USB: Slightly refactored EP OUT handler

Now the release() function only performs the action that is called for,
i.e. release the endpoint and let it receive data. All the buffers handling
has been inlined in the callers, this also slightly improves performance
because it allows to remove some redundant checks.

Author: cmaglie

cores/arduino/USB/SAMD21_USBDevice.h

@@ -195,6 +195,10 @@ void USBDevice_SAMD21G18x::calibrate() {
 	usb.PADCAL.bit.TRIM   = pad_trim;
 }
 
+/*
+ * USB EP generic handlers.
+ */
+
 class EPHandler {
 public:
 	virtual void handleEndpoint() = 0;
@@ -218,6 +222,8 @@ class DoubleBufferedEPOutHandler : public EPHandler {
 		usbd.epBank0SetSize(ep, 64);
 		usbd.epBank0SetType(ep, 3); // BULK OUT
 
+		usbd.epBank0SetAddress(ep, data0);
+
 		release();
 	}
 
@@ -229,12 +235,12 @@ class DoubleBufferedEPOutHandler : public EPHandler {
 			}
 			if (first0 == last0) {
 				first0 = 0;
-				last0 = 0;
+				current = 1;
 				ready0 = false;
 				if (notify) {
+					notify = false;
 					release();
 				}
-				current = 1;
 				return -1;
 			}
 			return data0[first0++];
@@ -244,12 +250,12 @@ class DoubleBufferedEPOutHandler : public EPHandler {
 			}
 			if (first1 == last1) {
 				first1 = 0;
-				last1 = 0;
+				current = 0;
 				ready1 = false;
 				if (notify) {
+					notify = false;
 					release();
 				}
-				current = 0;
 				return -1;
 			}
 			return data1[first1++];
@@ -262,16 +268,29 @@ class DoubleBufferedEPOutHandler : public EPHandler {
 		{
 			// Ack Transfer complete
 			usbd.epBank0AckTransferComplete(ep);
+			//usbd.epBank0AckTransferFailed(ep);
 
 			// Update counters and swap banks
 			if (incoming == 0) {
 				last0 = usbd.epBank0ByteCount(ep);
-				ready0 = true;
 				incoming = 1;
+				usbd.epBank0SetAddress(ep, data1);
+				ready0 = true;
+				if (ready1) {
+					notify = true;
+					return;
+				}
+				notify = false;
 			} else {
 				last1 = usbd.epBank0ByteCount(ep);
-				ready1 = true;
 				incoming = 0;
+				usbd.epBank0SetAddress(ep, data0);
+				ready1 = true;
+				if (ready0) {
+					notify = true;
+					return;
+				}
+				notify = false;
 			}
 			release();
 		}
@@ -295,28 +314,11 @@ class DoubleBufferedEPOutHandler : public EPHandler {
 	}
 
 	void release() {
-		if (incoming == 0) {
-			if (ready0) {
-				notify = true;
-				return;
-			}
-			usbd.epBank0SetAddress(ep, data0);
-		} else {
-			if (ready1) {
-				notify = true;
-				return;
-			}
-			usbd.epBank0SetAddress(ep, data1);
-		}
-		usbd.epBank0AckTransferComplete(ep);
-		//usbd.epBank0AckTransferFailed(ep);
-		usbd.epBank0EnableTransferComplete(ep);
-
 		// Release OUT EP
+		usbd.epBank0EnableTransferComplete(ep);
 		usbd.epBank0SetMultiPacketSize(ep, size);
 		usbd.epBank0SetByteCount(ep, 0);
 		usbd.epBank0ResetReady(ep);
-		notify = false;
 	}
 
 private: