;
         goto __result;
@@ -137,7 +138,7 @@ int fd_new(void)
 
 __result:
     dfs_unlock();
-    return idx;
+    return idx + DFS_FD_OFFSET;
 }
 
 /**
@@ -153,13 +154,9 @@ struct dfs_fd *fd_get(int fd)
 {
     struct dfs_fd *d;
 
-#ifdef DFS_USING_STDIO
-    if (fd < 3 || fd >= DFS_FD_MAX + 3)
-        return RT_NULL;
-#else
+    fd = fd - DFS_FD_OFFSET;
     if (fd < 0 || fd >= DFS_FD_MAX)
-        return RT_NULL;
-#endif
+        return NULL;
 
     dfs_lock();
     d = &fd_table[fd];
@@ -168,7 +165,7 @@ struct dfs_fd *fd_get(int fd)
     if (d->magic != DFS_FD_MAGIC)
     {
         dfs_unlock();
-        return RT_NULL;
+        return NULL;
     }
 
     /* increase the reference count */
@@ -185,7 +182,7 @@ struct dfs_fd *fd_get(int fd)
  */
 void fd_put(struct dfs_fd *fd)
 {
-    RT_ASSERT(fd != RT_NULL);
+    RT_ASSERT(fd != NULL);
 
     dfs_lock();
     fd->ref_count --;
@@ -193,10 +190,10 @@ void fd_put(struct dfs_fd *fd)
     /* clear this fd entry */
     if (fd->ref_count == 0)
     {
-        rt_memset(fd, 0, sizeof(struct dfs_fd));
+        memset(fd, 0, sizeof(struct dfs_fd));
     }
     dfs_unlock();
-};
+}
 
 /**
  * @ingroup Fd
@@ -214,15 +211,15 @@ int fd_is_open(const char *pathname)
     struct dfs_filesystem *fs;
     struct dfs_fd *fd;
 
-    fullpath = dfs_normalize_path(RT_NULL, pathname);
-    if (fullpath != RT_NULL)
+    fullpath = dfs_normalize_path(NULL, pathname);
+    if (fullpath != NULL)
     {
         char *mountpath;
         fs = dfs_filesystem_lookup(fullpath);
-        if (fs == RT_NULL)
+        if (fs == NULL)
         {
             /* can't find mounted file system */
-            rt_free(fullpath);
+            free(fullpath);
 
             return -1;
         }
@@ -234,17 +231,14 @@ int fd_is_open(const char *pathname)
             mountpath = fullpath + strlen(fs->path);
 
         dfs_lock();
-#ifdef DFS_USING_STDIO
-        for (index = 3; index < DFS_FD_MAX+3; index++)
-#else
+
         for (index = 0; index < DFS_FD_MAX; index++)
-#endif
         {
             fd = &(fd_table[index]);
-            if (fd->fs == RT_NULL)
+            if (fd->fops == NULL)
                 continue;
 
-            if (fd->fs == fs && strcmp(fd->path, mountpath) == 0)
+            if (fd->fops == fs->ops->fops && strcmp(fd->path, mountpath) == 0)
             {
                 /* found file in file descriptor table */
                 rt_free(fullpath);
@@ -274,7 +268,7 @@ const char *dfs_subdir(const char *directory, const char *filename)
     const char *dir;
 
     if (strlen(directory) == strlen(filename)) /* it's a same path */
-        return RT_NULL;
+        return NULL;
 
     dir = filename + strlen(directory);
     if ((*dir != '/') && (dir != filename))
@@ -301,17 +295,17 @@ char *dfs_normalize_path(const char *directory, const char *filename)
     char *dst0, *dst, *src;
 
     /* check parameters */
-    RT_ASSERT(filename != RT_NULL);
+    RT_ASSERT(filename != NULL);
 
 #ifdef DFS_USING_WORKDIR
-    if (directory == RT_NULL) /* shall use working directory */
+    if (directory == NULL) /* shall use working directory */
         directory = &working_directory[0];
 #else
-    if ((directory == RT_NULL) && (filename[0] != '/'))
+    if ((directory == NULL) && (filename[0] != '/'))
     {
         rt_kprintf(NO_WORKING_DIR);
 
-        return RT_NULL;
+        return NULL;
     }
 #endif
 
@@ -319,8 +313,8 @@ char *dfs_normalize_path(const char *directory, const char *filename)
     {
         fullpath = rt_malloc(strlen(directory) + strlen(filename) + 2);
 
-        if (fullpath == RT_NULL)
-            return RT_NULL;
+        if (fullpath == NULL)
+            return NULL;
 
         /* join path and file name */
         rt_snprintf(fullpath, strlen(directory) + strlen(filename) + 2,
@@ -330,8 +324,8 @@ char *dfs_normalize_path(const char *directory, const char *filename)
     {
         fullpath = rt_strdup(filename); /* copy string */
 
-        if (fullpath == RT_NULL)
-            return RT_NULL;
+        if (fullpath == NULL)
+            return NULL;
     }
 
     src = fullpath;
@@ -396,7 +390,7 @@ up_one:
         if (dst < dst0)
         {
             rt_free(fullpath);
-            return RT_NULL;
+            return NULL;
         }
         while (dst0 < dst && dst[-1] != '/')
             dst --;
@@ -413,5 +407,37 @@ up_one:
 }
 RTM_EXPORT(dfs_normalize_path);
 
+#include <finsh.h>
+int list_fd(void)
+{
+    int index;
+
+    rt_enter_critical();
+
+    for (index = 0; index < DFS_FD_MAX; index ++)
+    {
+        struct dfs_fd *fd = &(fd_table[index]);
+
+        if (fd->fops)
+        {
+            rt_kprintf("--fd: %d--", index);
+            if (fd->type == FT_DIRECTORY) rt_kprintf("[dir]\n");
+            if (fd->type == FT_REGULAR)   rt_kprintf("[file]\n");
+            if (fd->type == FT_SOCKET)    rt_kprintf("[socket]\n");
+            if (fd->type == FT_USER)      rt_kprintf("[user]\n");
+            rt_kprintf("refcount=%d\n", fd->ref_count);
+            rt_kprintf("magic=0x%04x\n", fd->magic);
+            if (fd->path)
+            {
+                rt_kprintf("path: %s\n", fd->path);
+            }
+        }
+    }
+    rt_exit_critical();
+
+    return 0;
+}
+MSH_CMD_EXPORT(list_fd, list file descriptor);
+
 /*@}*/
 
diff --git a/components/dfs/src/dfs_file.c b/components/dfs/src/dfs_file.c
index 27ab52f64c..8ebccac2a5 100644
--- a/components/dfs/src/dfs_file.c
+++ b/components/dfs/src/dfs_file.c
@@ -26,6 +26,7 @@
 
 #include <dfs.h>
 #include <dfs_file.h>
+#include <dfs_private.h>
 
 /**
  * @addtogroup FileApi
@@ -49,44 +50,53 @@ int dfs_file_open(struct dfs_fd *fd, const char *path, int flags)
     int result;
 
     /* parameter check */
-    if (fd == RT_NULL)
-        return -DFS_STATUS_EINVAL;
+    if (fd == NULL)
+        return -EINVAL;
 
     /* make sure we have an absolute path */
-    fullpath = dfs_normalize_path(RT_NULL, path);
-    if (fullpath == RT_NULL)
+    fullpath = dfs_normalize_path(NULL, path);
+    if (fullpath == NULL)
     {
-        return -1;
+        return -ENOMEM;
     }
 
-    dfs_log(DFS_DEBUG_INFO, ("open file:%s", fullpath));
+    dbg_log(DBG_LOG, "open file:%s\n", fullpath);
+
+    /* Check whether file is already open */
+    if (fd_is_open(fullpath) == 0)
+    {
+        rt_free(fullpath); /* release path */
+
+        return -EBUSY;
+    }
 
     /* find filesystem */
     fs = dfs_filesystem_lookup(fullpath);
-    if (fs == RT_NULL)
+    if (fs == NULL)
     {
         rt_free(fullpath); /* release path */
 
-        return -DFS_STATUS_ENOENT;
+        return -ENOENT;
     }
 
-    dfs_log(DFS_DEBUG_INFO, ("open in filesystem:%s", fs->ops->name));
-    fd->fs = fs;
+    dbg_log(DBG_LOG, "open in filesystem:%s\n", fs->ops->name);
+    fd->fops  = fs->ops->fops; /* set file ops */
 
     /* initialize the fd item */
     fd->type  = FT_REGULAR;
     fd->flags = flags;
     fd->size  = 0;
     fd->pos   = 0;
+    fd->data  = fs;
 
     if (!(fs->ops->flags & DFS_FS_FLAG_FULLPATH))
     {
-        if (dfs_subdir(fs->path, fullpath) == RT_NULL)
+        if (dfs_subdir(fs->path, fullpath) == NULL)
             fd->path = rt_strdup("/");
         else
             fd->path = rt_strdup(dfs_subdir(fs->path, fullpath));
         rt_free(fullpath);
-        dfs_log(DFS_DEBUG_INFO, ("Actual file path: %s\n", fd->path));
+        dbg_log(DBG_LOG, "Actual file path: %s\n", fd->path);
     }
     else
     {
@@ -94,34 +104,34 @@ int dfs_file_open(struct dfs_fd *fd, const char *path, int flags)
     }
 
     /* specific file system open routine */
-    if (fs->ops->open == RT_NULL)
+    if (fd->fops->open == NULL)
     {
         /* clear fd */
         rt_free(fd->path);
-        fd->path = RT_NULL;
+        fd->path = NULL;
 
-        return -DFS_STATUS_ENOSYS;
+        return -ENOSYS;
     }
 
-    if ((result = fs->ops->open(fd)) < 0)
+    if ((result = fd->fops->open(fd)) < 0)
     {
         /* clear fd */
         rt_free(fd->path);
-        fd->path = RT_NULL;
+        fd->path = NULL;
 
-        dfs_log(DFS_DEBUG_INFO, ("open failed"));
+        dbg_log(DBG_ERROR, "open failed\n");
 
         return result;
     }
 
     fd->flags |= DFS_F_OPEN;
-    if (flags & DFS_O_DIRECTORY)
+    if (flags & O_DIRECTORY)
     {
         fd->type = FT_DIRECTORY;
         fd->flags |= DFS_F_DIRECTORY;
     }
 
-    dfs_log(DFS_DEBUG_INFO, ("open successful"));
+    dbg_log(DBG_INFO, "open successful\n");
     return 0;
 }
 
@@ -136,18 +146,18 @@ int dfs_file_close(struct dfs_fd *fd)
 {
     int result = 0;
 
-    if (fd == RT_NULL)
-        return -DFS_STATUS_ENXIO;
+    if (fd == NULL)
+        return -ENXIO;
 
-    if (fd != RT_NULL && fd->fs->ops->close != RT_NULL)
-        result = fd->fs->ops->close(fd);
+    if (fd->fops->close != NULL)
+        result = fd->fops->close(fd);
 
     /* close fd error, return */
     if (result < 0)
         return result;
 
     rt_free(fd->path);
-    fd->path = RT_NULL;
+    fd->path = NULL;
 
     return result;
 }
@@ -163,16 +173,13 @@ int dfs_file_close(struct dfs_fd *fd)
  */
 int dfs_file_ioctl(struct dfs_fd *fd, int cmd, void *args)
 {
-    struct dfs_filesystem *fs;
-
-    if (fd == RT_NULL || fd->type != FT_REGULAR)
-        return -DFS_STATUS_EINVAL;
+    if (fd == NULL || fd->type != FT_REGULAR)
+        return -EINVAL;
 
-    fs = fd->fs;
-    if (fs->ops->ioctl != RT_NULL)
-        return fs->ops->ioctl(fd, cmd, args);
+    if (fd->fops->ioctl != NULL)
+        return fd->fops->ioctl(fd, cmd, args);
 
-    return -DFS_STATUS_ENOSYS;
+    return -ENOSYS;
 }
 
 /**
@@ -185,19 +192,17 @@ int dfs_file_ioctl(struct dfs_fd *fd, int cmd, void *args)
  *
  * @return the actual read data bytes or 0 on end of file or failed.
  */
-int dfs_file_read(struct dfs_fd *fd, void *buf, rt_size_t len)
+int dfs_file_read(struct dfs_fd *fd, void *buf, size_t len)
 {
-    struct dfs_filesystem *fs;
     int result = 0;
 
-    if (fd == RT_NULL)
-        return -DFS_STATUS_EINVAL;
+    if (fd == NULL)
+        return -EINVAL;
 
-    fs = (struct dfs_filesystem *)fd->fs;
-    if (fs->ops->read == RT_NULL)
-        return -DFS_STATUS_ENOSYS;
+    if (fd->fops->read == NULL)
+        return -ENOSYS;
 
-    if ((result = fs->ops->read(fd, buf, len)) < 0)
+    if ((result = fd->fops->read(fd, buf, len)) < 0)
         fd->flags |= DFS_F_EOF;
 
     return result;
@@ -212,19 +217,16 @@ int dfs_file_read(struct dfs_fd *fd, void *buf, rt_size_t len)
  *
  * @return the read dirent, others on failed.
  */
-int dfs_file_getdents(struct dfs_fd *fd, struct dirent *dirp, rt_size_t nbytes)
+int dfs_file_getdents(struct dfs_fd *fd, struct dirent *dirp, size_t nbytes)
 {
-    struct dfs_filesystem *fs;
-
     /* parameter check */
-    if (fd == RT_NULL || fd->type != FT_DIRECTORY)
-        return -DFS_STATUS_EINVAL;
+    if (fd == NULL || fd->type != FT_DIRECTORY)
+        return -EINVAL;
 
-    fs = (struct dfs_filesystem *)fd->fs;
-    if (fs->ops->getdents != RT_NULL)
-        return fs->ops->getdents(fd, dirp, nbytes);
+    if (fd->fops->getdents != NULL)
+        return fd->fops->getdents(fd, dirp, nbytes);
 
-    return -DFS_STATUS_ENOSYS;
+    return -ENOSYS;
 }
 
 /**
@@ -241,31 +243,31 @@ int dfs_file_unlink(const char *path)
     struct dfs_filesystem *fs;
 
     /* Make sure we have an absolute path */
-    fullpath = dfs_normalize_path(RT_NULL, path);
-    if (fullpath == RT_NULL)
+    fullpath = dfs_normalize_path(NULL, path);
+    if (fullpath == NULL)
     {
-        return -DFS_STATUS_EINVAL;
+        return -EINVAL;
     }
 
     /* get filesystem */
-    if ((fs = dfs_filesystem_lookup(fullpath)) == RT_NULL)
+    if ((fs = dfs_filesystem_lookup(fullpath)) == NULL)
     {
-        result = -DFS_STATUS_ENOENT;
+        result = -ENOENT;
         goto __exit;
     }
 
     /* Check whether file is already open */
     if (fd_is_open(fullpath) == 0)
     {
-        result = -DFS_STATUS_EBUSY;
+        result = -EBUSY;
         goto __exit;
     }
 
-    if (fs->ops->unlink != RT_NULL)
+    if (fs->ops->unlink != NULL)
     {
         if (!(fs->ops->flags & DFS_FS_FLAG_FULLPATH))
         {
-            if (dfs_subdir(fs->path, fullpath) == RT_NULL)
+            if (dfs_subdir(fs->path, fullpath) == NULL)
                 result = fs->ops->unlink(fs, "/");
             else
                 result = fs->ops->unlink(fs, dfs_subdir(fs->path, fullpath));
@@ -273,7 +275,7 @@ int dfs_file_unlink(const char *path)
         else
             result = fs->ops->unlink(fs, fullpath);
     }
-    else result = -DFS_STATUS_ENOSYS;
+    else result = -ENOSYS;
 
 __exit:
     rt_free(fullpath);
@@ -289,18 +291,15 @@ __exit:
  *
  * @return the actual written data length.
  */
-int dfs_file_write(struct dfs_fd *fd, const void *buf, rt_size_t len)
+int dfs_file_write(struct dfs_fd *fd, const void *buf, size_t len)
 {
-    struct dfs_filesystem *fs;
-
-    if (fd == RT_NULL)
-        return -DFS_STATUS_EINVAL;
+    if (fd == NULL)
+        return -EINVAL;
 
-    fs = fd->fs;
-    if (fs->ops->write == RT_NULL)
-        return -DFS_STATUS_ENOSYS;
+    if (fd->fops->write == NULL)
+        return -ENOSYS;
 
-    return fs->ops->write(fd, buf, len);
+    return fd->fops->write(fd, buf, len);
 }
 
 /**
@@ -312,16 +311,13 @@ int dfs_file_write(struct dfs_fd *fd, const void *buf, rt_size_t len)
  */
 int dfs_file_flush(struct dfs_fd *fd)
 {
-    struct dfs_filesystem *fs;
-
-    if (fd == RT_NULL)
-        return -DFS_STATUS_EINVAL;
+    if (fd == NULL)
+        return -EINVAL;
 
-    fs = fd->fs;
-    if (fs->ops->flush == RT_NULL)
-        return -DFS_STATUS_ENOSYS;
+    if (fd->fops->flush == NULL)
+        return -ENOSYS;
 
-    return fs->ops->flush(fd);
+    return fd->fops->flush(fd);
 }
 
 /**
@@ -332,20 +328,17 @@ int dfs_file_flush(struct dfs_fd *fd)
  *
  * @return the current position after seek.
  */
-int dfs_file_lseek(struct dfs_fd *fd, rt_off_t offset)
+int dfs_file_lseek(struct dfs_fd *fd, off_t offset)
 {
     int result;
-    struct dfs_filesystem *fs = fd->fs;
 
-    if (fd == RT_NULL)
-        return -DFS_STATUS_EINVAL;
-    fs = fd->fs;
-    if (fs == RT_NULL)
-        return -DFS_STATUS_EINVAL;
-    if (fs->ops->lseek == RT_NULL)
-        return -DFS_STATUS_ENOSYS;
+    if (fd == NULL)
+        return -EINVAL;
 
-    result = fs->ops->lseek(fd, offset);
+    if (fd->fops->lseek == NULL)
+        return -ENOSYS;
+
+    result = fd->fops->lseek(fd, offset);
 
     /* update current position */
     if (result >= 0)
@@ -368,30 +361,30 @@ int dfs_file_stat(const char *path, struct stat *buf)
     char *fullpath;
     struct dfs_filesystem *fs;
 
-    fullpath = dfs_normalize_path(RT_NULL, path);
-    if (fullpath == RT_NULL)
+    fullpath = dfs_normalize_path(NULL, path);
+    if (fullpath == NULL)
     {
         return -1;
     }
 
-    if ((fs = dfs_filesystem_lookup(fullpath)) == RT_NULL)
+    if ((fs = dfs_filesystem_lookup(fullpath)) == NULL)
     {
-        dfs_log(DFS_DEBUG_ERROR,
-                ("can't find mounted filesystem on this path:%s", fullpath));
+        dbg_log(DBG_ERROR,
+                "can't find mounted filesystem on this path:%s\n", fullpath);
         rt_free(fullpath);
 
-        return -DFS_STATUS_ENOENT;
+        return -ENOENT;
     }
 
     if ((fullpath[0] == '/' && fullpath[1] == '\0') ||
-        (dfs_subdir(fs->path, fullpath) == RT_NULL))
+        (dfs_subdir(fs->path, fullpath) == NULL))
     {
         /* it's the root directory */
         buf->st_dev   = 0;
 
-        buf->st_mode  = DFS_S_IRUSR | DFS_S_IRGRP | DFS_S_IROTH |
-                        DFS_S_IWUSR | DFS_S_IWGRP | DFS_S_IWOTH;
-        buf->st_mode |= DFS_S_IFDIR | DFS_S_IXUSR | DFS_S_IXGRP | DFS_S_IXOTH;
+        buf->st_mode  = S_IRUSR | S_IRGRP | S_IROTH |
+                        S_IWUSR | S_IWGRP | S_IWOTH;
+        buf->st_mode |= S_IFDIR | S_IXUSR | S_IXGRP | S_IXOTH;
 
         buf->st_size    = 0;
         buf->st_mtime   = 0;
@@ -399,17 +392,17 @@ int dfs_file_stat(const char *path, struct stat *buf)
         /* release full path */
         rt_free(fullpath);
 
-        return DFS_STATUS_OK;
+        return RT_EOK;
     }
     else
     {
-        if (fs->ops->stat == RT_NULL)
+        if (fs->ops->stat == NULL)
         {
             rt_free(fullpath);
-            dfs_log(DFS_DEBUG_ERROR,
-                    ("the filesystem didn't implement this function"));
+            dbg_log(DBG_ERROR,
+                    "the filesystem didn't implement this function\n");
 
-            return -DFS_STATUS_ENOSYS;
+            return -ENOSYS;
         }
 
         /* get the real file path and get file stat */
@@ -438,21 +431,21 @@ int dfs_file_rename(const char *oldpath, const char *newpath)
     struct dfs_filesystem *oldfs, *newfs;
     char *oldfullpath, *newfullpath;
 
-    result = DFS_STATUS_OK;
-    newfullpath = RT_NULL;
-    oldfullpath = RT_NULL;
+    result = RT_EOK;
+    newfullpath = NULL;
+    oldfullpath = NULL;
 
-    oldfullpath = dfs_normalize_path(RT_NULL, oldpath);
-    if (oldfullpath == RT_NULL)
+    oldfullpath = dfs_normalize_path(NULL, oldpath);
+    if (oldfullpath == NULL)
     {
-        result = -DFS_STATUS_ENOENT;
+        result = -ENOENT;
         goto __exit;
     }
 
-    newfullpath = dfs_normalize_path(RT_NULL, newpath);
-    if (newfullpath == RT_NULL)
+    newfullpath = dfs_normalize_path(NULL, newpath);
+    if (newfullpath == NULL)
     {
-        result = -DFS_STATUS_ENOENT;
+        result = -ENOENT;
         goto __exit;
     }
 
@@ -461,9 +454,9 @@ int dfs_file_rename(const char *oldpath, const char *newpath)
 
     if (oldfs == newfs)
     {
-        if (oldfs->ops->rename == RT_NULL)
+        if (oldfs->ops->rename == NULL)
         {
-            result = -DFS_STATUS_ENOSYS;
+            result = -ENOSYS;
         }
         else
         {
@@ -478,7 +471,7 @@ int dfs_file_rename(const char *oldpath, const char *newpath)
     }
     else
     {
-        result = -DFS_STATUS_EXDEV;
+        result = -EXDEV;
     }
 
 __exit:
@@ -500,8 +493,8 @@ void ls(const char *pathname)
     int length;
     char *fullpath, *path;
 
-    fullpath = RT_NULL;
-    if (pathname == RT_NULL)
+    fullpath = NULL;
+    if (pathname == NULL)
     {
 #ifdef DFS_USING_WORKDIR
         /* open current working directory */
@@ -509,7 +502,7 @@ void ls(const char *pathname)
 #else
         path = rt_strdup("/");
 #endif
-        if (path == RT_NULL)
+        if (path == NULL)
             return ; /* out of memory */
     }
     else
@@ -518,26 +511,26 @@ void ls(const char *pathname)
     }
 
     /* list directory */
-    if (dfs_file_open(&fd, path, DFS_O_DIRECTORY) == 0)
+    if (dfs_file_open(&fd, path, O_DIRECTORY) == 0)
     {
         rt_kprintf("Directory %s:\n", path);
         do
         {
-            rt_memset(&dirent, 0, sizeof(struct dirent));
+            memset(&dirent, 0, sizeof(struct dirent));
             length = dfs_file_getdents(&fd, &dirent, sizeof(struct dirent));
             if (length > 0)
             {
-                rt_memset(&stat, 0, sizeof(struct stat));
+                memset(&stat, 0, sizeof(struct stat));
 
                 /* build full path for each file */
                 fullpath = dfs_normalize_path(path, dirent.d_name);
-                if (fullpath == RT_NULL)
+                if (fullpath == NULL)
                     break;
 
                 if (dfs_file_stat(fullpath, &stat) == 0)
                 {
                     rt_kprintf("%-20s", dirent.d_name);
-                    if ( DFS_S_ISDIR(stat.st_mode))
+                    if (S_ISDIR(stat.st_mode))
                     {
                         rt_kprintf("%-25s\n", "<DIR>");
                     }
@@ -558,7 +551,7 @@ void ls(const char *pathname)
     {
         rt_kprintf("No such directory\n");
     }
-    if (pathname == RT_NULL)
+    if (pathname == NULL)
         rt_free(path);
 }
 FINSH_FUNCTION_EXPORT(ls, list directory contents);
@@ -574,10 +567,10 @@ FINSH_FUNCTION_EXPORT(rm, remove files or directories);
 
 void cat(const char* filename)
 {
-    rt_uint32_t length;
+    uint32_t length;
     char buffer[81];
 
-    if (dfs_file_open(&fd, filename, DFS_O_RDONLY) < 0)
+    if (dfs_file_open(&fd, filename, O_RDONLY) < 0)
     {
         rt_kprintf("Open %s failed\n", filename);
 
@@ -586,7 +579,7 @@ void cat(const char* filename)
 
     do
     {
-        rt_memset(buffer, 0, sizeof(buffer));
+        memset(buffer, 0, sizeof(buffer));
         length = dfs_file_read(&fd, buffer, sizeof(buffer)-1 );
         if (length > 0)
         {
@@ -606,21 +599,21 @@ static void copyfile(const char *src, const char *dst)
     rt_int32_t read_bytes;
 
     block_ptr = rt_malloc(BUF_SZ);
-    if (block_ptr == RT_NULL)
+    if (block_ptr == NULL)
     {
         rt_kprintf("out of memory\n");
 
         return;
     }
 
-    if (dfs_file_open(&src_fd, src, DFS_O_RDONLY) < 0)
+    if (dfs_file_open(&src_fd, src, O_RDONLY) < 0)
     {
         rt_free(block_ptr);
         rt_kprintf("Read %s failed\n", src);
 
         return;
     }
-    if (dfs_file_open(&fd, dst, DFS_O_WRONLY | DFS_O_CREAT) < 0)
+    if (dfs_file_open(&fd, dst, O_WRONLY | O_CREAT) < 0)
     {
         rt_free(block_ptr);
         dfs_file_close(&src_fd);
@@ -659,7 +652,7 @@ static void copydir(const char * src, const char * dst)
     struct stat stat;
     int length;
     struct dfs_fd cpfd;
-    if (dfs_file_open(&cpfd, src, DFS_O_DIRECTORY) < 0)
+    if (dfs_file_open(&cpfd, src, O_DIRECTORY) < 0)
     {
         rt_kprintf("open %s failed\n", src);
         return ;
@@ -667,37 +660,38 @@ static void copydir(const char * src, const char * dst)
 
     do
     {
-        rt_memset(&dirent, 0, sizeof(struct dirent));
+        memset(&dirent, 0, sizeof(struct dirent));
+
         length = dfs_file_getdents(&cpfd, &dirent, sizeof(struct dirent));
         if (length > 0)
         {
-            char * src_entry_full = RT_NULL;
-            char * dst_entry_full = RT_NULL;
+            char * src_entry_full = NULL;
+            char * dst_entry_full = NULL;
 
             if (strcmp(dirent.d_name, "..") == 0 || strcmp(dirent.d_name, ".") == 0)
                 continue;
 
             /* build full path for each file */
-            if ((src_entry_full = dfs_normalize_path(src, dirent.d_name)) == RT_NULL)
+            if ((src_entry_full = dfs_normalize_path(src, dirent.d_name)) == NULL)
             {
                 rt_kprintf("out of memory!\n");
                 break;
             }
-            if ((dst_entry_full = dfs_normalize_path(dst, dirent.d_name)) == RT_NULL)
+            if ((dst_entry_full = dfs_normalize_path(dst, dirent.d_name)) == NULL)
             {
                 rt_kprintf("out of memory!\n");
                 rt_free(src_entry_full);
                 break;
             }
 
-            rt_memset(&stat, 0, sizeof(struct stat));
+            memset(&stat, 0, sizeof(struct stat));
             if (dfs_file_stat(src_entry_full, &stat) != 0)
             {
                 rt_kprintf("open file: %s failed\n", dirent.d_name);
                 continue;
             }
 
-            if (DFS_S_ISDIR(stat.st_mode))
+            if (S_ISDIR(stat.st_mode))
             {
                 mkdir(dst_entry_full, 0);
                 copydir(src_entry_full, dst_entry_full);
@@ -717,7 +711,7 @@ static void copydir(const char * src, const char * dst)
 static const char *_get_path_lastname(const char *path)
 {
     char * ptr;
-    if ((ptr = strrchr(path, '/')) == RT_NULL)
+    if ((ptr = strrchr(path, '/')) == NULL)
         return path;
 
     /* skip the '/' then return */
@@ -736,7 +730,7 @@ void copy(const char *src, const char *dst)
 #define FLAG_DST_NON_EXSIT 0x00
 
     struct stat stat;
-    rt_uint32_t flag = 0;
+    uint32_t flag = 0;
 
     /* check the staus of src and dst */
     if (dfs_file_stat(src, &stat) < 0)
@@ -744,7 +738,7 @@ void copy(const char *src, const char *dst)
         rt_kprintf("copy failed, bad %s\n", src);
         return;
     }
-    if (DFS_S_ISDIR(stat.st_mode))
+    if (S_ISDIR(stat.st_mode))
         flag |= FLAG_SRC_IS_DIR;
     else
         flag |= FLAG_SRC_IS_FILE;
@@ -755,7 +749,7 @@ void copy(const char *src, const char *dst)
     }
     else
     {
-        if (DFS_S_ISDIR(stat.st_mode))
+        if (S_ISDIR(stat.st_mode))
             flag |= FLAG_DST_IS_DIR;
         else
             flag |= FLAG_DST_IS_FILE;
diff --git a/components/dfs/src/dfs_fs.c b/components/dfs/src/dfs_fs.c
index bdd9560d56..ee3862ce3c 100644
--- a/components/dfs/src/dfs_fs.c
+++ b/components/dfs/src/dfs_fs.c
@@ -26,6 +26,7 @@
 
 #include <dfs_fs.h>
 #include <dfs_file.h>
+#include "dfs_private.h"
 
 /**
  * @addtogroup FsApi
@@ -37,13 +38,13 @@
  *
  * @param ops the file system instance to be registered.
  *
- * @return RT_EOK on successful, -RT_ERROR on failed.
+ * @return 0 on successful, -1 on failed.
  */
-int dfs_register(const struct dfs_filesystem_operation *ops)
+int dfs_register(const struct dfs_filesystem_ops *ops)
 {
     int ret = RT_EOK;
-    const struct dfs_filesystem_operation **empty = RT_NULL;
-    const struct dfs_filesystem_operation **iter;
+    const struct dfs_filesystem_ops **empty = NULL;
+    const struct dfs_filesystem_ops **iter;
 
     /* lock filesystem */
     dfs_lock();
@@ -52,18 +53,26 @@ int dfs_register(const struct dfs_filesystem_operation *ops)
            iter < &filesystem_operation_table[DFS_FILESYSTEM_TYPES_MAX]; iter ++)
     {
         /* find out an empty filesystem type entry */
-        if (*iter == RT_NULL)
-            (empty == RT_NULL) ? (empty = iter) : 0;
+        if (*iter == NULL)
+            (empty == NULL) ? (empty = iter) : 0;
         else if (strcmp((*iter)->name, ops->name) == 0)
         {
+            rt_set_errno(-EEXIST);
             ret = -1;
             break;
         }
     }
 
     /* save the filesystem's operations */
-    if ((ret == RT_EOK) && (empty != RT_NULL))
+    if (empty == NULL)
+    {
+        rt_set_errno(-ENOSPC);
+        ret = -1;
+    }
+    else if (ret == RT_EOK)
+    {
         *empty = ops;
+    }
 
     dfs_unlock();
     return ret;
@@ -80,8 +89,8 @@ int dfs_register(const struct dfs_filesystem_operation *ops)
 struct dfs_filesystem *dfs_filesystem_lookup(const char *path)
 {
     struct dfs_filesystem *iter;
-    struct dfs_filesystem *fs = RT_NULL;
-    rt_uint32_t fspath, prefixlen;
+    struct dfs_filesystem *fs = NULL;
+    uint32_t fspath, prefixlen;
 
     prefixlen = 0;
 
@@ -94,7 +103,7 @@ struct dfs_filesystem *dfs_filesystem_lookup(const char *path)
     for (iter = &filesystem_table[0];
             iter < &filesystem_table[DFS_FILESYSTEMS_MAX]; iter++)
     {
-        if ((iter->path == RT_NULL) || (iter->ops == RT_NULL))
+        if ((iter->path == NULL) || (iter->ops == NULL))
             continue;
 
         fspath = strlen(iter->path);
@@ -116,34 +125,34 @@ struct dfs_filesystem *dfs_filesystem_lookup(const char *path)
 }
 
 /**
- * this function will return the mounted path for specified device. 
+ * this function will return the mounted path for specified device.
  *
  * @param device the device object which is mounted.
  *
- * @return the mounted path or RT_NULL if none device mounted. 
+ * @return the mounted path or NULL if none device mounted.
  */
 const char* dfs_filesystem_get_mounted_path(struct rt_device* device)
 {
-	const char* path = RT_NULL;
+    const char* path = NULL;
     struct dfs_filesystem *iter;
 
     dfs_lock();
     for (iter = &filesystem_table[0];
             iter < &filesystem_table[DFS_FILESYSTEMS_MAX]; iter++)
     {
-		/* fint the mounted device */
-        if (iter->ops == RT_NULL) continue;
-		else if (iter->dev_id == device) 
-		{
-			path = iter->path;
-			break;
-		}
+        /* fint the mounted device */
+        if (iter->ops == NULL) continue;
+        else if (iter->dev_id == device)
+        {
+            path = iter->path;
+            break;
+        }
     }
 
     /* release filesystem_table lock */
     dfs_unlock();
 
-	return path;
+    return path;
 }
 
 /**
@@ -155,29 +164,29 @@ const char* dfs_filesystem_get_mounted_path(struct rt_device* device)
  *
  * @return RT_EOK on successful or -RT_ERROR on failed.
  */
-rt_err_t dfs_filesystem_get_partition(struct dfs_partition *part,
-                                      rt_uint8_t           *buf,
-                                      rt_uint32_t           pindex)
+int dfs_filesystem_get_partition(struct dfs_partition *part,
+                                      uint8_t         *buf,
+                                      uint32_t        pindex)
 {
 #define DPT_ADDRESS     0x1be       /* device partition offset in Boot Sector */
 #define DPT_ITEM_SIZE   16          /* partition item size */
 
-    rt_uint8_t *dpt;
-    rt_uint8_t type;
+    uint8_t *dpt;
+    uint8_t type;
 
-    RT_ASSERT(part != RT_NULL);
-    RT_ASSERT(buf != RT_NULL);
+    RT_ASSERT(part != NULL);
+    RT_ASSERT(buf != NULL);
 
     dpt = buf + DPT_ADDRESS + pindex * DPT_ITEM_SIZE;
 
     /* check if it is a valid partition table */
     if ((*dpt != 0x80) && (*dpt != 0x00))
-        return -RT_ERROR;
+        return -EIO;
 
     /* get partition type */
     type = *(dpt+4);
     if (type == 0)
-        return -RT_ERROR;
+        return -EIO;
 
     /* set partition information
      *    size is the number of 512-Byte */
@@ -219,22 +228,22 @@ int dfs_mount(const char   *device_name,
               unsigned long rwflag,
               const void   *data)
 {
-    const struct dfs_filesystem_operation **ops;
+    const struct dfs_filesystem_ops **ops;
     struct dfs_filesystem *iter;
-    struct dfs_filesystem *fs = RT_NULL;
-    char *fullpath = RT_NULL;
+    struct dfs_filesystem *fs = NULL;
+    char *fullpath = NULL;
     rt_device_t dev_id;
 
     /* open specific device */
-    if (device_name == RT_NULL)
+    if (device_name == NULL)
     {
         /* which is a non-device filesystem mount */
         dev_id = NULL;
     }
-    else if ((dev_id = rt_device_find(device_name)) == RT_NULL)
+    else if ((dev_id = rt_device_find(device_name)) == NULL)
     {
         /* no this device */
-        rt_set_errno(-DFS_STATUS_ENODEV);
+        rt_set_errno(-ENODEV);
         return -1;
     }
 
@@ -243,7 +252,7 @@ int dfs_mount(const char   *device_name,
 
     for (ops = &filesystem_operation_table[0];
            ops < &filesystem_operation_table[DFS_FILESYSTEM_TYPES_MAX]; ops++)
-        if ((ops != RT_NULL) && (strcmp((*ops)->name, filesystemtype) == 0))
+        if ((ops != NULL) && (strcmp((*ops)->name, filesystemtype) == 0))
             break;
 
     dfs_unlock();
@@ -251,22 +260,22 @@ int dfs_mount(const char   *device_name,
     if (ops == &filesystem_operation_table[DFS_FILESYSTEM_TYPES_MAX])
     {
         /* can't find filesystem */
-        rt_set_errno(-DFS_STATUS_ENODEV);
+        rt_set_errno(-ENODEV);
         return -1;
     }
 
     /* check if there is mount implementation */
     if ((*ops == NULL) || ((*ops)->mount == NULL))
     {
-        rt_set_errno(-DFS_STATUS_ENOSYS);
+        rt_set_errno(-ENOSYS);
         return -1;
     }
 
     /* make full path for special file */
-    fullpath = dfs_normalize_path(RT_NULL, path);
-    if (fullpath == RT_NULL) /* not an abstract path */
+    fullpath = dfs_normalize_path(NULL, path);
+    if (fullpath == NULL) /* not an abstract path */
     {
-        rt_set_errno(-DFS_STATUS_ENOTDIR);
+        rt_set_errno(-ENOTDIR);
         return -1;
     }
 
@@ -275,10 +284,10 @@ int dfs_mount(const char   *device_name,
     {
         struct dfs_fd fd;
 
-        if (dfs_file_open(&fd, fullpath, DFS_O_RDONLY | DFS_O_DIRECTORY) < 0)
+        if (dfs_file_open(&fd, fullpath, O_RDONLY | O_DIRECTORY) < 0)
         {
             rt_free(fullpath);
-            rt_set_errno(-DFS_STATUS_ENOTDIR);
+            rt_set_errno(-ENOTDIR);
 
             return -1;
         }
@@ -293,19 +302,19 @@ int dfs_mount(const char   *device_name,
             iter < &filesystem_table[DFS_FILESYSTEMS_MAX]; iter++)
     {
         /* check if it is an empty filesystem table entry? if it is, save fs */
-        if (iter->ops == RT_NULL)
-            (fs == RT_NULL) ? (fs = iter) : 0;
+        if (iter->ops == NULL)
+            (fs == NULL) ? (fs = iter) : 0;
         /* check if the PATH is mounted */
         else if (strcmp(iter->path, path) == 0)
         {
-            rt_set_errno(-DFS_STATUS_EINVAL);
+            rt_set_errno(-EINVAL);
             goto err1;
         }
     }
 
-    if ((fs == RT_NULL) && (iter == &filesystem_table[DFS_FILESYSTEMS_MAX]))
+    if ((fs == NULL) && (iter == &filesystem_table[DFS_FILESYSTEMS_MAX]))
     {
-        rt_set_errno(-DFS_STATUS_ENOSPC);
+        rt_set_errno(-ENOSPC);
         goto err1;
     }
 
@@ -317,14 +326,15 @@ int dfs_mount(const char   *device_name,
     dfs_unlock();
 
     /* open device, but do not check the status of device */
-    if (dev_id != RT_NULL)
+    if (dev_id != NULL)
     {
         if (rt_device_open(fs->dev_id,
                            RT_DEVICE_OFLAG_RDWR) != RT_EOK)
         {
             /* The underlaying device has error, clear the entry. */
             dfs_lock();
-            rt_memset(fs, 0, sizeof(struct dfs_filesystem));
+            memset(fs, 0, sizeof(struct dfs_filesystem));
+
             goto err1;
         }
     }
@@ -333,13 +343,14 @@ int dfs_mount(const char   *device_name,
     if ((*ops)->mount(fs, rwflag, data) < 0)
     {
         /* close device */
-        if (dev_id != RT_NULL)
+        if (dev_id != NULL)
             rt_device_close(fs->dev_id);
 
         /* mount failed */
         dfs_lock();
         /* clear filesystem table entry */
-        rt_memset(fs, 0, sizeof(struct dfs_filesystem));
+        memset(fs, 0, sizeof(struct dfs_filesystem));
+
         goto err1;
     }
 
@@ -363,12 +374,12 @@ int dfs_unmount(const char *specialfile)
 {
     char *fullpath;
     struct dfs_filesystem *iter;
-    struct dfs_filesystem *fs = RT_NULL;
+    struct dfs_filesystem *fs = NULL;
 
-    fullpath = dfs_normalize_path(RT_NULL, specialfile);
-    if (fullpath == RT_NULL)
+    fullpath = dfs_normalize_path(NULL, specialfile);
+    if (fullpath == NULL)
     {
-        rt_set_errno(-DFS_STATUS_ENOTDIR);
+        rt_set_errno(-ENOTDIR);
 
         return -1;
     }
@@ -387,22 +398,22 @@ int dfs_unmount(const char *specialfile)
         }
     }
 
-    if (fs == RT_NULL ||
-        fs->ops->unmount == RT_NULL ||
+    if (fs == NULL ||
+        fs->ops->unmount == NULL ||
         fs->ops->unmount(fs) < 0)
     {
         goto err1;
     }
 
     /* close device, but do not check the status of device */
-    if (fs->dev_id != RT_NULL)
+    if (fs->dev_id != NULL)
         rt_device_close(fs->dev_id);
 
-    if (fs->path != RT_NULL)
+    if (fs->path != NULL)
         rt_free(fs->path);
 
     /* clear this filesystem table entry */
-    rt_memset(fs, 0, sizeof(struct dfs_filesystem));
+    memset(fs, 0, sizeof(struct dfs_filesystem));
 
     dfs_unlock();
     rt_free(fullpath);
@@ -427,15 +438,15 @@ err1:
 int dfs_mkfs(const char *fs_name, const char *device_name)
 {
     int index;
-    rt_device_t dev_id = RT_NULL;
+    rt_device_t dev_id = NULL;
 
     /* check device name, and it should not be NULL */
-    if (device_name != RT_NULL)
+    if (device_name != NULL)
         dev_id = rt_device_find(device_name);
 
-    if (dev_id == RT_NULL)
+    if (dev_id == NULL)
     {
-        rt_set_errno(-DFS_STATUS_ENODEV);
+        rt_set_errno(-ENODEV);
         return -1;
     }
 
@@ -444,7 +455,7 @@ int dfs_mkfs(const char *fs_name, const char *device_name)
     /* find the file system operations */
     for (index = 0; index < DFS_FILESYSTEM_TYPES_MAX; index ++)
     {
-        if (filesystem_operation_table[index] != RT_NULL &&
+        if (filesystem_operation_table[index] != NULL &&
             strcmp(filesystem_operation_table[index]->name, fs_name) == 0)
             break;
     }
@@ -453,10 +464,10 @@ int dfs_mkfs(const char *fs_name, const char *device_name)
     if (index < DFS_FILESYSTEM_TYPES_MAX)
     {
         /* find file system operation */
-        const struct dfs_filesystem_operation *ops = filesystem_operation_table[index];
-        if (ops->mkfs == RT_NULL)
+        const struct dfs_filesystem_ops *ops = filesystem_operation_table[index];
+        if (ops->mkfs == NULL)
         {
-            rt_set_errno(-DFS_STATUS_ENOSYS);
+            rt_set_errno(-ENOSYS);
             return -1;
         }
 
@@ -480,9 +491,9 @@ int dfs_statfs(const char *path, struct statfs *buffer)
     struct dfs_filesystem *fs;
 
     fs = dfs_filesystem_lookup(path);
-    if (fs != RT_NULL)
+    if (fs != NULL)
     {
-        if (fs->ops->statfs != RT_NULL)
+        if (fs->ops->statfs != NULL)
             return fs->ops->statfs(fs, buffer);
     }
 
@@ -492,26 +503,26 @@ int dfs_statfs(const char *path, struct statfs *buffer)
 #ifdef RT_USING_DFS_MNTTABLE
 int dfs_mount_table(void)
 {
-	int index = 0;
+    int index = 0;
 
-	while (1)
-	{
-		if (mount_table[index].path == RT_NULL) break;
+    while (1)
+    {
+        if (mount_table[index].path == NULL) break;
 
-		if (dfs_mount(mount_table[index].device_name,
-				mount_table[index].path,
-				mount_table[index].filesystemtype,
-				mount_table[index].rwflag,
-				mount_table[index].data) != 0)
-		{
-			rt_kprintf("mount fs[%s] on %s failed.\n", mount_table[index].filesystemtype,
-				mount_table[index].path);
-			return -RT_ERROR;
-		}
+        if (dfs_mount(mount_table[index].device_name,
+                mount_table[index].path,
+                mount_table[index].filesystemtype,
+                mount_table[index].rwflag,
+                mount_table[index].data) != 0)
+        {
+            rt_kprintf("mount fs[%s] on %s failed.\n", mount_table[index].filesystemtype,
+                mount_table[index].path);
+            return -RT_ERROR;
+        }
 
-		index ++;
-	}
-	return 0;
+        index ++;
+    }
+    return 0;
 }
 INIT_ENV_EXPORT(dfs_mount_table);
 #endif
@@ -530,7 +541,7 @@ int df(const char *path)
     long long cap;
     struct statfs buffer;
 
-    result = dfs_statfs(path ? path : RT_NULL, &buffer);
+    result = dfs_statfs(path ? path : NULL, &buffer);
     if (result != 0)
     {
         rt_kprintf("dfs_statfs failed.\n");
diff --git a/components/dfs/src/dfs_posix.c b/components/dfs/src/dfs_posix.c
index 0f1d9569e6..ff3acb874e 100644
--- a/components/dfs/src/dfs_posix.c
+++ b/components/dfs/src/dfs_posix.c
@@ -24,6 +24,7 @@
 
 #include <dfs.h>
 #include <dfs_posix.h>
+#include "dfs_private.h"
 
 /**
  * @addtogroup FsPosixApi
@@ -50,7 +51,7 @@ int open(const char *file, int flags, int mode)
     fd = fd_new();
     if (fd < 0)
     {
-        rt_set_errno(-DFS_STATUS_ENOMEM);
+        rt_set_errno(-ENOMEM);
 
         return -1;
     }
@@ -89,9 +90,9 @@ int close(int fd)
     struct dfs_fd *d;
 
     d = fd_get(fd);
-    if (d == RT_NULL)
+    if (d == NULL)
     {
-        rt_set_errno(-DFS_STATUS_EBADF);
+        rt_set_errno(-EBADF);
 
         return -1;
     }
@@ -134,9 +135,9 @@ int read(int fd, void *buf, size_t len)
 
     /* get the fd */
     d = fd_get(fd);
-    if (d == RT_NULL)
+    if (d == NULL)
     {
-        rt_set_errno(-DFS_STATUS_EBADF);
+        rt_set_errno(-EBADF);
 
         return -1;
     }
@@ -178,9 +179,9 @@ int write(int fd, const void *buf, size_t len)
 
     /* get the fd */
     d = fd_get(fd);
-    if (d == RT_NULL)
+    if (d == NULL)
     {
-        rt_set_errno(-DFS_STATUS_EBADF);
+        rt_set_errno(-EBADF);
 
         return -1;
     }
@@ -217,29 +218,29 @@ off_t lseek(int fd, off_t offset, int whence)
     struct dfs_fd *d;
 
     d = fd_get(fd);
-    if (d == RT_NULL)
+    if (d == NULL)
     {
-        rt_set_errno(-DFS_STATUS_EBADF);
+        rt_set_errno(-EBADF);
 
         return -1;
     }
 
     switch (whence)
     {
-    case DFS_SEEK_SET:
+    case SEEK_SET:
         break;
 
-    case DFS_SEEK_CUR:
+    case SEEK_CUR:
         offset += d->pos;
         break;
 
-    case DFS_SEEK_END:
+    case SEEK_END:
         offset += d->size;
         break;
 
     default:
         fd_put(d);
-        rt_set_errno(-DFS_STATUS_EINVAL);
+        rt_set_errno(-EINVAL);
 
         return -1;
     }
@@ -247,7 +248,7 @@ off_t lseek(int fd, off_t offset, int whence)
     if (offset < 0)
     {
         fd_put(d);
-        rt_set_errno(-DFS_STATUS_EINVAL);
+        rt_set_errno(-EINVAL);
 
         return -1;
     }
@@ -357,9 +358,9 @@ int fstat(int fildes, struct stat *buf)
 
     /* get the fd */
     d = fd_get(fildes);
-    if (d == RT_NULL)
+    if (d == NULL)
     {
-        rt_set_errno(-DFS_STATUS_EBADF);
+        rt_set_errno(-EBADF);
 
         return -1;
     }
@@ -367,12 +368,12 @@ int fstat(int fildes, struct stat *buf)
     /* it's the root directory */
     buf->st_dev = 0;
 
-    buf->st_mode = DFS_S_IFREG | DFS_S_IRUSR | DFS_S_IRGRP | DFS_S_IROTH |
-                   DFS_S_IWUSR | DFS_S_IWGRP | DFS_S_IWOTH;
+    buf->st_mode = S_IFREG | S_IRUSR | S_IRGRP | S_IROTH |
+                   S_IWUSR | S_IWGRP | S_IWOTH;
     if (d->type == FT_DIRECTORY)
     {
-        buf->st_mode &= ~DFS_S_IFREG;
-        buf->st_mode |= DFS_S_IFDIR | DFS_S_IXUSR | DFS_S_IXGRP | DFS_S_IXOTH;
+        buf->st_mode &= ~S_IFREG;
+        buf->st_mode |= S_IFDIR | S_IXUSR | S_IXGRP | S_IXOTH;
     }
 
     buf->st_size    = d->size;
@@ -380,7 +381,7 @@ int fstat(int fildes, struct stat *buf)
 
     fd_put(d);
 
-    return DFS_STATUS_OK;
+    return RT_EOK;
 }
 RTM_EXPORT(fstat);
 #endif
@@ -402,9 +403,9 @@ int fsync(int fildes)
 
     /* get the fd */
     d = fd_get(fildes);
-    if (d == RT_NULL)
+    if (d == NULL)
     {
-        rt_set_errno(-DFS_STATUS_EBADF);
+        rt_set_errno(-EBADF);
         return -1;
     }
 
@@ -427,28 +428,28 @@ RTM_EXPORT(fsync);
  * @return 0 on successful completion. Otherwise, -1 shall be returned and errno
  * set to indicate the error.
  */
-int ioctl(int fildes, long cmd, void *data)
+int ioctl(int fildes, int cmd, void *data)
 {
-	int ret;
+    int ret;
     struct dfs_fd *d;
 
     /* get the fd */
     d = fd_get(fildes);
-    if (d == RT_NULL)
+    if (d == NULL)
     {
-        rt_set_errno(-DFS_STATUS_EBADF);
+        rt_set_errno(-EBADF);
         return -1;
     }
 
-	ret = dfs_file_ioctl(d, cmd, data);
-	if (ret != DFS_STATUS_OK)
-	{
-		rt_set_errno(ret);
-		ret = -1;
-	}
+    ret = dfs_file_ioctl(d, cmd, data);
+    if (ret != 0)
+    {
+        rt_set_errno(ret);
+        ret = -1;
+    }
     fd_put(d);
 
-	return ret;
+    return ret;
 }
 RTM_EXPORT(ioctl);
 
@@ -494,14 +495,14 @@ int mkdir(const char *path, mode_t mode)
     fd = fd_new();
     if (fd == -1)
     {
-        rt_set_errno(-DFS_STATUS_ENOMEM);
+        rt_set_errno(-ENOMEM);
 
         return -1;
     }
 
     d = fd_get(fd);
 
-    result = dfs_file_open(d, path, DFS_O_DIRECTORY | DFS_O_CREAT);
+    result = dfs_file_open(d, path, O_DIRECTORY | O_CREAT);
 
     if (result < 0)
     {
@@ -561,31 +562,32 @@ DIR *opendir(const char *name)
     int fd, result;
     DIR *t;
 
-    t = RT_NULL;
+    t = NULL;
 
     /* allocate a fd */
     fd = fd_new();
     if (fd == -1)
     {
-        rt_set_errno(-DFS_STATUS_ENOMEM);
+        rt_set_errno(-ENOMEM);
 
-        return RT_NULL;
+        return NULL;
     }
     d = fd_get(fd);
 
-    result = dfs_file_open(d, name, DFS_O_RDONLY | DFS_O_DIRECTORY);
+    result = dfs_file_open(d, name, O_RDONLY | O_DIRECTORY);
     if (result >= 0)
     {
         /* open successfully */
         t = (DIR *) rt_malloc(sizeof(DIR));
-        if (t == RT_NULL)
+        if (t == NULL)
         {
             dfs_file_close(d);
             fd_put(d);
         }
         else
         {
-            rt_memset(t, 0, sizeof(DIR));
+            memset(t, 0, sizeof(DIR));
+
             t->fd = fd;
         }
         fd_put(d);
@@ -598,7 +600,7 @@ DIR *opendir(const char *name)
     fd_put(d);
     rt_set_errno(result);
 
-    return RT_NULL;
+    return NULL;
 }
 RTM_EXPORT(opendir);
 
@@ -617,10 +619,10 @@ struct dirent *readdir(DIR *d)
     struct dfs_fd *fd;
 
     fd = fd_get(d->fd);
-    if (fd == RT_NULL)
+    if (fd == NULL)
     {
-        rt_set_errno(-DFS_STATUS_EBADF);
-        return RT_NULL;
+        rt_set_errno(-EBADF);
+        return NULL;
     }
 
     if (d->num)
@@ -641,7 +643,7 @@ struct dirent *readdir(DIR *d)
             fd_put(fd);
             rt_set_errno(result);
 
-            return RT_NULL;
+            return NULL;
         }
 
         d->num = result;
@@ -668,9 +670,9 @@ long telldir(DIR *d)
     long result;
 
     fd = fd_get(d->fd);
-    if (fd == RT_NULL)
+    if (fd == NULL)
     {
-        rt_set_errno(-DFS_STATUS_EBADF);
+        rt_set_errno(-EBADF);
 
         return 0;
     }
@@ -694,9 +696,9 @@ void seekdir(DIR *d, off_t offset)
     struct dfs_fd *fd;
 
     fd = fd_get(d->fd);
-    if (fd == RT_NULL)
+    if (fd == NULL)
     {
-        rt_set_errno(-DFS_STATUS_EBADF);
+        rt_set_errno(-EBADF);
 
         return ;
     }
@@ -719,9 +721,9 @@ void rewinddir(DIR *d)
     struct dfs_fd *fd;
 
     fd = fd_get(d->fd);
-    if (fd == RT_NULL)
+    if (fd == NULL)
     {
-        rt_set_errno(-DFS_STATUS_EBADF);
+        rt_set_errno(-EBADF);
 
         return ;
     }
@@ -747,9 +749,9 @@ int closedir(DIR *d)
     struct dfs_fd *fd;
 
     fd = fd_get(d->fd);
-    if (fd == RT_NULL)
+    if (fd == NULL)
     {
-        rt_set_errno(-DFS_STATUS_EBADF);
+        rt_set_errno(-EBADF);
 
         return -1;
     }
@@ -785,7 +787,7 @@ int chdir(const char *path)
     char *fullpath;
     DIR *d;
 
-    if (path == RT_NULL)
+    if (path == NULL)
     {
         dfs_lock();
         rt_kprintf("%s\n", working_directory);
@@ -794,24 +796,24 @@ int chdir(const char *path)
         return 0;
     }
 
-    if (rt_strlen(path) > DFS_PATH_MAX)
+    if (strlen(path) > DFS_PATH_MAX)
     {
-        rt_set_errno(-DFS_STATUS_ENOTDIR);
+        rt_set_errno(-ENOTDIR);
 
         return -1;
     }
 
     fullpath = dfs_normalize_path(NULL, path);
-    if (fullpath == RT_NULL)
+    if (fullpath == NULL)
     {
-        rt_set_errno(-DFS_STATUS_ENOTDIR);
+        rt_set_errno(-ENOTDIR);
 
         return -1; /* build path failed */
     }
 
     dfs_lock();
     d = opendir(fullpath);
-    if (d == RT_NULL)
+    if (d == NULL)
     {
         rt_free(fullpath);
         /* this is a not exist directory */
@@ -840,6 +842,25 @@ FINSH_FUNCTION_EXPORT_ALIAS(chdir, cd, change current working directory);
 #endif
 
 /**
+ * this function is a POSIX compliant version, which shall check the file named
+ * by the pathname pointed to by the path argument for accessibility according
+ * to the bit pattern contained in amode.
+ *
+ * @param path the specified file/dir path.
+ * @param amode the value is either the bitwise-inclusive OR of the access
+ * permissions to be checked (R_OK, W_OK, X_OK) or the existence test (F_OK).
+ */
+int access(const char *path, int amode)
+{
+    struct stat sb;
+    if (stat(path, &sb) < 0)
+        return -1; /* already sets errno */
+
+    /* ignore R_OK,W_OK,X_OK condition */
+    return 0;
+}
+
+/**
  * this function is a POSIX compliant version, which will return current
  * working directory.
  *
@@ -852,7 +873,7 @@ char *getcwd(char *buf, size_t size)
 {
 #ifdef DFS_USING_WORKDIR
     rt_enter_critical();
-    rt_strncpy(buf, working_directory, size);
+    strncpy(buf, working_directory, size);
     rt_exit_critical();
 #else
     rt_kprintf(NO_WORKING_DIR);
diff --git a/components/dfs/src/poll.c b/components/dfs/src/poll.c
new file mode 100644
index 0000000000..b0bd234647
--- /dev/null
+++ b/components/dfs/src/poll.c
@@ -0,0 +1,227 @@
+/*
+ * File      : poll.c
+ * This file is part of RT-Thread RTOS
+ * COPYRIGHT (C) 2006 - 2017, RT-Thread Development Team
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License along
+ *  with this program; if not, write to the Free Software Foundation, Inc.,
+ *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Change Logs:
+ * Date           Author       Notes
+ * 2016-12-28     Bernard      first version
+ */
+#include <stdint.h>
+
+#include <rtdevice.h>
+
+#include <dfs.h>
+#include <dfs_file.h>
+#include <dfs_posix.h>
+
+struct rt_poll_node;
+
+struct rt_poll_table
+{
+    rt_pollreq_t req;
+    rt_uint32_t triggered; /* the waited thread whether triggered */
+    rt_thread_t polling_thread;
+    struct rt_poll_node *nodes;
+};
+
+struct rt_poll_node
+{
+    struct rt_wqueue_node wqn;
+    struct rt_poll_table *pt;
+    struct rt_poll_node *next;
+};
+
+static int __wqueue_pollwake(struct rt_wqueue_node *wait, void *key)
+{
+    struct rt_poll_node *pn;
+
+    if (key && !((rt_uint32_t)key & wait->key))
+        return -1;
+
+    pn = rt_container_of(wait, struct rt_poll_node, wqn);
+    pn->pt->triggered = 1;
+
+    return __wqueue_default_wake(wait, key);
+}
+
+static void _poll_add(rt_wqueue_t *wq, rt_pollreq_t *req)
+{
+    struct rt_poll_table *pt;
+    struct rt_poll_node *node;
+
+    node = rt_malloc(sizeof(struct rt_poll_node));
+    if (node == RT_NULL)
+        return;
+
+    pt = rt_container_of(req, struct rt_poll_table, req);
+
+    node->wqn.key = req->_key;
+    rt_list_init(&(node->wqn.list));
+    node->wqn.polling_thread = pt->polling_thread;
+    node->wqn.wakeup = __wqueue_pollwake;
+    node->next = pt->nodes;
+    node->pt = pt;
+    pt->nodes = node;
+    rt_wqueue_add(wq, &node->wqn);
+}
+
+static void poll_table_init(struct rt_poll_table *pt)
+{
+    pt->req._proc = _poll_add;
+    pt->triggered = 0;
+    pt->nodes = RT_NULL;
+    pt->polling_thread = rt_thread_self();
+}
+
+static int poll_wait_timeout(struct rt_poll_table *pt, int msec)
+{
+    rt_int32_t timeout;
+    int ret = 0;
+    struct rt_thread *thread;
+    rt_base_t level;
+
+    thread = pt->polling_thread;
+
+    timeout = rt_tick_from_millisecond(msec);
+
+    level = rt_hw_interrupt_disable();
+
+    if (timeout != 0 && !pt->triggered)
+    {
+        rt_thread_suspend(thread);
+        if (timeout > 0)
+        {
+            rt_timer_control(&(thread->thread_timer),
+                             RT_TIMER_CTRL_SET_TIME,
+                             &timeout);
+            rt_timer_start(&(thread->thread_timer));
+        }
+
+        rt_hw_interrupt_enable(level);
+
+        rt_schedule();
+    }
+    else
+    {
+        rt_hw_interrupt_enable(level);
+    }
+
+    ret = !pt->triggered;
+
+    return ret;
+}
+
+static int do_pollfd(struct pollfd *pollfd, rt_pollreq_t *req)
+{
+    int mask = 0;
+    int fd;
+
+    fd = pollfd->fd;
+
+    if (fd >= 0)
+    {
+        struct dfs_fd *f = fd_get(fd);
+        mask = POLLNVAL;
+
+        if (f)
+        {
+            mask = POLLMASK_DEFAULT;
+            if (f->fops->poll)
+            {
+                req->_key = pollfd->events | POLLERR| POLLHUP;
+
+                mask = f->fops->poll(f, req);
+            }
+            /* Mask out unneeded events. */
+            mask &= pollfd->events | POLLERR | POLLHUP;
+            fd_put(f);
+        }
+    }
+    pollfd->revents = mask;
+
+    return mask;
+}
+
+static int poll_do(struct pollfd *fds, nfds_t nfds, struct rt_poll_table *pt, int msec)
+{
+    int num;
+    int istimeout = 0;
+    int n;
+    struct pollfd *pf;
+
+    if (msec == 0)
+    {
+        pt->req._proc = RT_NULL;
+        istimeout = 1;
+    }
+
+    while (1)
+    {
+        pf = fds;
+        num = 0;
+
+        for (n = 0; n < nfds; n ++)
+        {
+            if (do_pollfd(pf, &pt->req))
+            {
+                num ++;
+                pt->req._proc = RT_NULL;
+            }
+            pf ++;
+        }
+
+        pt->req._proc = RT_NULL;
+
+        if (num || istimeout)
+            break;
+
+        if (poll_wait_timeout(pt, msec))
+            istimeout = 1;
+    }
+
+    return num;
+}
+
+static void poll_teardown(struct rt_poll_table *pt)
+{
+    struct rt_poll_node *node, *next;
+
+    next = pt->nodes;
+    while (next)
+    {
+        node = next;
+        rt_wqueue_remove(&node->wqn);
+        next = node->next;
+        rt_free(node);
+    }
+}
+
+int poll(struct pollfd *fds, nfds_t nfds, int timeout)
+{
+    int num;
+    struct rt_poll_table table;
+
+    poll_table_init(&table);
+
+    num = poll_do(fds, nfds, &table, timeout);
+	
+    poll_teardown(&table);
+
+    return num;
+}
+
diff --git a/components/dfs/src/select.c b/components/dfs/src/select.c
new file mode 100644
index 0000000000..44ba9f68a2
--- /dev/null
+++ b/components/dfs/src/select.c
@@ -0,0 +1,174 @@
+/*
+ * File      : select.c
+ * This file is part of RT-Thread RTOS
+ * COPYRIGHT (C) 2006 - 2017, RT-Thread Development Team
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License along
+ *  with this program; if not, write to the Free Software Foundation, Inc.,
+ *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Change Logs:
+ * Date           Author       Notes
+ * 2016-12-28     Bernard      first version
+ */
+#include <dfs.h>
+#include <dfs_fs.h>
+#include <dfs_posix.h>
+
+int select(int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds, struct timeval *timeout)
+{
+    int fd;
+    int npfds;
+    int msec;
+    int ndx;
+    int ret;
+    struct pollfd *pollset = RT_NULL;
+
+    /* How many pollfd structures do we need to allocate? */
+    for (fd = 0, npfds = 0; fd < nfds; fd++)
+    {
+        /* Check if any monitor operation is requested on this fd */
+        if ((readfds   && FD_ISSET(fd, readfds))  ||
+            (writefds  && FD_ISSET(fd, writefds)) ||
+            (exceptfds && FD_ISSET(fd, exceptfds)))
+        {
+            npfds++;
+        }
+    }
+
+    /* Allocate the descriptor list for poll() */
+    if (npfds > 0)
+    {
+        pollset = (struct pollfd *)rt_malloc(npfds * sizeof(struct pollfd));
+        if (!pollset)
+        {
+            return -1;
+        }
+    }
+
+    /* Initialize the descriptor list for poll() */
+    for (fd = 0, ndx = 0; fd < nfds; fd++)
+    {
+        int incr = 0;
+
+        /* The readfs set holds the set of FDs that the caller can be assured
+         * of reading from without blocking.  Note that POLLHUP is included as
+         * a read-able condition.  POLLHUP will be reported at the end-of-file
+         * or when a connection is lost.  In either case, the read() can then
+         * be performed without blocking.
+         */
+
+        if (readfds && FD_ISSET(fd, readfds))
+        {
+            pollset[ndx].fd         = fd;
+            pollset[ndx].events |= POLLIN;
+            incr = 1;
+        }
+
+        if (writefds && FD_ISSET(fd, writefds))
+        {
+            pollset[ndx].fd      = fd;
+            pollset[ndx].events |= POLLOUT;
+            incr = 1;
+        }
+
+        if (exceptfds && FD_ISSET(fd, exceptfds))
+        {
+            pollset[ndx].fd = fd;
+            incr = 1;
+        }
+
+        ndx += incr;
+    }
+
+    RT_ASSERT(ndx == npfds);
+
+    /* Convert the timeout to milliseconds */
+    if (timeout)
+    {
+        msec = timeout->tv_sec * 1000 + timeout->tv_usec / 1000;
+    }
+    else
+    {
+        msec = -1;
+    }
+
+    /* Then let poll do all of the real work. */
+
+    ret = poll(pollset, npfds, msec);
+
+    /* Now set up the return values */
+    if (readfds)
+    {
+        memset(readfds, 0, sizeof(fd_set));
+    }
+
+    if (writefds)
+    {
+        memset(writefds, 0, sizeof(fd_set));
+    }
+
+    if (exceptfds)
+    {
+        memset(exceptfds, 0, sizeof(fd_set));
+    }
+
+    /* Convert the poll descriptor list back into selects 3 bitsets */
+
+    if (ret > 0)
+    {
+        ret = 0;
+        for (ndx = 0; ndx < npfds; ndx++)
+        {
+            /* Check for read conditions.  Note that POLLHUP is included as a
+             * read condition.  POLLHUP will be reported when no more data will
+             * be available (such as when a connection is lost).  In either
+             * case, the read() can then be performed without blocking.
+             */
+
+            if (readfds)
+            {
+                if (pollset[ndx].revents & (POLLIN | POLLHUP))
+                {
+                    FD_SET(pollset[ndx].fd, readfds);
+                    ret++;
+                }
+            }
+
+            /* Check for write conditions */
+            if (writefds)
+            {
+                if (pollset[ndx].revents & POLLOUT)
+                {
+                    FD_SET(pollset[ndx].fd, writefds);
+                    ret++;
+                }
+            }
+
+            /* Check for exceptions */
+            if (exceptfds)
+            {
+                if (pollset[ndx].revents & POLLERR)
+                {
+                    FD_SET(pollset[ndx].fd, exceptfds);
+                    ret++;
+                }
+            }
+        }
+    }
+
+    if (pollset) rt_free(pollset);
+
+    return ret;
+}
+