2 files changed, 185 insertions, 257 deletions

diff --git a/src/class/cdc/cdc_device.c b/src/class/cdc/cdc_device.c
index bf631908f..9e62c6509 100644
--- a/src/class/cdc/cdc_device.c
+++ b/src/class/cdc/cdc_device.c
@@ -48,28 +48,23 @@
 typedef struct {
   uint8_t rhport;
   uint8_t itf_num;
-  uint8_t ep_in;
-  uint8_t ep_out;
-
   uint8_t ep_notify;
   uint8_t line_state; // Bit 0: DTR, Bit 1: RTS
 
   /*------------- From this point, data is not cleared by bus reset -------------*/
-  char wanted_char;
   TU_ATTR_ALIGNED(4) cdc_line_coding_t line_coding;
+  char wanted_char;
 
-  // FIFO
-  tu_fifo_t rx_ff;
-  tu_fifo_t tx_ff;
-
-  uint8_t rx_ff_buf[CFG_TUD_CDC_RX_BUFSIZE];
-  uint8_t tx_ff_buf[CFG_TUD_CDC_TX_BUFSIZE];
+  struct {
+    tu_edpt_stream_t tx;
+    tu_edpt_stream_t rx;
 
-  OSAL_MUTEX_DEF(rx_ff_mutex);
-  OSAL_MUTEX_DEF(tx_ff_mutex);
+    uint8_t tx_ff_buf[CFG_TUD_CDC_TX_BUFSIZE];
+    uint8_t rx_ff_buf[CFG_TUD_CDC_RX_BUFSIZE];
+  } stream;
 } cdcd_interface_t;
 
-#define ITF_MEM_RESET_SIZE   offsetof(cdcd_interface_t, wanted_char)
+#define ITF_MEM_RESET_SIZE offsetof(cdcd_interface_t, line_coding)
 
 typedef struct {
   TUD_EPBUF_DEF(epout, CFG_TUD_CDC_EP_BUFSIZE);
@@ -81,110 +76,100 @@ typedef struct {
 } cdcd_epbuf_t;
 
 //--------------------------------------------------------------------+
-// INTERNAL OBJECT & FUNCTION DECLARATION
-//--------------------------------------------------------------------+
-static cdcd_interface_t _cdcd_itf[CFG_TUD_CDC];
-CFG_TUD_MEM_SECTION static cdcd_epbuf_t _cdcd_epbuf[CFG_TUD_CDC];
-
-static tud_cdc_configure_t _cdcd_cfg = TUD_CDC_CONFIGURE_DEFAULT();
-
-static bool _prep_out_transaction(uint8_t itf) {
-  const uint8_t rhport = 0;
-  cdcd_interface_t* p_cdc = &_cdcd_itf[itf];
-  cdcd_epbuf_t* p_epbuf = &_cdcd_epbuf[itf];
-
-  // Skip if usb is not ready yet
-  TU_VERIFY(tud_ready() && p_cdc->ep_out);
-
-  uint16_t available = tu_fifo_remaining(&p_cdc->rx_ff);
-
-  // Prepare for incoming data but only allow what we can store in the ring buffer.
-  // TODO Actually we can still carry out the transfer, keeping count of received bytes
-  // and slowly move it to the FIFO when read().
-  // This pre-check reduces endpoint claiming
-  TU_VERIFY(available >= CFG_TUD_CDC_EP_BUFSIZE);
-
-  // claim endpoint
-  TU_VERIFY(usbd_edpt_claim(p_cdc->rhport, p_cdc->ep_out));
-
-  // fifo can be changed before endpoint is claimed
-  available = tu_fifo_remaining(&p_cdc->rx_ff);
-
-  if (available >= CFG_TUD_CDC_EP_BUFSIZE) {
-    return usbd_edpt_xfer(rhport, p_cdc->ep_out, p_epbuf->epout, CFG_TUD_CDC_EP_BUFSIZE, false);
-  } else {
-    // Release endpoint since we don't make any transfer
-    usbd_edpt_release(p_cdc->rhport, p_cdc->ep_out);
-    return false;
-  }
-}
-
-//--------------------------------------------------------------------+
 // Weak stubs: invoked if no strong implementation is available
 //--------------------------------------------------------------------+
 TU_ATTR_WEAK void tud_cdc_rx_cb(uint8_t itf) {
-  (void) itf;
+  (void)itf;
 }
 
 TU_ATTR_WEAK void tud_cdc_rx_wanted_cb(uint8_t itf, char wanted_char) {
-  (void) itf;
-  (void) wanted_char;
+  (void)itf;
+  (void)wanted_char;
 }
 
 TU_ATTR_WEAK void tud_cdc_tx_complete_cb(uint8_t itf) {
-  (void) itf;
+  (void)itf;
 }
 
 TU_ATTR_WEAK void tud_cdc_notify_complete_cb(uint8_t itf) {
-  (void) itf;
+  (void)itf;
 }
 
 TU_ATTR_WEAK void tud_cdc_line_state_cb(uint8_t itf, bool dtr, bool rts) {
-  (void) itf;
-  (void) dtr;
-  (void) rts;
+  (void)itf;
+  (void)dtr;
+  (void)rts;
 }
 
-TU_ATTR_WEAK void tud_cdc_line_coding_cb(uint8_t itf, cdc_line_coding_t const* p_line_coding) {
-  (void) itf;
-  (void) p_line_coding;
+TU_ATTR_WEAK void tud_cdc_line_coding_cb(uint8_t itf, const cdc_line_coding_t *p_line_coding) {
+  (void)itf;
+  (void)p_line_coding;
 }
 
 TU_ATTR_WEAK void tud_cdc_send_break_cb(uint8_t itf, uint16_t duration_ms) {
-  (void) itf;
-  (void) duration_ms;
+  (void)itf;
+  (void)duration_ms;
+}
+
+//--------------------------------------------------------------------+
+// INTERNAL OBJECT & FUNCTION DECLARATION
+//--------------------------------------------------------------------+
+static cdcd_interface_t _cdcd_itf[CFG_TUD_CDC];
+CFG_TUD_MEM_SECTION static cdcd_epbuf_t _cdcd_epbuf[CFG_TUD_CDC];
+static tud_cdc_configure_t _cdcd_cfg = TUD_CDC_CONFIGURE_DEFAULT();
+
+TU_ATTR_ALWAYS_INLINE static inline uint8_t find_cdc_itf(uint8_t ep_addr) {
+  for (uint8_t idx = 0; idx < CFG_TUD_CDC; idx++) {
+    const cdcd_interface_t *p_cdc = &_cdcd_itf[idx];
+    if (ep_addr == p_cdc->stream.rx.ep_addr || ep_addr == p_cdc->stream.tx.ep_addr ||
+        (ep_addr == p_cdc->ep_notify && ep_addr != 0)) {
+      return idx;
+    }
+  }
+  return TUSB_INDEX_INVALID_8;
 }
 
 //--------------------------------------------------------------------+
 // APPLICATION API
 //--------------------------------------------------------------------+
 bool tud_cdc_configure(const tud_cdc_configure_t* driver_cfg) {
-  TU_VERIFY(driver_cfg);
+  TU_VERIFY(driver_cfg != NULL);
   _cdcd_cfg = *driver_cfg;
   return true;
 }
 
 bool tud_cdc_n_ready(uint8_t itf) {
-  return tud_ready() && _cdcd_itf[itf].ep_in != 0 && _cdcd_itf[itf].ep_out != 0;
+  TU_VERIFY(itf < CFG_TUD_CDC);
+  TU_VERIFY(tud_ready());
+  const cdcd_interface_t *p_cdc = &_cdcd_itf[itf];
+
+  const bool in_opened  = tu_edpt_stream_is_opened(&p_cdc->stream.tx);
+  const bool out_opened = tu_edpt_stream_is_opened(&p_cdc->stream.rx);
+  return in_opened && out_opened;
 }
 
 bool tud_cdc_n_connected(uint8_t itf) {
+  TU_VERIFY(itf < CFG_TUD_CDC);
+  TU_VERIFY(tud_ready());
   // DTR (bit 0) active  is considered as connected
-  return tud_ready() && tu_bit_test(_cdcd_itf[itf].line_state, 0);
+  return tu_bit_test(_cdcd_itf[itf].line_state, 0);
 }
 
 uint8_t tud_cdc_n_get_line_state(uint8_t itf) {
+  TU_VERIFY(itf < CFG_TUD_CDC, 0);
   return _cdcd_itf[itf].line_state;
 }
 
-void tud_cdc_n_get_line_coding(uint8_t itf, cdc_line_coding_t* coding) {
+void tud_cdc_n_get_line_coding(uint8_t itf, cdc_line_coding_t *coding) {
+  TU_VERIFY(itf < CFG_TUD_CDC, );
   (*coding) = _cdcd_itf[itf].line_coding;
 }
 
 #if CFG_TUD_CDC_NOTIFY
 bool tud_cdc_n_notify_uart_state (uint8_t itf, const cdc_notify_uart_state_t *state) {
-  cdcd_interface_t* p_cdc = &_cdcd_itf[itf];
-  cdcd_epbuf_t* p_epbuf = &_cdcd_epbuf[itf];
+  TU_VERIFY(itf < CFG_TUD_CDC);
+  cdcd_interface_t *p_cdc   = &_cdcd_itf[itf];
+  cdcd_epbuf_t     *p_epbuf = &_cdcd_epbuf[itf];
   TU_VERIFY(tud_ready() && p_cdc->ep_notify != 0);
   TU_VERIFY(usbd_edpt_claim(p_cdc->rhport, p_cdc->ep_notify));
 
@@ -200,8 +185,9 @@ bool tud_cdc_n_notify_uart_state (uint8_t itf, const cdc_notify_uart_state_t *st
 }
 
 bool tud_cdc_n_notify_conn_speed_change(uint8_t itf, const cdc_notify_conn_speed_change_t* conn_speed_change) {
-  cdcd_interface_t* p_cdc = &_cdcd_itf[itf];
-  cdcd_epbuf_t* p_epbuf = &_cdcd_epbuf[itf];
+  TU_VERIFY(itf < CFG_TUD_CDC);
+  cdcd_interface_t *p_cdc   = &_cdcd_itf[itf];
+  cdcd_epbuf_t     *p_epbuf = &_cdcd_epbuf[itf];
   TU_VERIFY(tud_ready() && p_cdc->ep_notify != 0);
   TU_VERIFY(usbd_edpt_claim(p_cdc->rhport, p_cdc->ep_notify));
 
@@ -218,6 +204,7 @@ bool tud_cdc_n_notify_conn_speed_change(uint8_t itf, const cdc_notify_conn_speed
 #endif
 
 void tud_cdc_n_set_wanted_char(uint8_t itf, char wanted) {
+  TU_VERIFY(itf < CFG_TUD_CDC, );
   _cdcd_itf[itf].wanted_char = wanted;
 }
 
@@ -225,77 +212,53 @@ void tud_cdc_n_set_wanted_char(uint8_t itf, char wanted) {
 // READ API
 //--------------------------------------------------------------------+
 uint32_t tud_cdc_n_available(uint8_t itf) {
-  return tu_fifo_count(&_cdcd_itf[itf].rx_ff);
+  TU_VERIFY(itf < CFG_TUD_CDC, 0);
+  return tu_edpt_stream_read_available(&_cdcd_itf[itf].stream.rx);
 }
 
 uint32_t tud_cdc_n_read(uint8_t itf, void* buffer, uint32_t bufsize) {
-  cdcd_interface_t* p_cdc = &_cdcd_itf[itf];
-  uint32_t num_read = tu_fifo_read_n(&p_cdc->rx_ff, buffer, (uint16_t) TU_MIN(bufsize, UINT16_MAX));
-  _prep_out_transaction(itf);
-  return num_read;
+  TU_VERIFY(itf < CFG_TUD_CDC, 0);
+  cdcd_interface_t *p_cdc = &_cdcd_itf[itf];
+  return tu_edpt_stream_read(p_cdc->rhport, &p_cdc->stream.rx, buffer, bufsize);
 }
 
-bool tud_cdc_n_peek(uint8_t itf, uint8_t* chr) {
-  return tu_fifo_peek(&_cdcd_itf[itf].rx_ff, chr);
+bool tud_cdc_n_peek(uint8_t itf, uint8_t *chr) {
+  TU_VERIFY(itf < CFG_TUD_CDC);
+  return tu_edpt_stream_peek(&_cdcd_itf[itf].stream.rx, chr);
 }
 
 void tud_cdc_n_read_flush(uint8_t itf) {
-  cdcd_interface_t* p_cdc = &_cdcd_itf[itf];
-  tu_fifo_clear(&p_cdc->rx_ff);
-  _prep_out_transaction(itf);
+  TU_VERIFY(itf < CFG_TUD_CDC, );
+  cdcd_interface_t *p_cdc = &_cdcd_itf[itf];
+  tu_edpt_stream_clear(&p_cdc->stream.rx);
+  tu_edpt_stream_read_xfer(p_cdc->rhport, &p_cdc->stream.rx);
 }
 
 //--------------------------------------------------------------------+
 // WRITE API
 //--------------------------------------------------------------------+
 uint32_t tud_cdc_n_write(uint8_t itf, const void* buffer, uint32_t bufsize) {
-  cdcd_interface_t* p_cdc = &_cdcd_itf[itf];
-  uint16_t wr_count = tu_fifo_write_n(&p_cdc->tx_ff, buffer, (uint16_t) TU_MIN(bufsize, UINT16_MAX));
-
-  // flush if queue more than packet size
-  if (tu_fifo_count(&p_cdc->tx_ff) >= BULK_PACKET_SIZE
-      #if CFG_TUD_CDC_TX_BUFSIZE < BULK_PACKET_SIZE
-      || tu_fifo_full(&p_cdc->tx_ff) // check full if fifo size is less than packet size
-      #endif
-      ) {
-    tud_cdc_n_write_flush(itf);
-  }
-
-  return wr_count;
+  TU_VERIFY(itf < CFG_TUD_CDC, 0);
+  cdcd_interface_t *p_cdc = &_cdcd_itf[itf];
+  return tu_edpt_stream_write(p_cdc->rhport, &p_cdc->stream.tx, buffer, bufsize);
 }
 
 uint32_t tud_cdc_n_write_flush(uint8_t itf) {
-  cdcd_interface_t* p_cdc = &_cdcd_itf[itf];
-  cdcd_epbuf_t* p_epbuf = &_cdcd_epbuf[itf];
-  TU_VERIFY(tud_ready(), 0); // Skip if usb is not ready yet
-
-  // No data to send
-  if (0 == tu_fifo_count(&p_cdc->tx_ff)) {
-    return 0;
-  }
-
-  TU_VERIFY(usbd_edpt_claim(p_cdc->rhport, p_cdc->ep_in), 0); // Claim the endpoint
-
-  // Pull data from FIFO
-  const uint16_t count = tu_fifo_read_n(&p_cdc->tx_ff, p_epbuf->epin, CFG_TUD_CDC_EP_BUFSIZE);
-
-  if (count > 0) {
-    TU_ASSERT(usbd_edpt_xfer(p_cdc->rhport, p_cdc->ep_in, p_epbuf->epin, count, false), 0);
-    return count;
-  } else {
-    // Release endpoint since we don't make any transfer
-    // Note: data is dropped if terminal is not connected
-    usbd_edpt_release(p_cdc->rhport, p_cdc->ep_in);
-    return 0;
-  }
+  TU_VERIFY(itf < CFG_TUD_CDC, 0);
+  cdcd_interface_t *p_cdc = &_cdcd_itf[itf];
+  return tu_edpt_stream_write_xfer(p_cdc->rhport, &p_cdc->stream.tx);
 }
 
 uint32_t tud_cdc_n_write_available(uint8_t itf) {
-  return tu_fifo_remaining(&_cdcd_itf[itf].tx_ff);
+  TU_VERIFY(itf < CFG_TUD_CDC, 0);
+  cdcd_interface_t *p_cdc = &_cdcd_itf[itf];
+  return tu_edpt_stream_write_available(p_cdc->rhport, &p_cdc->stream.tx);
 }
 
 bool tud_cdc_n_write_clear(uint8_t itf) {
-  return tu_fifo_clear(&_cdcd_itf[itf].tx_ff);
+  TU_VERIFY(itf < CFG_TUD_CDC);
+  cdcd_interface_t *p_cdc = &_cdcd_itf[itf];
+  return tu_edpt_stream_clear(&p_cdc->stream.tx);
 }
 
 //--------------------------------------------------------------------+
@@ -304,7 +267,8 @@ bool tud_cdc_n_write_clear(uint8_t itf) {
 void cdcd_init(void) {
   tu_memclr(_cdcd_itf, sizeof(_cdcd_itf));
   for (uint8_t i = 0; i < CFG_TUD_CDC; i++) {
-    cdcd_interface_t* p_cdc = &_cdcd_itf[i];
+    cdcd_interface_t *p_cdc   = &_cdcd_itf[i];
+    cdcd_epbuf_t     *p_epbuf = &_cdcd_epbuf[i];
 
     p_cdc->wanted_char = (char) -1;
 
@@ -314,44 +278,23 @@ void cdcd_init(void) {
     p_cdc->line_coding.parity = 0;
     p_cdc->line_coding.data_bits = 8;
 
-    // Config RX fifo
-    tu_fifo_config(&p_cdc->rx_ff, p_cdc->rx_ff_buf, TU_ARRAY_SIZE(p_cdc->rx_ff_buf), 1, false);
+    tu_edpt_stream_init(&p_cdc->stream.rx, false, false, false, p_cdc->stream.rx_ff_buf, CFG_TUD_CDC_RX_BUFSIZE,
+                        p_epbuf->epout, CFG_TUD_CDC_EP_BUFSIZE);
 
     // TX fifo can be configured to change to overwritable if not connected (DTR bit not set). Without DTR we do not
     // know if data is actually polled by terminal. This way the most current data is prioritized.
     // Default: is overwritable
-    tu_fifo_config(&p_cdc->tx_ff, p_cdc->tx_ff_buf, TU_ARRAY_SIZE(p_cdc->tx_ff_buf), 1, _cdcd_cfg.tx_overwritabe_if_not_connected);
-
-    #if OSAL_MUTEX_REQUIRED
-    osal_mutex_t mutex_rd = osal_mutex_create(&p_cdc->rx_ff_mutex);
-    osal_mutex_t mutex_wr = osal_mutex_create(&p_cdc->tx_ff_mutex);
-    TU_ASSERT(mutex_rd != NULL && mutex_wr != NULL, );
-
-    tu_fifo_config_mutex(&p_cdc->rx_ff, NULL, mutex_rd);
-    tu_fifo_config_mutex(&p_cdc->tx_ff, mutex_wr, NULL);
-    #endif
+    tu_edpt_stream_init(&p_cdc->stream.tx, false, true, _cdcd_cfg.tx_overwritabe_if_not_connected,
+                        p_cdc->stream.tx_ff_buf, CFG_TUD_CDC_TX_BUFSIZE, p_epbuf->epin, CFG_TUD_CDC_EP_BUFSIZE);
   }
 }
 
 bool cdcd_deinit(void) {
-  #if OSAL_MUTEX_REQUIRED
-  for(uint8_t i=0; i<CFG_TUD_CDC; i++) {
+  for (uint8_t i = 0; i < CFG_TUD_CDC; i++) {
     cdcd_interface_t* p_cdc = &_cdcd_itf[i];
-    const osal_mutex_t mutex_rd = p_cdc->rx_ff.mutex_rd;
-    const osal_mutex_t mutex_wr = p_cdc->tx_ff.mutex_wr;
-
-    if (mutex_rd != NULL) {
-      osal_mutex_delete(mutex_rd);
-      tu_fifo_config_mutex(&p_cdc->rx_ff, NULL, NULL);
-    }
-
-    if (mutex_wr != NULL) {
-      osal_mutex_delete(mutex_wr);
-      tu_fifo_config_mutex(&p_cdc->tx_ff, NULL, NULL);
-    }
+    tu_edpt_stream_deinit(&p_cdc->stream.rx);
+    tu_edpt_stream_deinit(&p_cdc->stream.tx);
   }
-  #endif
-
   return true;
 }
 
@@ -360,74 +303,85 @@ void cdcd_reset(uint8_t rhport) {
 
   for (uint8_t i = 0; i < CFG_TUD_CDC; i++) {
     cdcd_interface_t* p_cdc = &_cdcd_itf[i];
-
     tu_memclr(p_cdc, ITF_MEM_RESET_SIZE);
-    if (!_cdcd_cfg.rx_persistent) {
-      tu_fifo_clear(&p_cdc->rx_ff);
-    }
-    if (!_cdcd_cfg.tx_persistent) {
-      tu_fifo_clear(&p_cdc->tx_ff);
-    }
-    tu_fifo_set_overwritable(&p_cdc->tx_ff, _cdcd_cfg.tx_overwritabe_if_not_connected);
+
+    tu_fifo_set_overwritable(&p_cdc->stream.tx.ff, _cdcd_cfg.tx_overwritabe_if_not_connected); // back to default
+    tu_edpt_stream_close(&p_cdc->stream.rx);
+    tu_edpt_stream_close(&p_cdc->stream.tx);
   }
 }
 
 uint16_t cdcd_open(uint8_t rhport, const tusb_desc_interface_t* itf_desc, uint16_t max_len) {
   // Only support ACM subclass
-  TU_VERIFY( TUSB_CLASS_CDC                           == itf_desc->bInterfaceClass &&
-             CDC_COMM_SUBCLASS_ABSTRACT_CONTROL_MODEL == itf_desc->bInterfaceSubClass, 0);
+  TU_VERIFY(TUSB_CLASS_CDC == itf_desc->bInterfaceClass &&
+              CDC_COMM_SUBCLASS_ABSTRACT_CONTROL_MODEL == itf_desc->bInterfaceSubClass,
+            0);
 
-  // Find available interface
-  cdcd_interface_t* p_cdc;
-  uint8_t cdc_id;
-  for (cdc_id = 0; cdc_id < CFG_TUD_CDC; cdc_id++) {
-    p_cdc = &_cdcd_itf[cdc_id];
-    if (p_cdc->ep_in == 0) {
-      break;
-    }
-  }
+  const uint8_t cdc_id = find_cdc_itf(0); // Find available interface
   TU_ASSERT(cdc_id < CFG_TUD_CDC, 0);
+  cdcd_interface_t *p_cdc = &_cdcd_itf[cdc_id];
 
   //------------- Control Interface -------------//
   p_cdc->rhport = rhport;
   p_cdc->itf_num = itf_desc->bInterfaceNumber;
 
-  uint16_t drv_len = sizeof(tusb_desc_interface_t);
-  const uint8_t* p_desc = tu_desc_next(itf_desc);
+  const uint8_t *p_desc   = (const uint8_t *)itf_desc;
+  const uint8_t *desc_end = p_desc + max_len;
 
-  // Communication Functional Descriptors
-  while (TUSB_DESC_CS_INTERFACE == tu_desc_type(p_desc) && drv_len <= max_len) {
-    drv_len += tu_desc_len(p_desc);
+  // Skip all class-specific descriptor
+  p_desc = tu_desc_next(itf_desc);
+  while (tu_desc_in_bounds(p_desc, desc_end) && TUSB_DESC_CS_INTERFACE == tu_desc_type(p_desc)) {
     p_desc = tu_desc_next(p_desc);
   }
 
+  // notification endpoint (optional)
   if (TUSB_DESC_ENDPOINT == tu_desc_type(p_desc)) {
-    // notification endpoint
     const tusb_desc_endpoint_t* desc_ep = (const tusb_desc_endpoint_t*) p_desc;
     TU_ASSERT(usbd_edpt_open(rhport, desc_ep), 0);
     p_cdc->ep_notify = desc_ep->bEndpointAddress;
 
-    drv_len += tu_desc_len(p_desc);
     p_desc = tu_desc_next(p_desc);
   }
 
-  //------------- Data Interface (if any) -------------//
-  if ((TUSB_DESC_INTERFACE == tu_desc_type(p_desc)) &&
-      (TUSB_CLASS_CDC_DATA == ((const tusb_desc_interface_t*) p_desc)->bInterfaceClass)) {
-    // next to endpoint descriptor
-    drv_len += tu_desc_len(p_desc);
-    p_desc = tu_desc_next(p_desc);
+  //------------- Data Interface (optional) -------------//
+  if (TUSB_DESC_INTERFACE == tu_desc_type(p_desc)) {
+    const tusb_desc_interface_t *data_itf_desc = (const tusb_desc_interface_t *)p_desc;
+    if (TUSB_CLASS_CDC_DATA == data_itf_desc->bInterfaceClass) {
+      for (uint8_t e = 0; e < data_itf_desc->bNumEndpoints; e++) {
+        if (!tu_desc_in_bounds(p_desc, desc_end)) {
+          break;
+        }
+        p_desc = tu_desc_next(p_desc);
 
-    // Open endpoint pair
-    TU_ASSERT(usbd_open_edpt_pair(rhport, p_desc, 2, TUSB_XFER_BULK, &p_cdc->ep_out, &p_cdc->ep_in), 0);
+        const tusb_desc_endpoint_t *desc_ep = (const tusb_desc_endpoint_t *)p_desc;
+        TU_ASSERT(TUSB_DESC_ENDPOINT == desc_ep->bDescriptorType && TUSB_XFER_BULK == desc_ep->bmAttributes.xfer, 0);
 
-    drv_len += 2 * sizeof(tusb_desc_endpoint_t);
-  }
+        TU_ASSERT(usbd_edpt_open(rhport, desc_ep), 0);
+        if (tu_edpt_dir(desc_ep->bEndpointAddress) == TUSB_DIR_IN) {
+          tu_edpt_stream_t *stream_tx = &p_cdc->stream.tx;
+
+          tu_edpt_stream_open(stream_tx, desc_ep);
+          if (_cdcd_cfg.tx_persistent) {
+            tu_edpt_stream_write_xfer(rhport, stream_tx); // flush pending data
+          } else {
+            tu_edpt_stream_clear(stream_tx);
+          }
+        } else {
+          tu_edpt_stream_t *stream_rx = &p_cdc->stream.rx;
 
-  // Prepare for incoming data
-  _prep_out_transaction(cdc_id);
+          tu_edpt_stream_open(stream_rx, desc_ep);
+          if (!_cdcd_cfg.rx_persistent) {
+            tu_edpt_stream_clear(stream_rx);
+          }
+          TU_ASSERT(tu_edpt_stream_read_xfer(rhport, stream_rx) > 0, 0); // prepare for incoming data
+        }
+      }
 
-  return drv_len;
+      p_desc = tu_desc_next(p_desc);
+    }
+  }
+
+  return (uint16_t)(p_desc - (const uint8_t *)itf_desc);
 }
 
 // Invoked when a control transfer occurred on an interface of this class
@@ -449,7 +403,7 @@ bool cdcd_control_xfer_cb(uint8_t rhport, uint8_t stage, const tusb_control_requ
   }
   TU_VERIFY(itf < CFG_TUD_CDC);
 
-  switch (request->bRequest) { //-V2520 //-V2659
+  switch (request->bRequest) {
     case CDC_REQUEST_SET_LINE_CODING:
       if (stage == CONTROL_STAGE_SETUP) {
         TU_LOG_DRV("  Set Line Coding\r\n");
@@ -484,15 +438,13 @@ bool cdcd_control_xfer_cb(uint8_t rhport, uint8_t stage, const tusb_control_requ
 
         // If enabled: fifo overwriting is disabled if DTR bit is set and vice versa
         if (_cdcd_cfg.tx_overwritabe_if_not_connected) {
-          tu_fifo_set_overwritable(&p_cdc->tx_ff, !dtr);
+          tu_fifo_set_overwritable(&p_cdc->stream.tx.ff, !dtr);
         } else {
-          tu_fifo_set_overwritable(&p_cdc->tx_ff, false);
+          tu_fifo_set_overwritable(&p_cdc->stream.tx.ff, false);
         }
 
         TU_LOG_DRV("  Set Control Line State: DTR = %d, RTS = %d\r\n", dtr, rts);
-
-        // Invoke callback
-        tud_cdc_line_state_cb(itf, dtr, rts);
+        tud_cdc_line_state_cb(itf, dtr, rts); // invoke callback
       } else {
         // nothing to do
       }
@@ -507,7 +459,6 @@ bool cdcd_control_xfer_cb(uint8_t rhport, uint8_t stage, const tusb_control_requ
       } else {
         // nothing to do
       }
-
       break;
 
     default:
@@ -518,58 +469,45 @@ bool cdcd_control_xfer_cb(uint8_t rhport, uint8_t stage, const tusb_control_requ
 }
 
 bool cdcd_xfer_cb(uint8_t rhport, uint8_t ep_addr, xfer_result_t result, uint32_t xferred_bytes) {
-  (void) result;
+  (void)result;
 
-  uint8_t itf;
-  cdcd_interface_t* p_cdc;
-
-  // Identify which interface to use
-  for (itf = 0; itf < CFG_TUD_CDC; itf++) {
-    p_cdc = &_cdcd_itf[itf];
-    if ((ep_addr == p_cdc->ep_out) || (ep_addr == p_cdc->ep_in) || (ep_addr == p_cdc->ep_notify)) {
-      break;
-    }
-  }
+  uint8_t itf = find_cdc_itf(ep_addr);
   TU_ASSERT(itf < CFG_TUD_CDC);
-  cdcd_epbuf_t* p_epbuf = &_cdcd_epbuf[itf];
+  cdcd_interface_t *p_cdc     = &_cdcd_itf[itf];
+  tu_edpt_stream_t *stream_rx = &p_cdc->stream.rx;
+  tu_edpt_stream_t *stream_tx = &p_cdc->stream.tx;
 
-  // Received new data
-  if (ep_addr == p_cdc->ep_out) {
-    tu_fifo_write_n(&p_cdc->rx_ff, p_epbuf->epout, (uint16_t) xferred_bytes);
+  // Received new data, move to fifo
+  if (ep_addr == stream_rx->ep_addr) {
+    tu_edpt_stream_read_xfer_complete(stream_rx, xferred_bytes);
 
-    // Check for wanted char and invoke callback if needed
-    if (((signed char) p_cdc->wanted_char) != -1) {
+    // Check for wanted char and invoke wanted callback (multiple times if multiple wanted received)
+    if (((signed char)p_cdc->wanted_char) != -1) {
       for (uint32_t i = 0; i < xferred_bytes; i++) {
-        if ((p_cdc->wanted_char == (char) p_epbuf->epout[i]) && !tu_fifo_empty(&p_cdc->rx_ff)) {
+        if ((p_cdc->wanted_char == (char)stream_rx->ep_buf[i]) && !tu_edpt_stream_empty(stream_rx)) {
           tud_cdc_rx_wanted_cb(itf, p_cdc->wanted_char);
         }
       }
     }
 
-    // invoke receive callback (if there is still data)
-    if (!tu_fifo_empty(&p_cdc->rx_ff)) {
+    // invoke receive callback if there is still data
+    if (!tu_edpt_stream_empty(stream_rx)) {
       tud_cdc_rx_cb(itf);
     }
 
-    // prepare for OUT transaction
-    _prep_out_transaction(itf);
+    tu_edpt_stream_read_xfer(rhport, stream_rx); // prepare for more data
   }
 
   // Data sent to host, we continue to fetch from tx fifo to send.
   // Note: This will cause incorrect baudrate set in line coding.
   //       Though maybe the baudrate is not really important !!!
-  if (ep_addr == p_cdc->ep_in) {
+  if (ep_addr == stream_tx->ep_addr) {
     // invoke transmit callback to possibly refill tx fifo
     tud_cdc_tx_complete_cb(itf);
 
-    if (0 == tud_cdc_n_write_flush(itf)) {
-      // If there is no data left, a ZLP should be sent if
-      // xferred_bytes is multiple of EP Packet size and not zero
-      if (0 == tu_fifo_count(&p_cdc->tx_ff) && xferred_bytes > 0 && (0 == (xferred_bytes & (BULK_PACKET_SIZE - 1)))) {
-        if (usbd_edpt_claim(rhport, p_cdc->ep_in)) {
-          TU_ASSERT(usbd_edpt_xfer(rhport, p_cdc->ep_in, NULL, 0, false));
-        }
-      }
+    if (0 == tu_edpt_stream_write_xfer(rhport, stream_tx)) {
+      // If there is no data left, a ZLP should be sent if needed
+      tu_edpt_stream_write_zlp_if_needed(rhport, stream_tx, xferred_bytes);
     }
   }
 
diff --git a/src/class/cdc/cdc_host.c b/src/class/cdc/cdc_host.c
index 7fdf0a7b9..35717ddf6 100644
--- a/src/class/cdc/cdc_host.c
+++ b/src/class/cdc/cdc_host.c
@@ -298,6 +298,7 @@ TU_VERIFY_STATIC(TU_ARRAY_SIZE(serial_drivers) == SERIAL_DRIVER_COUNT, "Serial d
 //--------------------------------------------------------------------+
 // 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 +365,7 @@ static cdch_interface_t* get_itf_by_xfer(const tuh_xfer_t * xfer) {
         #endif
 
         default:
-          break;
+          break; // unknown driver
       }
     }
   }
@@ -389,8 +390,6 @@ 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
 //--------------------------------------------------------------------+
@@ -519,7 +518,7 @@ bool tuh_cdc_read_clear (uint8_t 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);
+  (void)tu_edpt_stream_read_xfer(p_cdc->daddr, &p_cdc->stream.rx);
   return ret;
 }
 
@@ -648,13 +647,10 @@ 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, CFG_TUH_CDC_TX_EPSIZE));
+    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, CFG_TUH_CDC_RX_EPSIZE));
   }
 
   return true;
@@ -663,8 +659,8 @@ 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 +670,9 @@ 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 +690,12 @@ 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 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(daddr, &p_cdc->stream.tx, xferred_bytes);
     }
   } else if (ep_addr == p_cdc->stream.rx.ep_addr) {
     #if CFG_TUH_CDC_FTDI
@@ -718,7 +711,6 @@ 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
     }
 
@@ -727,7 +719,7 @@ bool cdch_xfer_cb(uint8_t daddr, uint8_t ep_addr, xfer_result_t event, uint32_t
   } else if (ep_addr == p_cdc->ep_notif) {
     // TODO handle notification endpoint
   } else {
-    TU_ASSERT(false);
+    return false;
   }
 
   return true;
@@ -736,20 +728,17 @@ 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(tuh_edpt_open(p_cdc->daddr, desc_ep));
+    tu_edpt_stream_t *stream =
+      (tu_edpt_dir(desc_ep->bEndpointAddress) == TUSB_DIR_IN) ? &p_cdc->stream.rx : &p_cdc->stream.tx;
+    tu_edpt_stream_open(stream, 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;
@@ -832,6 +821,7 @@ 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,