Add functionality to abort an ongoing transfer

src/class/cdc/cdc_device.c

@@ -353,6 +353,16 @@ bool cdcd_control_request(uint8_t rhport, tusb_control_request_t const * request
       bool const dtr = tu_bit_test(request->wValue, 0);
       bool const rts = tu_bit_test(request->wValue, 1);
 
+#if CFG_TUD_CDC_CLEAR_AT_CONNECTION
+      // DTE connected event (if DTE supports DTR bit)
+      if ( dtr && !tu_bit_test(p_cdc->line_state, 0) )
+      {
+        // Clear not transmitted data
+        usbd_edpt_xfer_abort(rhport, p_cdc->ep_in);
+        tu_fifo_clear(&p_cdc->tx_ff);
+      }
+#endif
+
       p_cdc->line_state = (uint8_t) request->wValue;
 
       // Disable fifo overwriting if DTR bit is set

src/device/dcd.h

@@ -133,6 +133,9 @@ void dcd_edpt_close        (uint8_t rhport, uint8_t ep_addr) TU_ATTR_WEAK;
 // Submit a transfer, When complete dcd_event_xfer_complete() is invoked to notify the stack
 bool dcd_edpt_xfer        (uint8_t rhport, uint8_t ep_addr, uint8_t * buffer, uint16_t total_bytes);
 
+// Abort a ongoing transfer
+TU_ATTR_WEAK bool dcd_edpt_xfer_abort(uint8_t rhport, uint8_t ep_addr);
+
 // Stall endpoint
 void dcd_edpt_stall       (uint8_t rhport, uint8_t ep_addr);
 

src/device/usbd.c

@@ -1100,6 +1100,33 @@ bool usbd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t * buffer, uint16_t
   }
 }
 
+bool usbd_edpt_xfer_abort(uint8_t rhport, uint8_t ep_addr)
+{
+  uint8_t const epnum = tu_edpt_number(ep_addr);
+  uint8_t const dir   = tu_edpt_dir(ep_addr);
+
+  TU_LOG2("  Abort XFER EP %02X ... ", ep_addr);
+
+  // Abort API is optional for DCD
+  if ( dcd_edpt_xfer_abort )
+  {
+    if ( dcd_edpt_xfer_abort(rhport, ep_addr) )
+    {
+      _usbd_dev.ep_status[epnum][dir].busy = false;
+      TU_LOG2("OK\r\n");
+      return true;
+    }else
+    {
+      TU_LOG2("failed\r\n");
+      return false;
+    }
+  }else
+  {
+    TU_LOG2("no DCD support\r\n");
+    return false;
+  }
+}
+
 bool usbd_edpt_busy(uint8_t rhport, uint8_t ep_addr)
 {
   (void) rhport;

src/device/usbd_pvt.h

@@ -70,6 +70,9 @@ void usbd_edpt_close(uint8_t rhport, uint8_t ep_addr);
 // Submit a usb transfer
 bool usbd_edpt_xfer(uint8_t rhport, uint8_t ep_addr, uint8_t * buffer, uint16_t total_bytes);
 
+// Abort a scheduled transfer
+bool usbd_edpt_xfer_abort(uint8_t rhport, uint8_t ep_addr);
+
 // Check if endpoint transferring is complete
 bool usbd_edpt_busy(uint8_t rhport, uint8_t ep_addr);