Merge remote-tracking branch 'tinyusb/master' into pr-osal-spin-deinit

Signed-off-by: HiFiPhile <[email protected]>

1 files changed, 339 insertions, 329 deletions

diff --git a/src/class/cdc/cdc_host.c b/src/class/cdc/cdc_host.c
index beef03eff..4441222c8 100644
--- a/src/class/cdc/cdc_host.c
+++ b/src/class/cdc/cdc_host.c
@@ -29,6 +29,8 @@
 
 #include "tusb_option.h"
 
+#include <stdint.h>
+
 #if (CFG_TUH_ENABLED && CFG_TUH_CDC)
 
 #include "host/usbh.h"
@@ -41,13 +43,14 @@
 #include "serial/pl2303.h"
 
 // Level where CFG_TUSB_DEBUG must be at least for this driver is logged
-#ifndef CFG_TUH_CDC_LOG_LEVEL
-  #define CFG_TUH_CDC_LOG_LEVEL   2
-#endif
+  #ifndef CFG_TUH_CDC_LOG_LEVEL
+    #define CFG_TUH_CDC_LOG_LEVEL 2
+  #endif
 
-#define TU_LOG_DRV(...)                 TU_LOG(CFG_TUH_CDC_LOG_LEVEL, __VA_ARGS__)
-#define TU_LOG_CDC(_cdc, _format, ...)  TU_LOG_DRV("[:%u:%u] CDCh %s " _format "\r\n", _cdc->daddr, _cdc->bInterfaceNumber, \
-                                                    serial_drivers[_cdc->serial_drid].name, ##__VA_ARGS__)
+  #define TU_LOG_DRV(...) TU_LOG(CFG_TUH_CDC_LOG_LEVEL, __VA_ARGS__)
+  #define TU_LOG_CDC(_cdc, _format, ...)                                                \
+    TU_LOG_DRV("[:%u:%u] CDCh %s " _format "\r\n", _cdc->daddr, _cdc->bInterfaceNumber, \
+               serial_drivers[_cdc->serial_drid].name, ##__VA_ARGS__)
 
 //--------------------------------------------------------------------+
 // Host CDC Interface
@@ -96,6 +99,7 @@ typedef struct {
 typedef struct {
   TUH_EPBUF_DEF(tx, CFG_TUH_CDC_TX_EPSIZE);
   TUH_EPBUF_DEF(rx, CFG_TUH_CDC_RX_EPSIZE);
+  TUH_EPBUF_DEF(ctrl, 8);
 } cdch_epbuf_t;
 
 static cdch_interface_t cdch_data[CFG_TUH_CDC];
@@ -113,63 +117,59 @@ static void cdch_set_line_coding_stage1_baudrate_complete(tuh_xfer_t *xfer);
 static void cdch_set_line_coding_stage2_data_format_complete(tuh_xfer_t *xfer);
 
 //------------- ACM prototypes -------------//
-static bool acm_open(uint8_t daddr, tusb_desc_interface_t const * itf_desc, uint16_t max_len);
-static bool acm_process_set_config(cdch_interface_t *p_cdc, tuh_xfer_t *xfer);
-static void acm_internal_control_complete(cdch_interface_t *p_cdc, tuh_xfer_t *xfer);
-
-static bool acm_set_line_coding(cdch_interface_t * p_cdc, tuh_xfer_cb_t complete_cb, uintptr_t user_data);
-static bool acm_set_control_line_state(cdch_interface_t * p_cdc, tuh_xfer_cb_t complete_cb, uintptr_t user_data);
+static uint16_t acm_open(uint8_t daddr, const tusb_desc_interface_t *itf_desc, uint16_t max_len);
+static bool     acm_process_set_config(cdch_interface_t *p_cdc, tuh_xfer_t *xfer);
+static void     acm_internal_control_complete(cdch_interface_t *p_cdc, tuh_xfer_t *xfer);
+static bool     acm_set_line_coding(cdch_interface_t *p_cdc, tuh_xfer_cb_t complete_cb, uintptr_t user_data);
+static bool     acm_set_control_line_state(cdch_interface_t *p_cdc, tuh_xfer_cb_t complete_cb, uintptr_t user_data);
 
-//------------- FTDI prototypes -------------//
-#if CFG_TUH_CDC_FTDI
+  //------------- FTDI prototypes -------------//
+  #if CFG_TUH_CDC_FTDI
 static uint16_t const ftdi_vid_pid_list[][2] = {CFG_TUH_CDC_FTDI_VID_PID_LIST};
-static bool ftdi_open(uint8_t daddr, const tusb_desc_interface_t * itf_desc, uint16_t max_len);
-static bool ftdi_proccess_set_config(cdch_interface_t *p_cdc, tuh_xfer_t *xfer);
-static void ftdi_internal_control_complete(cdch_interface_t* p_cdc, tuh_xfer_t *xfer);
 
-static bool ftdi_set_baudrate(cdch_interface_t * p_cdc, tuh_xfer_cb_t complete_cb, uintptr_t user_data);
-static bool ftdi_set_data_format(cdch_interface_t * p_cdc, tuh_xfer_cb_t complete_cb, uintptr_t user_data);
-static bool ftdi_set_modem_ctrl(cdch_interface_t * p_cdc, tuh_xfer_cb_t complete_cb, uintptr_t user_data);
-#endif
+static uint16_t ftdi_open(uint8_t daddr, const tusb_desc_interface_t *itf_desc, uint16_t max_len);
+static bool     ftdi_process_set_config(cdch_interface_t *p_cdc, tuh_xfer_t *xfer);
+static void     ftdi_internal_control_complete(cdch_interface_t *p_cdc, tuh_xfer_t *xfer);
+static bool     ftdi_set_baudrate(cdch_interface_t *p_cdc, tuh_xfer_cb_t complete_cb, uintptr_t user_data);
+static bool     ftdi_set_data_format(cdch_interface_t *p_cdc, tuh_xfer_cb_t complete_cb, uintptr_t user_data);
+static bool     ftdi_set_modem_ctrl(cdch_interface_t *p_cdc, tuh_xfer_cb_t complete_cb, uintptr_t user_data);
+  #endif
 
-//------------- CP210X prototypes -------------//
-#if CFG_TUH_CDC_CP210X
+  //------------- CP210X prototypes -------------//
+  #if CFG_TUH_CDC_CP210X
 static uint16_t const cp210x_vid_pid_list[][2] = {CFG_TUH_CDC_CP210X_VID_PID_LIST};
 
-static bool cp210x_open(uint8_t daddr, tusb_desc_interface_t const * itf_desc, uint16_t max_len);
-static bool cp210x_process_set_config(cdch_interface_t *p_cdc, tuh_xfer_t *xfer);
-static void cp210x_internal_control_complete(cdch_interface_t *p_cdc, tuh_xfer_t *xfer);
-
-static bool cp210x_set_baudrate(cdch_interface_t * p_cdc, tuh_xfer_cb_t complete_cb, uintptr_t user_data);
-static bool cp210x_set_data_format(cdch_interface_t * p_cdc, tuh_xfer_cb_t complete_cb, uintptr_t user_data);
-static bool cp210x_set_modem_ctrl(cdch_interface_t * p_cdc, tuh_xfer_cb_t complete_cb, uintptr_t user_data);
-#endif
+static uint16_t cp210x_open(uint8_t daddr, const tusb_desc_interface_t *itf_desc, uint16_t max_len);
+static bool     cp210x_process_set_config(cdch_interface_t *p_cdc, tuh_xfer_t *xfer);
+static void     cp210x_internal_control_complete(cdch_interface_t *p_cdc, tuh_xfer_t *xfer);
+static bool     cp210x_set_baudrate(cdch_interface_t *p_cdc, tuh_xfer_cb_t complete_cb, uintptr_t user_data);
+static bool     cp210x_set_data_format(cdch_interface_t *p_cdc, tuh_xfer_cb_t complete_cb, uintptr_t user_data);
+static bool     cp210x_set_modem_ctrl(cdch_interface_t *p_cdc, tuh_xfer_cb_t complete_cb, uintptr_t user_data);
+  #endif
 
-//------------- CH34x prototypes -------------//
-#if CFG_TUH_CDC_CH34X
+  //------------- CH34x prototypes -------------//
+  #if CFG_TUH_CDC_CH34X
 static uint16_t const ch34x_vid_pid_list[][2] = {CFG_TUH_CDC_CH34X_VID_PID_LIST};
 
-static bool ch34x_open(uint8_t daddr, tusb_desc_interface_t const * itf_desc, uint16_t max_len);
-static bool ch34x_process_set_config(cdch_interface_t *p_cdc, tuh_xfer_t *xfer);
-static void ch34x_internal_control_complete(cdch_interface_t *p_cdc, tuh_xfer_t *xfer);
-
-static bool ch34x_set_baudrate(cdch_interface_t * p_cdc, tuh_xfer_cb_t complete_cb, uintptr_t user_data);
-static bool ch34x_set_data_format(cdch_interface_t * p_cdc, tuh_xfer_cb_t complete_cb, uintptr_t user_data);
-static bool ch34x_set_modem_ctrl(cdch_interface_t * p_cdc, tuh_xfer_cb_t complete_cb, uintptr_t user_data);
-#endif
+static uint16_t ch34x_open(uint8_t daddr, const tusb_desc_interface_t *itf_desc, uint16_t max_len);
+static bool     ch34x_process_set_config(cdch_interface_t *p_cdc, tuh_xfer_t *xfer);
+static void     ch34x_internal_control_complete(cdch_interface_t *p_cdc, tuh_xfer_t *xfer);
+static bool     ch34x_set_baudrate(cdch_interface_t *p_cdc, tuh_xfer_cb_t complete_cb, uintptr_t user_data);
+static bool     ch34x_set_data_format(cdch_interface_t *p_cdc, tuh_xfer_cb_t complete_cb, uintptr_t user_data);
+static bool     ch34x_set_modem_ctrl(cdch_interface_t *p_cdc, tuh_xfer_cb_t complete_cb, uintptr_t user_data);
+  #endif
 
-//------------- PL2303 prototypes -------------//
-#if CFG_TUH_CDC_PL2303
+  //------------- PL2303 prototypes -------------//
+  #if CFG_TUH_CDC_PL2303
 static uint16_t const pl2303_vid_pid_list[][2] = {CFG_TUH_CDC_PL2303_VID_PID_LIST};
 static const pl2303_type_data_t pl2303_type_data[PL2303_TYPE_COUNT] = {PL2303_TYPE_DATA};
 
-static bool pl2303_open(uint8_t daddr, tusb_desc_interface_t const * itf_desc, uint16_t max_len);
-static bool pl2303_process_set_config(cdch_interface_t *p_cdc, tuh_xfer_t *xfer);
-static void pl2303_internal_control_complete(cdch_interface_t *p_cdc, tuh_xfer_t *xfer);
-
-static bool pl2303_set_line_coding(cdch_interface_t * p_cdc, tuh_xfer_cb_t complete_cb, uintptr_t user_data);
-static bool pl2303_set_modem_ctrl(cdch_interface_t * p_cdc, tuh_xfer_cb_t complete_cb, uintptr_t user_data);
-#endif
+static uint16_t pl2303_open(uint8_t daddr, const tusb_desc_interface_t *itf_desc, uint16_t max_len);
+static bool     pl2303_process_set_config(cdch_interface_t *p_cdc, tuh_xfer_t *xfer);
+static void     pl2303_internal_control_complete(cdch_interface_t *p_cdc, tuh_xfer_t *xfer);
+static bool     pl2303_set_line_coding(cdch_interface_t *p_cdc, tuh_xfer_cb_t complete_cb, uintptr_t user_data);
+static bool     pl2303_set_modem_ctrl(cdch_interface_t *p_cdc, tuh_xfer_cb_t complete_cb, uintptr_t user_data);
+  #endif
 
 //------------- Common -------------//
 enum {
@@ -197,11 +197,12 @@ enum {
 typedef bool (*serial_driver_func_t)(cdch_interface_t * p_cdc, tuh_xfer_cb_t complete_cb, uintptr_t user_data);
 
 typedef struct {
-  uint16_t const (*vid_pid_list)[2];
-  uint16_t const vid_pid_count;
-  bool (*const open)(uint8_t daddr, const tusb_desc_interface_t * itf_desc, uint16_t max_len);
-  bool (*const process_set_config)(cdch_interface_t * p_cdc, tuh_xfer_t * xfer);
-  void (*const request_complete)(cdch_interface_t * p_cdc, tuh_xfer_t * xfer); // internal request complete handler to update line state
+  const uint16_t (*vid_pid_list)[2];
+  const uint16_t vid_pid_count;
+  uint16_t (*const open)(uint8_t daddr, const tusb_desc_interface_t *itf_desc, uint16_t max_len);
+  bool (*const process_set_config)(cdch_interface_t *p_cdc, tuh_xfer_t *xfer);
+  // internal request complete handler to update line state
+  void (*const request_complete)(cdch_interface_t *p_cdc, tuh_xfer_t *xfer);
 
   serial_driver_func_t set_control_line_state, set_baudrate, set_data_format, set_line_coding;
 
@@ -216,88 +217,91 @@ typedef struct {
   #define DRIVER_NAME_DECLARE(_str)
 #endif
 
+// clang-format off
 // Note driver list must be in the same order as SERIAL_DRIVER enum
 static const cdch_serial_driver_t serial_drivers[] = {
   {
-      .vid_pid_list           = NULL,
-      .vid_pid_count          = 0,
-      .open                   = acm_open,
-      .process_set_config     = acm_process_set_config,
-      .request_complete       = acm_internal_control_complete,
-      .set_control_line_state = acm_set_control_line_state,
-      .set_baudrate           = acm_set_line_coding,
-      .set_data_format        = acm_set_line_coding,
-      .set_line_coding        = acm_set_line_coding,
-      DRIVER_NAME_DECLARE("ACM")
+    .vid_pid_list           = NULL,
+    .vid_pid_count          = 0,
+    .open                   = acm_open,
+    .process_set_config     = acm_process_set_config,
+    .request_complete       = acm_internal_control_complete,
+    .set_control_line_state = acm_set_control_line_state,
+    .set_baudrate           = acm_set_line_coding,
+    .set_data_format        = acm_set_line_coding,
+    .set_line_coding        = acm_set_line_coding,
+    DRIVER_NAME_DECLARE("ACM")
   },
 
   #if CFG_TUH_CDC_FTDI
   {
-      .vid_pid_list           = ftdi_vid_pid_list,
-      .vid_pid_count          = TU_ARRAY_SIZE(ftdi_vid_pid_list),
-      .open                   = ftdi_open,
-      .process_set_config     = ftdi_proccess_set_config,
-      .request_complete       = ftdi_internal_control_complete,
-      .set_control_line_state = ftdi_set_modem_ctrl,
-      .set_baudrate           = ftdi_set_baudrate,
-      .set_data_format        = ftdi_set_data_format,
-      .set_line_coding        = NULL, // 2 stage set line coding
-      DRIVER_NAME_DECLARE("FTDI")
+    .vid_pid_list           = ftdi_vid_pid_list,
+    .vid_pid_count          = TU_ARRAY_SIZE(ftdi_vid_pid_list),
+    .open                   = ftdi_open,
+    .process_set_config     = ftdi_process_set_config,
+    .request_complete       = ftdi_internal_control_complete,
+    .set_control_line_state = ftdi_set_modem_ctrl,
+    .set_baudrate           = ftdi_set_baudrate,
+    .set_data_format        = ftdi_set_data_format,
+    .set_line_coding        = NULL, // 2 stage set line coding
+    DRIVER_NAME_DECLARE("FTDI")
   },
   #endif
 
   #if CFG_TUH_CDC_CP210X
   {
-      .vid_pid_list           = cp210x_vid_pid_list,
-      .vid_pid_count          = TU_ARRAY_SIZE(cp210x_vid_pid_list),
-      .open                   = cp210x_open,
-      .process_set_config     = cp210x_process_set_config,
-      .request_complete       = cp210x_internal_control_complete,
-      .set_control_line_state = cp210x_set_modem_ctrl,
-      .set_baudrate           = cp210x_set_baudrate,
-      .set_data_format        = cp210x_set_data_format,
-      .set_line_coding        = NULL, // 2 stage set line coding
-      DRIVER_NAME_DECLARE("CP210x")
+    .vid_pid_list           = cp210x_vid_pid_list,
+    .vid_pid_count          = TU_ARRAY_SIZE(cp210x_vid_pid_list),
+    .open                   = cp210x_open,
+    .process_set_config     = cp210x_process_set_config,
+    .request_complete       = cp210x_internal_control_complete,
+    .set_control_line_state = cp210x_set_modem_ctrl,
+    .set_baudrate           = cp210x_set_baudrate,
+    .set_data_format        = cp210x_set_data_format,
+    .set_line_coding        = NULL, // 2 stage set line coding
+    DRIVER_NAME_DECLARE("CP210x")
   },
   #endif
 
   #if CFG_TUH_CDC_CH34X
   {
-      .vid_pid_list           = ch34x_vid_pid_list,
-      .vid_pid_count          = TU_ARRAY_SIZE(ch34x_vid_pid_list),
-      .open                   = ch34x_open,
-      .process_set_config     = ch34x_process_set_config,
-      .request_complete       = ch34x_internal_control_complete,
+    .vid_pid_list           = ch34x_vid_pid_list,
+    .vid_pid_count          = TU_ARRAY_SIZE(ch34x_vid_pid_list),
+    .open                   = ch34x_open,
+    .process_set_config     = ch34x_process_set_config,
+    .request_complete       = ch34x_internal_control_complete,
 
-      .set_control_line_state = ch34x_set_modem_ctrl,
-      .set_baudrate           = ch34x_set_baudrate,
-      .set_data_format        = ch34x_set_data_format,
-      .set_line_coding        = NULL, // 2 stage set line coding
-      DRIVER_NAME_DECLARE("CH34x")
+    .set_control_line_state = ch34x_set_modem_ctrl,
+    .set_baudrate           = ch34x_set_baudrate,
+    .set_data_format        = ch34x_set_data_format,
+    .set_line_coding        = NULL, // 2 stage set line coding
+    DRIVER_NAME_DECLARE("CH34x")
   },
   #endif
 
   #if CFG_TUH_CDC_PL2303
   {
-      .vid_pid_list           = pl2303_vid_pid_list,
-      .vid_pid_count          = TU_ARRAY_SIZE(pl2303_vid_pid_list),
-      .open                   = pl2303_open,
-      .process_set_config     = pl2303_process_set_config,
-      .request_complete       = pl2303_internal_control_complete,
-      .set_control_line_state = pl2303_set_modem_ctrl,
-      .set_baudrate           = pl2303_set_line_coding,
-      .set_data_format        = pl2303_set_line_coding,
-      .set_line_coding        = pl2303_set_line_coding,
-      DRIVER_NAME_DECLARE("PL2303")
+    .vid_pid_list           = pl2303_vid_pid_list,
+    .vid_pid_count          = TU_ARRAY_SIZE(pl2303_vid_pid_list),
+    .open                   = pl2303_open,
+    .process_set_config     = pl2303_process_set_config,
+    .request_complete       = pl2303_internal_control_complete,
+    .set_control_line_state = pl2303_set_modem_ctrl,
+    .set_baudrate           = pl2303_set_line_coding,
+    .set_data_format        = pl2303_set_line_coding,
+    .set_line_coding        = pl2303_set_line_coding,
+    DRIVER_NAME_DECLARE("PL2303")
   }
   #endif
 };
+// clang-format on
 
 TU_VERIFY_STATIC(TU_ARRAY_SIZE(serial_drivers) == SERIAL_DRIVER_COUNT, "Serial driver count mismatch");
 
 //--------------------------------------------------------------------+
 // INTERNAL OBJECT & FUNCTION DECLARATION
 //--------------------------------------------------------------------+
+static bool open_ep_stream_pair(cdch_interface_t *p_cdc, const tusb_desc_endpoint_t *desc_ep);
 
 TU_ATTR_ALWAYS_INLINE static inline cdch_interface_t * get_itf(uint8_t idx) {
   TU_ASSERT(idx < CFG_TUH_CDC, NULL);
@@ -364,7 +368,7 @@ static cdch_interface_t* get_itf_by_xfer(const tuh_xfer_t * xfer) {
         #endif
 
         default:
-          break;
+          break; // unknown driver
       }
     }
   }
@@ -389,8 +393,6 @@ static cdch_interface_t * make_new_itf(uint8_t daddr, tusb_desc_interface_t cons
   return NULL;
 }
 
-static bool open_ep_stream_pair(cdch_interface_t * p_cdc , tusb_desc_endpoint_t const *desc_ep);
-
 //--------------------------------------------------------------------+
 // Weak stubs: invoked if no strong implementation is available
 //--------------------------------------------------------------------+
@@ -471,25 +473,26 @@ bool tuh_cdc_get_line_coding_local(uint8_t idx, cdc_line_coding_t * line_coding)
 uint32_t tuh_cdc_write(uint8_t idx, void const * buffer, uint32_t bufsize) {
   cdch_interface_t * p_cdc = get_itf(idx);
   TU_VERIFY(p_cdc);
-  return tu_edpt_stream_write(p_cdc->daddr, &p_cdc->stream.tx, buffer, bufsize);
+  return tu_edpt_stream_write(&p_cdc->stream.tx, buffer, bufsize);
 }
 
 uint32_t tuh_cdc_write_flush(uint8_t idx) {
   cdch_interface_t * p_cdc = get_itf(idx);
   TU_VERIFY(p_cdc);
-  return tu_edpt_stream_write_xfer(p_cdc->daddr, &p_cdc->stream.tx);
+  return tu_edpt_stream_write_xfer(&p_cdc->stream.tx);
 }
 
 bool tuh_cdc_write_clear(uint8_t idx) {
   cdch_interface_t * p_cdc = get_itf(idx);
   TU_VERIFY(p_cdc);
-  return tu_edpt_stream_clear(&p_cdc->stream.tx);
+  tu_edpt_stream_clear(&p_cdc->stream.tx);
+  return true;
 }
 
 uint32_t tuh_cdc_write_available(uint8_t idx) {
   cdch_interface_t * p_cdc = get_itf(idx);
   TU_VERIFY(p_cdc);
-  return tu_edpt_stream_write_available(p_cdc->daddr, &p_cdc->stream.tx);
+  return tu_edpt_stream_write_available(&p_cdc->stream.tx);
 }
 
 //--------------------------------------------------------------------+
@@ -499,7 +502,7 @@ uint32_t tuh_cdc_write_available(uint8_t idx) {
 uint32_t tuh_cdc_read (uint8_t idx, void * buffer, uint32_t bufsize) {
   cdch_interface_t * p_cdc = get_itf(idx);
   TU_VERIFY(p_cdc);
-  return tu_edpt_stream_read(p_cdc->daddr, &p_cdc->stream.rx, buffer, bufsize);
+  return tu_edpt_stream_read(&p_cdc->stream.rx, buffer, bufsize);
 }
 
 uint32_t tuh_cdc_read_available(uint8_t idx) {
@@ -518,9 +521,9 @@ bool tuh_cdc_read_clear (uint8_t idx) {
   cdch_interface_t * p_cdc = get_itf(idx);
   TU_VERIFY(p_cdc);
 
-  bool ret = tu_edpt_stream_clear(&p_cdc->stream.rx);
-  tu_edpt_stream_read_xfer(p_cdc->daddr, &p_cdc->stream.rx);
-  return ret;
+  tu_edpt_stream_clear(&p_cdc->stream.rx);
+  (void)tu_edpt_stream_read_xfer(&p_cdc->stream.rx);
+  return true;
 }
 
 //--------------------------------------------------------------------+
@@ -602,7 +605,7 @@ bool tuh_cdc_set_line_coding(uint8_t idx, cdc_line_coding_t const *line_coding,
   p_cdc->requested_line.coding = *line_coding;
   p_cdc->user_complete_cb = complete_cb;
 
-  if (driver->set_line_coding) {
+  if (driver->set_line_coding != NULL) {
     // driver support set_line_coding request
     TU_VERIFY(driver->set_line_coding(p_cdc, complete_cb ? cdch_internal_control_complete : NULL, user_data));
 
@@ -611,7 +614,7 @@ bool tuh_cdc_set_line_coding(uint8_t idx, cdc_line_coding_t const *line_coding,
     }
   } else {
     // driver does not support set_line_coding and need 2 stage to set baudrate and data format separately
-    if (complete_cb) {
+    if (complete_cb != NULL) {
       // non-blocking
       TU_VERIFY(driver->set_baudrate(p_cdc, cdch_set_line_coding_stage1_baudrate_complete, user_data));
     } else {
@@ -619,7 +622,7 @@ bool tuh_cdc_set_line_coding(uint8_t idx, cdc_line_coding_t const *line_coding,
       xfer_result_t result = XFER_RESULT_INVALID;
 
       TU_VERIFY(driver->set_baudrate(p_cdc, NULL, (uintptr_t) &result));
-      if (user_data) {
+      if (user_data != 0) {
         *((xfer_result_t *) user_data) = result;
       }
       TU_VERIFY(result == XFER_RESULT_SUCCESS);
@@ -627,7 +630,7 @@ bool tuh_cdc_set_line_coding(uint8_t idx, cdc_line_coding_t const *line_coding,
 
       result = XFER_RESULT_INVALID;
       TU_VERIFY(driver->set_data_format(p_cdc, NULL, (uintptr_t) &result));
-      if (user_data) {
+      if (user_data != 0) {
         *((xfer_result_t *) user_data) = result;
       }
       TU_VERIFY(result == XFER_RESULT_SUCCESS);
@@ -648,13 +651,10 @@ bool cdch_init(void) {
   for (size_t i = 0; i < CFG_TUH_CDC; i++) {
     cdch_interface_t *p_cdc = &cdch_data[i];
     cdch_epbuf_t *epbuf = &cdch_epbuf[i];
-    tu_edpt_stream_init(&p_cdc->stream.tx, true, true, false,
-                        p_cdc->stream.tx_ff_buf, CFG_TUH_CDC_TX_BUFSIZE,
-                        epbuf->tx, CFG_TUH_CDC_TX_EPSIZE);
-
-    tu_edpt_stream_init(&p_cdc->stream.rx, true, false, false,
-                        p_cdc->stream.rx_ff_buf, CFG_TUH_CDC_RX_BUFSIZE,
-                        epbuf->rx, CFG_TUH_CDC_RX_EPSIZE);
+    TU_ASSERT(tu_edpt_stream_init(&p_cdc->stream.tx, true, true, false, p_cdc->stream.tx_ff_buf,
+                                  CFG_TUH_CDC_TX_BUFSIZE, epbuf->tx));
+    TU_ASSERT(tu_edpt_stream_init(&p_cdc->stream.rx, true, false, false, p_cdc->stream.rx_ff_buf,
+                                  CFG_TUH_CDC_RX_BUFSIZE, epbuf->rx));
   }
 
   return true;
@@ -663,8 +663,8 @@ bool cdch_init(void) {
 bool cdch_deinit(void) {
   for (size_t i = 0; i < CFG_TUH_CDC; i++) {
     cdch_interface_t *p_cdc = &cdch_data[i];
-    tu_edpt_stream_deinit(&p_cdc->stream.tx);
-    tu_edpt_stream_deinit(&p_cdc->stream.rx);
+    (void)tu_edpt_stream_deinit(&p_cdc->stream.tx);
+    (void)tu_edpt_stream_deinit(&p_cdc->stream.rx);
   }
   return true;
 }
@@ -674,11 +674,9 @@ void cdch_close(uint8_t daddr) {
     cdch_interface_t *p_cdc = &cdch_data[idx];
     if (p_cdc->daddr == daddr) {
       TU_LOG_CDC(p_cdc, "close");
+      tuh_cdc_umount_cb(idx); // invoke callback
 
-      // Invoke application callback
-      tuh_cdc_umount_cb(idx);
-
-      p_cdc->daddr = 0;
+      p_cdc->daddr            = 0;
       p_cdc->bInterfaceNumber = 0;
       p_cdc->mounted = false;
       tu_edpt_stream_close(&p_cdc->stream.tx);
@@ -696,13 +694,12 @@ bool cdch_xfer_cb(uint8_t daddr, uint8_t ep_addr, xfer_result_t event, uint32_t
   TU_ASSERT(p_cdc);
 
   if (ep_addr == p_cdc->stream.tx.ep_addr) {
-    // invoke tx complete callback to possibly refill tx fifo
-    tuh_cdc_tx_complete_cb(idx);
+    tuh_cdc_tx_complete_cb(idx); // invoke transmit complete callback
 
-    if (0 == tu_edpt_stream_write_xfer(daddr, &p_cdc->stream.tx)) {
+    if (0 == tu_edpt_stream_write_xfer(&p_cdc->stream.tx)) {
       // If there is no data left, a ZLP should be sent if:
       // - xferred_bytes is multiple of EP Packet size and not zero
-      tu_edpt_stream_write_zlp_if_needed(daddr, &p_cdc->stream.tx, xferred_bytes);
+      (void)tu_edpt_stream_write_zlp_if_needed(&p_cdc->stream.tx, xferred_bytes);
     }
   } else if (ep_addr == p_cdc->stream.rx.ep_addr) {
     #if CFG_TUH_CDC_FTDI
@@ -718,16 +715,15 @@ bool cdch_xfer_cb(uint8_t daddr, uint8_t ep_addr, xfer_result_t event, uint32_t
     #endif
     {
       tu_edpt_stream_read_xfer_complete(&p_cdc->stream.rx, xferred_bytes);
-
       tuh_cdc_rx_cb(idx); // invoke receive callback
     }
 
     // prepare for next transfer if needed
-    tu_edpt_stream_read_xfer(daddr, &p_cdc->stream.rx);
+    tu_edpt_stream_read_xfer(&p_cdc->stream.rx);
   } else if (ep_addr == p_cdc->ep_notif) {
     // TODO handle notification endpoint
   } else {
-    TU_ASSERT(false);
+    return false;
   }
 
   return true;
@@ -736,27 +732,23 @@ bool cdch_xfer_cb(uint8_t daddr, uint8_t ep_addr, xfer_result_t event, uint32_t
 //--------------------------------------------------------------------+
 // Enumeration
 //--------------------------------------------------------------------+
-
 static bool open_ep_stream_pair(cdch_interface_t *p_cdc, tusb_desc_endpoint_t const *desc_ep) {
   for (size_t i = 0; i < 2; i++) {
-    TU_ASSERT(TUSB_DESC_ENDPOINT == desc_ep->bDescriptorType &&
-              TUSB_XFER_BULK == desc_ep->bmAttributes.xfer);
+    TU_ASSERT(TUSB_DESC_ENDPOINT == desc_ep->bDescriptorType && TUSB_XFER_BULK == desc_ep->bmAttributes.xfer, 0);
     TU_ASSERT(tuh_edpt_open(p_cdc->daddr, desc_ep));
+    const uint8_t     ep_dir = tu_edpt_dir(desc_ep->bEndpointAddress);
+    tu_edpt_stream_t *stream = (ep_dir == TUSB_DIR_IN) ? &p_cdc->stream.rx : &p_cdc->stream.tx;
+    tu_edpt_stream_open(stream, p_cdc->daddr, desc_ep, tu_edpt_packet_size(desc_ep));
+    tu_edpt_stream_clear(stream);
 
-    if (tu_edpt_dir(desc_ep->bEndpointAddress) == TUSB_DIR_IN) {
-      tu_edpt_stream_open(&p_cdc->stream.rx, desc_ep);
-    } else {
-      tu_edpt_stream_open(&p_cdc->stream.tx, desc_ep);
-    }
-
-    desc_ep = (tusb_desc_endpoint_t const *) tu_desc_next(desc_ep);
+    desc_ep = (const tusb_desc_endpoint_t *)tu_desc_next(desc_ep);
   }
 
   return true;
 }
 
-bool cdch_open(uint8_t rhport, uint8_t daddr, tusb_desc_interface_t const *itf_desc, uint16_t max_len) {
-  (void) rhport;
+uint16_t cdch_open(uint8_t rhport, uint8_t daddr, const tusb_desc_interface_t *itf_desc, uint16_t max_len) {
+  (void)rhport;
   // For CDC: only support ACM subclass
   // Note: Protocol 0xFF can be RNDIS device
   if (TUSB_CLASS_CDC == itf_desc->bInterfaceClass &&
@@ -765,52 +757,36 @@ bool cdch_open(uint8_t rhport, uint8_t daddr, tusb_desc_interface_t const *itf_d
   } else if (SERIAL_DRIVER_COUNT > 1 &&
              TUSB_CLASS_VENDOR_SPECIFIC == itf_desc->bInterfaceClass) {
     uint16_t vid, pid;
-    TU_VERIFY(tuh_vid_pid_get(daddr, &vid, &pid));
+    TU_VERIFY(tuh_vid_pid_get(daddr, &vid, &pid), 0);
 
-    for (size_t dr = 1; dr < SERIAL_DRIVER_COUNT; dr++) {
-      const cdch_serial_driver_t *driver = &serial_drivers[dr];
+    for (size_t drv = 1; drv < SERIAL_DRIVER_COUNT; drv++) {
+      const cdch_serial_driver_t *driver = &serial_drivers[drv];
       for (size_t i = 0; i < driver->vid_pid_count; i++) {
         if (driver->vid_pid_list[i][0] == vid && driver->vid_pid_list[i][1] == pid) {
-          const bool ret = driver->open(daddr, itf_desc, max_len);
-          TU_LOG_DRV("[:%u:%u] CDCh %s open %s\r\n", daddr, itf_desc->bInterfaceNumber, driver->name, ret ? "OK" : "FAILED");
-          return ret;
+          const uint16_t drv_len = driver->open(daddr, itf_desc, max_len);
+          TU_LOG_DRV("[:%u:%u] CDCh %s open %s\r\n", daddr, itf_desc->bInterfaceNumber, driver->name,
+                     drv_len > 0 ? "OK" : "FAILED");
+          return drv_len;
         }
       }
     }
+  } else {
+    // not supported class
   }
 
-  return false;
-}
-
-bool cdch_set_config(uint8_t daddr, uint8_t itf_num) {
-  tusb_control_request_t request;
-  request.wIndex = tu_htole16((uint16_t) itf_num);
-  uint8_t const idx = tuh_cdc_itf_get_index(daddr, itf_num);
-  cdch_interface_t *p_cdc = get_itf(idx);
-  TU_ASSERT(p_cdc && p_cdc->serial_drid < SERIAL_DRIVER_COUNT);
-  TU_LOG_CDC(p_cdc, "set config");
-
-  // fake transfer to kick-off process_set_config()
-  tuh_xfer_t xfer;
-  xfer.daddr = daddr;
-  xfer.result = XFER_RESULT_SUCCESS;
-  xfer.setup = &request;
-  xfer.user_data = 0; // initial state 0
-  cdch_process_set_config(&xfer);
-
-  return true;
+  return 0;
 }
 
 static void set_config_complete(cdch_interface_t *p_cdc, bool success) {
   if (success) {
     const uint8_t idx = get_idx_by_ptr(p_cdc);
-    p_cdc->mounted = true;
+    p_cdc->mounted    = true;
     tuh_cdc_mount_cb(idx);
     // Prepare for incoming data
-    tu_edpt_stream_read_xfer(p_cdc->daddr, &p_cdc->stream.rx);
+    tu_edpt_stream_read_xfer(&p_cdc->stream.rx);
   } else {
     // clear the interface entry
-    p_cdc->daddr = 0;
+    p_cdc->daddr            = 0;
     p_cdc->bInterfaceNumber = 0;
   }
 
@@ -819,6 +795,33 @@ static void set_config_complete(cdch_interface_t *p_cdc, bool success) {
   usbh_driver_set_config_complete(p_cdc->daddr, p_cdc->bInterfaceNumber + itf_offset);
 }
 
+bool cdch_set_config(uint8_t daddr, uint8_t itf_num) {
+  const uint8_t     idx   = tuh_cdc_itf_get_index(daddr, itf_num);
+  cdch_interface_t *p_cdc = get_itf(idx);
+  TU_ASSERT(p_cdc && p_cdc->serial_drid < SERIAL_DRIVER_COUNT);
+  TU_LOG_CDC(p_cdc, "set config");
+
+  // fake transfer to kick-off process_set_config()
+  tusb_control_request_t request;
+  request.wIndex = tu_htole16((uint16_t)itf_num);
+
+  tuh_xfer_t xfer;
+  xfer.daddr       = daddr;
+  xfer.ep_addr     = 0;
+  xfer.result      = XFER_RESULT_SUCCESS;
+  xfer.setup       = &request;
+  xfer.complete_cb = NULL;
+  xfer.buffer      = NULL;
+  xfer.user_data   = 0; // initial state 0
+
+  const cdch_serial_driver_t *driver = &serial_drivers[p_cdc->serial_drid];
+  if (!driver->process_set_config(p_cdc, &xfer)) {
+    set_config_complete(p_cdc, false);
+  }
+
+  return true;
+}
+
 static void cdch_process_set_config(tuh_xfer_t *xfer) {
   cdch_interface_t *p_cdc = get_itf_by_xfer(xfer);
   TU_ASSERT(p_cdc && p_cdc->serial_drid < SERIAL_DRIVER_COUNT,);
@@ -830,13 +833,16 @@ static void cdch_process_set_config(tuh_xfer_t *xfer) {
   }
 }
 
+// return false if there is no active transfer
 static bool set_line_state_on_enum(cdch_interface_t *p_cdc, tuh_xfer_t *xfer) {
   enum {
     ENUM_SET_LINE_CODING = 0,
     ENUM_SET_LINE_CONTROL,
     ENUM_SET_LINE_COMPLETE,
   };
+  #ifdef CFG_TUH_CDC_LINE_CODING_ON_ENUM
   const uint8_t idx = get_idx_by_ptr(p_cdc);
+  #endif
   const uintptr_t state = xfer->user_data;
 
   switch (state) {
@@ -894,7 +900,7 @@ static void cdch_internal_control_complete(tuh_xfer_t *xfer) {
 
   // Invoke application callback
   xfer->complete_cb = p_cdc->user_complete_cb;
-  if (xfer->complete_cb) {
+  if (xfer->complete_cb != NULL) {
     xfer->complete_cb(xfer);
   }
 }
@@ -910,7 +916,7 @@ static void cdch_set_line_coding_stage1_baudrate_complete(tuh_xfer_t *xfer) {
     TU_ASSERT(driver->set_data_format(p_cdc, cdch_set_line_coding_stage2_data_format_complete, xfer->user_data),);
   } else {
     xfer->complete_cb = p_cdc->user_complete_cb;
-    if (xfer->complete_cb) {
+    if (xfer->complete_cb != NULL) {
       xfer->complete_cb(xfer);
     }
   }
@@ -926,7 +932,7 @@ static void cdch_set_line_coding_stage2_data_format_complete(tuh_xfer_t *xfer) {
   }
 
   xfer->complete_cb = p_cdc->user_complete_cb;
-  if (xfer->complete_cb) {
+  if (xfer->complete_cb != NULL) {
     xfer->complete_cb(xfer);
   }
 }
@@ -950,12 +956,12 @@ static void acm_internal_control_complete(cdch_interface_t *p_cdc, tuh_xfer_t *x
       break;
 
     default:
-      break;
+      break; // unknown request
   }
 }
 
 static bool acm_set_control_line_state(cdch_interface_t *p_cdc, tuh_xfer_cb_t complete_cb, uintptr_t user_data) {
-  TU_VERIFY(p_cdc->acm.capability.support_line_request);
+  TU_VERIFY(p_cdc->acm.capability.support_line_request != 0);
 
   const tusb_control_request_t request = {
     .bmRequestType_bit = {
@@ -982,7 +988,7 @@ static bool acm_set_control_line_state(cdch_interface_t *p_cdc, tuh_xfer_cb_t co
 }
 
 static bool acm_set_line_coding(cdch_interface_t *p_cdc, tuh_xfer_cb_t complete_cb, uintptr_t user_data) {
-  TU_VERIFY(p_cdc->acm.capability.support_line_request);
+  TU_VERIFY(p_cdc->acm.capability.support_line_request != 0);
   TU_VERIFY((p_cdc->requested_line.coding.data_bits >= 5 && p_cdc->requested_line.coding.data_bits <= 8) ||
             p_cdc->requested_line.coding.data_bits == 16);
 
@@ -998,15 +1004,16 @@ static bool acm_set_line_coding(cdch_interface_t *p_cdc, tuh_xfer_cb_t complete_
     .wLength  = tu_htole16((uint16_t) sizeof(cdc_line_coding_t))
   };
 
-  // use usbh enum buf to hold line coding since user line_coding variable does not live long enough
-  uint8_t *enum_buf = usbh_get_enum_buf();
-  memcpy(enum_buf, &p_cdc->requested_line.coding, sizeof(cdc_line_coding_t));
+  // use local ctrl buf to hold line coding since user line_coding variable does not live long enough
+  uint8_t const idx = get_idx_by_ptr(p_cdc);
+  uint8_t *ctrl_buf = cdch_epbuf[idx].ctrl;
+  memcpy(ctrl_buf, &p_cdc->requested_line.coding, sizeof(cdc_line_coding_t));
 
   tuh_xfer_t xfer = {
     .daddr       = p_cdc->daddr,
     .ep_addr     = 0,
     .setup       = &request,
-    .buffer      = enum_buf,
+    .buffer      = ctrl_buf,
     .complete_cb = complete_cb,
     .user_data   = user_data
   };
@@ -1019,19 +1026,19 @@ enum {
   CONFIG_ACM_COMPLETE = 0
 };
 
-static bool acm_open(uint8_t daddr, tusb_desc_interface_t const *itf_desc, uint16_t max_len) {
-  uint8_t const *p_desc_end = ((uint8_t const *) itf_desc) + max_len;
+static uint16_t acm_open(uint8_t daddr, const tusb_desc_interface_t *itf_desc, uint16_t max_len) {
+  const uint8_t *p_desc   = (const uint8_t *)itf_desc;
+  const uint8_t *desc_end = p_desc + max_len;
 
   cdch_interface_t *p_cdc = make_new_itf(daddr, itf_desc);
-  TU_VERIFY(p_cdc);
-
+  TU_VERIFY(p_cdc, 0);
   p_cdc->serial_drid = SERIAL_DRIVER_ACM;
 
   //------------- Control Interface -------------//
-  uint8_t const *p_desc = tu_desc_next(itf_desc);
+  p_desc = tu_desc_next(p_desc);
 
   // Communication Functional Descriptors
-  while ((p_desc < p_desc_end) && (TUSB_DESC_CS_INTERFACE == tu_desc_type(p_desc))) {
+  while ((p_desc < desc_end) && (TUSB_DESC_CS_INTERFACE == tu_desc_type(p_desc))) {
     if (CDC_FUNC_DESC_ABSTRACT_CONTROL_MANAGEMENT == cdc_functional_desc_typeof(p_desc)) {
       // save ACM bmCapabilities
       p_cdc->acm.capability = ((cdc_desc_func_acm_t const *) p_desc)->bmCapabilities;
@@ -1042,26 +1049,27 @@ static bool acm_open(uint8_t daddr, tusb_desc_interface_t const *itf_desc, uint1
 
   // Open notification endpoint of control interface if any
   if (itf_desc->bNumEndpoints == 1) {
-    TU_ASSERT(TUSB_DESC_ENDPOINT == tu_desc_type(p_desc));
-    tusb_desc_endpoint_t const *desc_ep = (tusb_desc_endpoint_t const *) p_desc;
-
-    TU_ASSERT(tuh_edpt_open(daddr, desc_ep));
+    TU_ASSERT(TUSB_DESC_ENDPOINT == tu_desc_type(p_desc), 0);
+    const tusb_desc_endpoint_t *desc_ep = (const tusb_desc_endpoint_t *)p_desc;
+    TU_ASSERT(tuh_edpt_open(daddr, desc_ep), 0);
     p_cdc->ep_notif = desc_ep->bEndpointAddress;
 
     p_desc = tu_desc_next(p_desc);
   }
 
   //------------- Data Interface (if any) -------------//
-  if ((TUSB_DESC_INTERFACE == tu_desc_type(p_desc)) &&
-      (TUSB_CLASS_CDC_DATA == ((tusb_desc_interface_t const *) p_desc)->bInterfaceClass)) {
-    // next to endpoint descriptor
-    p_desc = tu_desc_next(p_desc);
+  if (TUSB_DESC_INTERFACE == tu_desc_type(p_desc)) {
+    const tusb_desc_interface_t *data_itf = (const tusb_desc_interface_t *)p_desc;
+    if (data_itf->bInterfaceClass == TUSB_CLASS_CDC_DATA) {
+      p_desc = tu_desc_next(p_desc); // next to endpoint descriptor
 
-    // data endpoints expected to be in pairs
-    TU_ASSERT(open_ep_stream_pair(p_cdc, (tusb_desc_endpoint_t const *) p_desc));
+      // data endpoints expected to be in pairs
+      TU_ASSERT(open_ep_stream_pair(p_cdc, (const tusb_desc_endpoint_t *)p_desc), 0);
+      p_desc += data_itf->bNumEndpoints * sizeof(tusb_desc_endpoint_t);
+    }
   }
 
-  return true;
+  return (uint16_t)((uintptr_t)p_desc - (uintptr_t)itf_desc);
 }
 
 static bool acm_process_set_config(cdch_interface_t *p_cdc, tuh_xfer_t *xfer) {
@@ -1136,7 +1144,6 @@ static inline bool ftdi_sio_reset(cdch_interface_t *p_cdc, tuh_xfer_cb_t complet
 
 // internal control complete to update state such as line state, line_coding
 static void ftdi_internal_control_complete(cdch_interface_t* p_cdc, tuh_xfer_t *xfer) {
-  TU_VERIFY(xfer->result == XFER_RESULT_SUCCESS,);
   const tusb_control_request_t * setup = xfer->setup;
   if (xfer->result == XFER_RESULT_SUCCESS) {
     if (setup->bRequest      == FTDI_SIO_SET_MODEM_CTRL_REQUEST &&
@@ -1168,10 +1175,10 @@ static bool ftdi_set_data_format(cdch_interface_t *p_cdc, tuh_xfer_cb_t complete
 
 static bool ftdi_set_baudrate(cdch_interface_t *p_cdc, tuh_xfer_cb_t complete_cb, uintptr_t user_data) {
   uint32_t index_value = ftdi_get_divisor(p_cdc);
-  TU_VERIFY(index_value);
+  TU_VERIFY(index_value != 0);
   uint16_t value = (uint16_t) index_value;
   uint16_t index = (uint16_t) (index_value >> 16);
-  if (p_cdc->ftdi.channel) {
+  if (p_cdc->ftdi.channel != 0) {
     index = (uint16_t) ((index << 8) | p_cdc->ftdi.channel);
   }
 
@@ -1195,46 +1202,40 @@ enum {
   CONFIG_FTDI_COMPLETE
 };
 
-static bool ftdi_open(uint8_t daddr, const tusb_desc_interface_t *itf_desc, uint16_t max_len) {
+static uint16_t ftdi_open(uint8_t daddr, const tusb_desc_interface_t *itf_desc, uint16_t max_len) {
   // FTDI Interface includes 1 vendor interface + 2 bulk endpoints
   TU_VERIFY(itf_desc->bInterfaceSubClass == 0xff && itf_desc->bInterfaceProtocol == 0xff &&
-            itf_desc->bNumEndpoints == 2);
-  TU_VERIFY(sizeof(tusb_desc_interface_t) + 2 * sizeof(tusb_desc_endpoint_t) <= max_len);
+              itf_desc->bNumEndpoints == 2,
+            0);
+  const uint16_t drv_len =
+    (uint16_t)(sizeof(tusb_desc_interface_t) + itf_desc->bNumEndpoints * sizeof(tusb_desc_endpoint_t));
+  TU_VERIFY(drv_len <= max_len, 0);
 
   cdch_interface_t *p_cdc = make_new_itf(daddr, itf_desc);
-  TU_VERIFY(p_cdc);
+  TU_VERIFY(p_cdc, 0);
 
   p_cdc->serial_drid = SERIAL_DRIVER_FTDI;
 
   // endpoint pair
-  tusb_desc_endpoint_t const *desc_ep = (tusb_desc_endpoint_t const *) tu_desc_next(itf_desc);
+  const tusb_desc_endpoint_t *desc_ep = (const tusb_desc_endpoint_t *)tu_desc_next(itf_desc);
 
-  /*
-   * NOTE: Some customers have programmed FT232R/FT245R devices
-   * with an endpoint size of 0 - not good.
-   */
-  TU_ASSERT(desc_ep->wMaxPacketSize != 0);
+  /* NOTE: Some users have programmed FT232R/FT245R devices
+   * with an endpoint size of 0 !!! */
+  TU_ASSERT(desc_ep->wMaxPacketSize != 0, 0);
 
-  // data endpoints expected to be in pairs
-  return open_ep_stream_pair(p_cdc, desc_ep);
+  TU_ASSERT(open_ep_stream_pair(p_cdc, desc_ep), 0);
+
+  return drv_len;
 }
 
-static bool ftdi_proccess_set_config(cdch_interface_t *p_cdc, tuh_xfer_t *xfer) {
+static bool ftdi_process_set_config(cdch_interface_t *p_cdc, tuh_xfer_t *xfer) {
   TU_ASSERT(xfer->result == XFER_RESULT_SUCCESS);
   const uintptr_t state = xfer->user_data;
   switch (state) {
     // from here sequence overtaken from Linux Kernel function ftdi_port_probe()
     case CONFIG_FTDI_DETERMINE_TYPE:
       // determine type
-      if (p_cdc->bInterfaceNumber == 0) {
-        TU_ASSERT(ftdi_determine_type(p_cdc));
-      } else {
-        // other interfaces have same type as interface 0
-        uint8_t const idx_itf0 = tuh_cdc_itf_get_index(xfer->daddr, 0);
-        cdch_interface_t const *p_cdc_itf0 = get_itf(idx_itf0);
-        TU_ASSERT(p_cdc_itf0);
-        p_cdc->ftdi.chip_type = p_cdc_itf0->ftdi.chip_type;
-      }
+      TU_ASSERT(ftdi_determine_type(p_cdc));
       TU_ATTR_FALLTHROUGH;
 
     case CONFIG_FTDI_WRITE_LATENCY:
@@ -1365,7 +1366,7 @@ static uint32_t ftdi_232bm_baud_base_to_divisor(uint32_t baud, uint32_t base) {
   uint8_t divfrac[8] = {0, 3, 2, 4, 1, 5, 6, 7};
   uint32_t divisor;
   /* divisor shifted 3 bits to the left */
-  uint32_t divisor3 = DIV_ROUND_CLOSEST(base, 2 * baud);
+  uint32_t divisor3 = tu_div_round_nearest(base, 2 * baud);
   divisor = divisor3 >> 3;
   divisor |= (uint32_t) divfrac[divisor3 & 0x7] << 14;
   /* Deal with special cases for highest baud rates. */
@@ -1373,6 +1374,8 @@ static uint32_t ftdi_232bm_baud_base_to_divisor(uint32_t baud, uint32_t base) {
     divisor = 0;
   } else if (divisor == 0x4001) /* 1.5 */ {
     divisor = 1;
+  } else {
+    // nothing to do
   }
   return divisor;
 }
@@ -1387,7 +1390,7 @@ static uint32_t ftdi_2232h_baud_base_to_divisor(uint32_t baud, uint32_t base) {
   uint32_t divisor3;
 
   /* hi-speed baud rate is 10-bit sampling instead of 16-bit */
-  divisor3 = DIV_ROUND_CLOSEST(8 * base, 10 * baud);
+  divisor3 = tu_div_round_nearest(8 * base, 10 * baud);
 
   divisor = divisor3 >> 3;
   divisor |= (uint32_t) divfrac[divisor3 & 0x7] << 14;
@@ -1396,12 +1399,13 @@ static uint32_t ftdi_2232h_baud_base_to_divisor(uint32_t baud, uint32_t base) {
     divisor = 0;
   } else if (divisor == 0x4001) /* 1.5 */ {
     divisor = 1;
+  } else {
+    // nothing to do
   }
-  /*
-   * Set this bit to turn off a divide by 2.5 on baud rate generator
+
+  /* Set this bit to turn off a divide by 2.5 on baud rate generator
    * This enables baud rates up to 12Mbaud but cannot reach below 1200
-   * baud with this bit set
-   */
+   * baud with this bit set */
   divisor |= 0x00020000;
   return divisor;
 }
@@ -1413,7 +1417,7 @@ static inline uint32_t ftdi_2232h_baud_to_divisor(uint32_t baud) {
 static inline uint32_t ftdi_get_divisor(cdch_interface_t *p_cdc) {
   uint32_t baud = p_cdc->requested_line.coding.bit_rate;
   uint32_t div_value = 0;
-  TU_VERIFY(baud);
+  TU_VERIFY(baud != 0);
 
   switch (p_cdc->ftdi.chip_type) {
     case FTDI_UNKNOWN:
@@ -1489,7 +1493,7 @@ static inline uint32_t ftdi_get_divisor(cdch_interface_t *p_cdc) {
 //------------- Control Request -------------//
 
 static bool cp210x_set_request(cdch_interface_t * p_cdc, uint8_t command, uint16_t value,
-                               uint8_t * buffer, uint16_t length, tuh_xfer_cb_t complete_cb, uintptr_t user_data) {
+                               uint8_t const * buffer, uint16_t length, tuh_xfer_cb_t complete_cb, uintptr_t user_data) {
   tusb_control_request_t const request = {
     .bmRequestType_bit = {
       .recipient = TUSB_REQ_RCPT_INTERFACE,
@@ -1502,19 +1506,20 @@ static bool cp210x_set_request(cdch_interface_t * p_cdc, uint8_t command, uint16
     .wLength  = tu_htole16(length)
   };
 
-  // use usbh enum buf since application variable does not live long enough
-  uint8_t * enum_buf = NULL;
+  // use local ctrl buf since application variable does not live long enough
+  uint8_t * ctrl_buf = NULL;
 
   if (buffer && length > 0) {
-    enum_buf = usbh_get_enum_buf();
-    tu_memcpy_s(enum_buf, CFG_TUH_ENUMERATION_BUFSIZE, buffer, length);
+    uint8_t const idx = get_idx_by_ptr(p_cdc);
+    ctrl_buf = cdch_epbuf[idx].ctrl;
+    tu_memcpy_s(ctrl_buf, sizeof(cdch_epbuf[idx].ctrl), buffer, length);
   }
 
   tuh_xfer_t xfer = {
     .daddr       = p_cdc->daddr,
     .ep_addr     = 0,
     .setup       = &request,
-    .buffer      = enum_buf,
+    .buffer      = ctrl_buf,
     .complete_cb = complete_cb,
     .user_data   = user_data
   };
@@ -1553,14 +1558,15 @@ static void cp210x_internal_control_complete(cdch_interface_t *p_cdc, tuh_xfer_t
       p_cdc->line.coding.bit_rate = p_cdc->requested_line.coding.bit_rate;
       break;
 
-    default: break;
+    default:
+      break; // unsupported request
   }
 }
 
 static bool cp210x_set_baudrate(cdch_interface_t *p_cdc, tuh_xfer_cb_t complete_cb, uintptr_t user_data) {
   // Not every baud rate is supported. See datasheets and AN205 "CP210x Baud Rate Support"
   uint32_t baud_le = tu_htole32(p_cdc->requested_line.coding.bit_rate);
-  return cp210x_set_request(p_cdc, CP210X_SET_BAUDRATE, 0, (uint8_t *) &baud_le, 4, complete_cb, user_data);
+  return cp210x_set_request(p_cdc, CP210X_SET_BAUDRATE, 0, (uint8_t const *) &baud_le, 4, complete_cb, user_data);
 }
 
 static bool cp210x_set_data_format(cdch_interface_t *p_cdc, tuh_xfer_cb_t complete_cb, uintptr_t user_data) {
@@ -1583,21 +1589,23 @@ enum {
   CONFIG_CP210X_COMPLETE
 };
 
-static bool cp210x_open(uint8_t daddr, tusb_desc_interface_t const *itf_desc, uint16_t max_len) {
+static uint16_t cp210x_open(uint8_t daddr, const tusb_desc_interface_t *itf_desc, uint16_t max_len) {
   // CP210x Interface includes 1 vendor interface + 2 bulk endpoints
-  TU_VERIFY(itf_desc->bInterfaceSubClass == 0 && itf_desc->bInterfaceProtocol == 0 && itf_desc->bNumEndpoints == 2);
-  TU_VERIFY(sizeof(tusb_desc_interface_t) + 2 * sizeof(tusb_desc_endpoint_t) <= max_len);
+  TU_VERIFY(itf_desc->bInterfaceSubClass == 0 && itf_desc->bInterfaceProtocol == 0 && itf_desc->bNumEndpoints == 2, 0);
+  const uint16_t drv_len =
+    (uint16_t)(sizeof(tusb_desc_interface_t) + itf_desc->bNumEndpoints * sizeof(tusb_desc_endpoint_t));
+  TU_VERIFY(drv_len <= max_len, 0);
 
   cdch_interface_t *p_cdc = make_new_itf(daddr, itf_desc);
-  TU_VERIFY(p_cdc);
+  TU_VERIFY(p_cdc, 0);
 
   p_cdc->serial_drid = SERIAL_DRIVER_CP210X;
 
-  // endpoint pair
-  tusb_desc_endpoint_t const *desc_ep = (tusb_desc_endpoint_t const *) tu_desc_next(itf_desc);
-
   // data endpoints expected to be in pairs
-  return open_ep_stream_pair(p_cdc, desc_ep);
+  const tusb_desc_endpoint_t *desc_ep = (const tusb_desc_endpoint_t *)tu_desc_next(itf_desc);
+  TU_ASSERT(open_ep_stream_pair(p_cdc, desc_ep));
+
+  return drv_len;
 }
 
 static bool cp210x_process_set_config(cdch_interface_t *p_cdc, tuh_xfer_t *xfer) {
@@ -1635,7 +1643,7 @@ static uint16_t ch34x_get_divisor_prescaler(cdch_interface_t *p_cdc);
 //------------- Control Request -------------//
 
 static bool ch34x_set_request(cdch_interface_t *p_cdc, uint8_t direction, uint8_t request,
-                              uint16_t value, uint16_t index, uint8_t *buffer, uint16_t length,
+                              uint16_t value, uint16_t index, uint8_t const *buffer, uint16_t length,
                               tuh_xfer_cb_t complete_cb, uintptr_t user_data) {
   tusb_control_request_t const request_setup = {
       .bmRequestType_bit = {
@@ -1649,13 +1657,14 @@ static bool ch34x_set_request(cdch_interface_t *p_cdc, uint8_t direction, uint8_
       .wLength  = tu_htole16(length)
   };
 
-  // use usbh enum buf since application variable does not live long enough
-  uint8_t *enum_buf = NULL;
+  // use local ctrl buf since application variable does not live long enough
+  uint8_t *ctrl_buf = NULL;
 
-  if (buffer && length > 0) {
-    enum_buf = usbh_get_enum_buf();
-    if (direction == TUSB_DIR_OUT) {
-      tu_memcpy_s(enum_buf, CFG_TUH_ENUMERATION_BUFSIZE, buffer, length);
+  if (length > 0) {
+    uint8_t const idx = get_idx_by_ptr(p_cdc);
+    ctrl_buf = cdch_epbuf[idx].ctrl;
+    if (buffer && direction == TUSB_DIR_OUT) {
+      tu_memcpy_s(ctrl_buf, sizeof(cdch_epbuf[idx].ctrl), buffer, length);
     }
   }
 
@@ -1663,7 +1672,7 @@ static bool ch34x_set_request(cdch_interface_t *p_cdc, uint8_t direction, uint8_
       .daddr       = p_cdc->daddr,
       .ep_addr     = 0,
       .setup       = &request_setup,
-      .buffer      = enum_buf,
+      .buffer      = ctrl_buf,
       .complete_cb = complete_cb,
       .user_data   = user_data
   };
@@ -1677,8 +1686,8 @@ TU_ATTR_ALWAYS_INLINE static inline bool ch34x_control_out(cdch_interface_t *p_c
 }
 
 TU_ATTR_ALWAYS_INLINE static inline bool ch34x_control_in(cdch_interface_t *p_cdc, uint8_t request, uint16_t value, uint16_t index,
-                                                          uint8_t *buffer, uint16_t buffersize, tuh_xfer_cb_t complete_cb, uintptr_t user_data) {
-  return ch34x_set_request(p_cdc, TUSB_DIR_IN, request, value, index, buffer, buffersize,
+                                                          uint16_t buffersize, tuh_xfer_cb_t complete_cb, uintptr_t user_data) {
+  return ch34x_set_request(p_cdc, TUSB_DIR_IN, request, value, index, NULL, buffersize,
                            complete_cb, user_data);
 }
 
@@ -1687,12 +1696,6 @@ TU_ATTR_ALWAYS_INLINE static inline bool ch34x_write_reg(cdch_interface_t *p_cdc
   return ch34x_control_out(p_cdc, CH34X_REQ_WRITE_REG, reg, reg_value, complete_cb, user_data);
 }
 
-//static bool ch34x_read_reg_request ( cdch_interface_t * p_cdc, uint16_t reg,
-//                                     uint8_t *buffer, uint16_t buffersize, tuh_xfer_cb_t complete_cb, uintptr_t user_data )
-//{
-//  return ch34x_control_in ( p_cdc, CH34X_REQ_READ_REG, reg, 0, buffer, buffersize, complete_cb, user_data );
-//}
-
 //------------- Driver API -------------//
 
 // internal control complete to update state such as line state, encoding
@@ -1714,7 +1717,8 @@ static void ch34x_internal_control_complete(cdch_interface_t *p_cdc, tuh_xfer_t
           p_cdc->line.coding.data_bits = p_cdc->requested_line.coding.data_bits;
           break;
 
-        default: break;
+        default:
+          break; // unsupported
       }
       break;
 
@@ -1722,19 +1726,20 @@ static void ch34x_internal_control_complete(cdch_interface_t *p_cdc, tuh_xfer_t
       p_cdc->line.control_state = p_cdc->requested_line.control_state;
       break;
 
-    default: break;
+    default:
+      break; // unsupported request
   }
 }
 
 static bool ch34x_set_data_format(cdch_interface_t *p_cdc, tuh_xfer_cb_t complete_cb, uintptr_t user_data) {
   const uint8_t lcr = ch34x_get_lcr(p_cdc);
-  TU_VERIFY(lcr);
+  TU_VERIFY(lcr > 0);
   return ch34x_write_reg(p_cdc, CH32X_REG16_LCR2_LCR, lcr, complete_cb, user_data);
 }
 
 static bool ch34x_set_baudrate(cdch_interface_t *p_cdc, tuh_xfer_cb_t complete_cb, uintptr_t user_data) {
   const uint16_t div_ps = ch34x_get_divisor_prescaler(p_cdc);
-  TU_VERIFY(div_ps);
+  TU_VERIFY(div_ps > 0);
   return ch34x_write_reg(p_cdc, CH34X_REG16_DIVISOR_PRESCALER, div_ps, complete_cb, user_data);
 }
 
@@ -1755,29 +1760,30 @@ enum {
   CONFIG_CH34X_COMPLETE
 };
 
-static bool ch34x_open(uint8_t daddr, tusb_desc_interface_t const * itf_desc, uint16_t max_len) {
+static uint16_t ch34x_open(uint8_t daddr, const tusb_desc_interface_t *itf_desc, uint16_t max_len) {
   // CH34x Interface includes 1 vendor interface + 2 bulk + 1 interrupt endpoints
-  TU_VERIFY(itf_desc->bNumEndpoints == 3);
-  TU_VERIFY(sizeof(tusb_desc_interface_t) + 3 * sizeof(tusb_desc_endpoint_t) <= max_len);
+  TU_VERIFY(itf_desc->bNumEndpoints == 3, 0);
+  const uint16_t drv_len =
+    (uint16_t)(sizeof(tusb_desc_interface_t) + itf_desc->bNumEndpoints * sizeof(tusb_desc_endpoint_t));
+  TU_VERIFY(drv_len <= max_len, 0);
 
   cdch_interface_t * p_cdc = make_new_itf(daddr, itf_desc);
-  TU_VERIFY(p_cdc);
+  TU_VERIFY(p_cdc, 0);
 
   p_cdc->serial_drid = SERIAL_DRIVER_CH34X;
 
-  tusb_desc_endpoint_t const * desc_ep = (tusb_desc_endpoint_t const *) tu_desc_next(itf_desc);
+  const tusb_desc_endpoint_t *desc_ep = (const tusb_desc_endpoint_t *)tu_desc_next(itf_desc);
 
   // data endpoints expected to be in pairs
-  TU_ASSERT(open_ep_stream_pair(p_cdc, desc_ep));
-  desc_ep += 2;
+  TU_ASSERT(open_ep_stream_pair(p_cdc, desc_ep), 0);
+  desc_ep = (const tusb_desc_endpoint_t *)((uintptr_t)desc_ep + 2 * sizeof(tusb_desc_endpoint_t));
 
   // Interrupt endpoint: not used for now
-  TU_ASSERT(TUSB_DESC_ENDPOINT == tu_desc_type(desc_ep) &&
-            TUSB_XFER_INTERRUPT == desc_ep->bmAttributes.xfer);
-  TU_ASSERT(tuh_edpt_open(daddr, desc_ep));
+  TU_ASSERT(TUSB_DESC_ENDPOINT == tu_desc_type(desc_ep) && TUSB_XFER_INTERRUPT == desc_ep->bmAttributes.xfer, 0);
+  TU_ASSERT(tuh_edpt_open(daddr, desc_ep), 0);
   p_cdc->ep_notif = desc_ep->bEndpointAddress;
 
-  return true;
+  return drv_len;
 }
 
 static bool ch34x_process_set_config(cdch_interface_t *p_cdc, tuh_xfer_t *xfer) {
@@ -1786,8 +1792,7 @@ static bool ch34x_process_set_config(cdch_interface_t *p_cdc, tuh_xfer_t *xfer)
 
   switch (state) {
     case CONFIG_CH34X_READ_VERSION: {
-      uint8_t* enum_buf = usbh_get_enum_buf();
-      TU_ASSERT(ch34x_control_in(p_cdc, CH34X_REQ_READ_VERSION, 0, 0, enum_buf, 2,
+      TU_ASSERT(ch34x_control_in(p_cdc, CH34X_REQ_READ_VERSION, 0, 0, 2,
                                  cdch_process_set_config, CONFIG_CH34X_SERIAL_INIT));
       break;
     }
@@ -1917,7 +1922,8 @@ static uint8_t ch34x_get_lcr(cdch_interface_t *p_cdc) {
       lcr |= CH34X_LCR_ENABLE_PAR | CH34X_LCR_MARK_SPACE | CH34X_LCR_PAR_EVEN;
       break;
 
-    default: break;
+    default:
+      break; // invalid parity
   }
 
   // 1.5 stop bits not supported
@@ -1941,7 +1947,7 @@ static bool pl2303_encode_baud_rate(cdch_interface_t *p_cdc, uint8_t buf[PL2303_
 
 //------------- Control Request -------------//
 static bool pl2303_set_request(cdch_interface_t *p_cdc, uint8_t request, uint8_t requesttype,
-                               uint16_t value, uint16_t index, uint8_t *buffer, uint16_t length,
+                               uint16_t value, uint16_t index, uint8_t const *buffer, uint16_t length,
                                tuh_xfer_cb_t complete_cb, uintptr_t user_data) {
   tusb_control_request_t const request_setup = {
     .bmRequestType = requesttype,
@@ -1951,13 +1957,14 @@ static bool pl2303_set_request(cdch_interface_t *p_cdc, uint8_t request, uint8_t
     .wLength       = tu_htole16(length)
   };
 
-  // use usbh enum buf since application variable does not live long enough
-  uint8_t *enum_buf = NULL;
+  // use local ctrl buf since application variable does not live long enough
+  uint8_t *ctrl_buf = NULL;
 
-  if (buffer && length > 0) {
-    enum_buf = usbh_get_enum_buf();
-    if (request_setup.bmRequestType_bit.direction == TUSB_DIR_OUT) {
-      tu_memcpy_s(enum_buf, CFG_TUH_ENUMERATION_BUFSIZE, buffer, length);
+  if (length > 0) {
+    uint8_t const idx = get_idx_by_ptr(p_cdc);
+    ctrl_buf = cdch_epbuf[idx].ctrl;
+    if (buffer && request_setup.bmRequestType_bit.direction == TUSB_DIR_OUT) {
+      tu_memcpy_s(ctrl_buf, sizeof(cdch_epbuf[idx].ctrl), buffer, length);
     }
   }
 
@@ -1965,7 +1972,7 @@ static bool pl2303_set_request(cdch_interface_t *p_cdc, uint8_t request, uint8_t
     .daddr       = p_cdc->daddr,
     .ep_addr     = 0,
     .setup       = &request_setup,
-    .buffer      = enum_buf,
+    .buffer      = ctrl_buf,
     .complete_cb = complete_cb,
     .user_data   = user_data
   };
@@ -1973,10 +1980,10 @@ static bool pl2303_set_request(cdch_interface_t *p_cdc, uint8_t request, uint8_t
   return tuh_control_xfer(&xfer);
 }
 
-static bool pl2303_vendor_read(cdch_interface_t *p_cdc, uint16_t value, uint8_t *buf,
+static bool pl2303_vendor_read(cdch_interface_t *p_cdc, uint16_t value,
                                tuh_xfer_cb_t complete_cb, uintptr_t user_data) {
   uint8_t request = p_cdc->pl2303.type == PL2303_TYPE_HXN ? PL2303_VENDOR_READ_NREQUEST : PL2303_VENDOR_READ_REQUEST;
-  return pl2303_set_request(p_cdc, request, PL2303_VENDOR_READ_REQUEST_TYPE, value, 0, buf, 1, complete_cb, user_data);
+  return pl2303_set_request(p_cdc, request, PL2303_VENDOR_READ_REQUEST_TYPE, value, 0, NULL, 1, complete_cb, user_data);
 }
 
 static bool pl2303_vendor_write(cdch_interface_t *p_cdc, uint16_t value, uint16_t index,
@@ -1986,9 +1993,8 @@ static bool pl2303_vendor_write(cdch_interface_t *p_cdc, uint16_t value, uint16_
 }
 
 static inline bool pl2303_supports_hx_status(cdch_interface_t *p_cdc, tuh_xfer_cb_t complete_cb, uintptr_t user_data) {
-  uint8_t buf = 0;
   return pl2303_set_request(p_cdc, PL2303_VENDOR_READ_REQUEST, PL2303_VENDOR_READ_REQUEST_TYPE, PL2303_READ_TYPE_HX_STATUS, 0,
-                            &buf, 1, complete_cb, user_data);
+                            NULL, 1, complete_cb, user_data);
 }
 
 //static bool pl2303_get_line_request(cdch_interface_t * p_cdc, uint8_t buf[PL2303_LINE_CODING_BUFSIZE]) {
@@ -2000,13 +2006,15 @@ static inline bool pl2303_supports_hx_status(cdch_interface_t *p_cdc, tuh_xfer_c
 //  return pl2303_set_request(p_cdc, PL2303_BREAK_REQUEST, PL2303_BREAK_REQUEST_TYPE, state, 0, NULL, 0);
 //}
 
-static inline int pl2303_clear_halt(cdch_interface_t *p_cdc, uint8_t endp, tuh_xfer_cb_t complete_cb, uintptr_t user_data) {
+static inline bool
+pl2303_clear_halt(cdch_interface_t *p_cdc, uint8_t endp, tuh_xfer_cb_t complete_cb, uintptr_t user_data) {
   /* we don't care if it wasn't halted first. in fact some devices
    * (like some ibmcam model 1 units) seem to expect hosts to make
    * this request for iso endpoints, which can't halt!
    */
-  return pl2303_set_request(p_cdc, TUSB_REQ_CLEAR_FEATURE, PL2303_CLEAR_HALT_REQUEST_TYPE, TUSB_REQ_FEATURE_EDPT_HALT, endp,
-                            NULL, 0, complete_cb, user_data);
+  return pl2303_set_request(
+      p_cdc, TUSB_REQ_CLEAR_FEATURE, PL2303_CLEAR_HALT_REQUEST_TYPE, TUSB_REQ_FEATURE_EDPT_HALT, endp, NULL, 0,
+      complete_cb, user_data);
 }
 
 //------------- Driver API -------------//
@@ -2088,13 +2096,15 @@ enum {
   CONFIG_PL2303_COMPLETE
 };
 
-static bool pl2303_open(uint8_t daddr, tusb_desc_interface_t const *itf_desc, uint16_t max_len) {
+static uint16_t pl2303_open(uint8_t daddr, const tusb_desc_interface_t *itf_desc, uint16_t max_len) {
   // PL2303 Interface includes 1 vendor interface + 1 interrupt endpoints + 2 bulk
-  TU_VERIFY(itf_desc->bNumEndpoints == 3);
-  TU_VERIFY(sizeof(tusb_desc_interface_t) + 3 * sizeof(tusb_desc_endpoint_t) <= max_len);
+  TU_VERIFY(itf_desc->bNumEndpoints == 3, 0);
+  const uint16_t drv_len =
+    (uint16_t)(sizeof(tusb_desc_interface_t) + itf_desc->bNumEndpoints * sizeof(tusb_desc_endpoint_t));
+  TU_VERIFY(drv_len <= max_len, 0);
 
   cdch_interface_t *p_cdc = make_new_itf(daddr, itf_desc);
-  TU_VERIFY(p_cdc);
+  TU_VERIFY(p_cdc, 0);
 
   p_cdc->serial_drid = SERIAL_DRIVER_PL2303;
   p_cdc->pl2303.quirks = 0;
@@ -2103,23 +2113,21 @@ static bool pl2303_open(uint8_t daddr, tusb_desc_interface_t const *itf_desc, ui
   tusb_desc_endpoint_t const *desc_ep = (tusb_desc_endpoint_t const *) tu_desc_next(itf_desc);
 
   // Interrupt endpoint: not used for now
-  TU_ASSERT(TUSB_DESC_ENDPOINT == tu_desc_type(desc_ep) &&
-            TUSB_XFER_INTERRUPT == desc_ep->bmAttributes.xfer);
-  TU_ASSERT(tuh_edpt_open(daddr, desc_ep));
+  TU_ASSERT(TUSB_DESC_ENDPOINT == tu_desc_type(desc_ep) && TUSB_XFER_INTERRUPT == desc_ep->bmAttributes.xfer, 0);
+  TU_ASSERT(tuh_edpt_open(daddr, desc_ep), 0);
   p_cdc->ep_notif = desc_ep->bEndpointAddress;
   desc_ep += 1;
 
   // data endpoints expected to be in pairs
-  TU_ASSERT(open_ep_stream_pair(p_cdc, desc_ep));
+  TU_ASSERT(open_ep_stream_pair(p_cdc, desc_ep), 0);
 
-  return true;
+  return drv_len;
 }
 
 static bool pl2303_process_set_config(cdch_interface_t *p_cdc, tuh_xfer_t *xfer) {
   // state CONFIG_PL2303_READ1 may have no success due to expected stall by pl2303_supports_hx_status()
   const uintptr_t state = xfer->user_data;
   TU_ASSERT(xfer->result == XFER_RESULT_SUCCESS || state == CONFIG_PL2303_READ1);
-  uint8_t* enum_buf = usbh_get_enum_buf();
   pl2303_type_t type;
 
   switch (state) {
@@ -2131,10 +2139,9 @@ static bool pl2303_process_set_config(cdch_interface_t *p_cdc, tuh_xfer_t *xfer)
       if (type == PL2303_TYPE_NEED_SUPPORTS_HX_STATUS) {
         TU_ASSERT(pl2303_supports_hx_status(p_cdc, cdch_process_set_config, CONFIG_PL2303_READ1));
         break;
-      } else {
-        // no transfer triggered and continue with CONFIG_PL2303_READ1
-        TU_ATTR_FALLTHROUGH;
       }
+      // no transfer triggered and continue with CONFIG_PL2303_READ1
+      TU_ATTR_FALLTHROUGH;
 
     case CONFIG_PL2303_READ1:
       // get supports_hx_status, type and quirks (step 2), do special read
@@ -2151,7 +2158,7 @@ static bool pl2303_process_set_config(cdch_interface_t *p_cdc, tuh_xfer_t *xfer)
 
       // purpose unknown, overtaken from Linux Kernel driver
       if (p_cdc->pl2303.type != PL2303_TYPE_HXN) {
-        TU_ASSERT(pl2303_vendor_read(p_cdc, 0x8484, enum_buf, cdch_process_set_config, CONFIG_PL2303_WRITE1));
+        TU_ASSERT(pl2303_vendor_read(p_cdc, 0x8484, cdch_process_set_config, CONFIG_PL2303_WRITE1));
         break;
       }// else: continue with next step
       TU_ATTR_FALLTHROUGH;
@@ -2167,7 +2174,7 @@ static bool pl2303_process_set_config(cdch_interface_t *p_cdc, tuh_xfer_t *xfer)
     case CONFIG_PL2303_READ2:
       // purpose unknown, overtaken from Linux Kernel driver
       if (p_cdc->pl2303.type != PL2303_TYPE_HXN) {
-        TU_ASSERT(pl2303_vendor_read(p_cdc, 0x8484, enum_buf, cdch_process_set_config, CONFIG_PL2303_READ3));
+        TU_ASSERT(pl2303_vendor_read(p_cdc, 0x8484, cdch_process_set_config, CONFIG_PL2303_READ3));
         break;
       }// else: continue with next step
       TU_ATTR_FALLTHROUGH;
@@ -2175,7 +2182,7 @@ static bool pl2303_process_set_config(cdch_interface_t *p_cdc, tuh_xfer_t *xfer)
     case CONFIG_PL2303_READ3:
       // purpose unknown, overtaken from Linux Kernel driver
       if (p_cdc->pl2303.type != PL2303_TYPE_HXN) {
-        TU_ASSERT(pl2303_vendor_read(p_cdc, 0x8383, enum_buf, cdch_process_set_config, CONFIG_PL2303_READ4));
+        TU_ASSERT(pl2303_vendor_read(p_cdc, 0x8383, cdch_process_set_config, CONFIG_PL2303_READ4));
         break;
       }// else: continue with next step
       TU_ATTR_FALLTHROUGH;
@@ -2183,7 +2190,7 @@ static bool pl2303_process_set_config(cdch_interface_t *p_cdc, tuh_xfer_t *xfer)
     case CONFIG_PL2303_READ4:
       // purpose unknown, overtaken from Linux Kernel driver
       if (p_cdc->pl2303.type != PL2303_TYPE_HXN) {
-        TU_ASSERT(pl2303_vendor_read(p_cdc, 0x8484, enum_buf, cdch_process_set_config, CONFIG_PL2303_WRITE2));
+        TU_ASSERT(pl2303_vendor_read(p_cdc, 0x8484, cdch_process_set_config, CONFIG_PL2303_WRITE2));
         break;
       }// else: continue with next step
       TU_ATTR_FALLTHROUGH;
@@ -2199,7 +2206,7 @@ static bool pl2303_process_set_config(cdch_interface_t *p_cdc, tuh_xfer_t *xfer)
     case CONFIG_PL2303_READ5:
       // purpose unknown, overtaken from Linux Kernel driver
       if (p_cdc->pl2303.type != PL2303_TYPE_HXN) {
-        TU_ASSERT(pl2303_vendor_read(p_cdc, 0x8484, enum_buf, cdch_process_set_config, CONFIG_PL2303_READ6));
+        TU_ASSERT(pl2303_vendor_read(p_cdc, 0x8484, cdch_process_set_config, CONFIG_PL2303_READ6));
         break;
       }// else: continue with next step
       TU_ATTR_FALLTHROUGH;
@@ -2207,7 +2214,7 @@ static bool pl2303_process_set_config(cdch_interface_t *p_cdc, tuh_xfer_t *xfer)
     case CONFIG_PL2303_READ6:
       // purpose unknown, overtaken from Linux Kernel driver
       if (p_cdc->pl2303.type != PL2303_TYPE_HXN) {
-        TU_ASSERT(pl2303_vendor_read(p_cdc, 0x8383, enum_buf, cdch_process_set_config, CONFIG_PL2303_WRITE3));
+        TU_ASSERT(pl2303_vendor_read(p_cdc, 0x8383, cdch_process_set_config, CONFIG_PL2303_WRITE3));
         break;
       }// else: continue with next step
       TU_ATTR_FALLTHROUGH;
@@ -2379,10 +2386,12 @@ static pl2303_type_t pl2303_detect_type(cdch_interface_t *p_cdc, uint8_t step) {
           return PL2303_TYPE_HXN;
 
         default:
-          break;
+          break; // unknown device
       }
       break;
-    default: break;
+
+    default:
+      break; // unknown device
   }
 
   TU_LOG_CDC(p_cdc, "unknown device type bcdUSB = 0x%04x", desc_dev.bcdUSB);
@@ -2444,8 +2453,9 @@ static uint32_t pl2303_encode_baud_rate_divisor(uint8_t buf[PL2303_LINE_CODING_B
    */
   baseline = 12000000 * 32;
   mantissa = baseline / baud;
-  if (mantissa == 0)
+  if (mantissa == 0) {
     mantissa = 1; /* Avoid dividing by zero if baud > 32 * 12M. */
+  }
   exponent = 0;
   while (mantissa >= 512) {
     if (exponent < 7) {
@@ -2517,7 +2527,7 @@ static bool pl2303_encode_baud_rate(cdch_interface_t *p_cdc, uint8_t buf[PL2303_
    * Use direct method for supported baud rates, otherwise use divisors.
    * Newer chip types do not support divisor encoding.
    */
-  if (type_data->no_divisors) {
+  if (type_data->no_divisors != 0) {
     baud_sup = baud;
   } else {
     baud_sup = pl2303_get_supported_baud_rate(baud);
@@ -2525,7 +2535,7 @@ static bool pl2303_encode_baud_rate(cdch_interface_t *p_cdc, uint8_t buf[PL2303_
 
   if (baud == baud_sup) {
     baud = pl2303_encode_baud_rate_direct(buf, baud);
-  } else if (type_data->alt_divisors) {
+  } else if (type_data->alt_divisors != 0) {
     baud = pl2303_encode_baud_rate_divisor_alt(buf, baud);
   } else {
     baud = pl2303_encode_baud_rate_divisor(buf, baud);