usb: gadget: f_accessory: Enabled Zero Length Packet (ZLP) for acc_write

DextersHub · toddpoynor · commit bf810cfb96a5 · 2014-08-13T18:45:17.000-07:00
Accessory connected to Android Device requires
Zero Length Packet (ZLP) to be written when data
transferred out from the Android device are multiples
of wMaxPacketSize (64bytes (Full-Speed) / 512bytes (High-Speed))
to end the transfer.

Change-Id: Ib2c2c0ab98ef9afa10e74a720142deca5c0ed476
Signed-off-by: Anson Jacob &lt;ansonkuzhumbil@gmail.com&gt;
diff --git a/drivers/usb/gadget/f_accessory.c b/drivers/usb/gadget/f_accessory.c
@@ -638,10 +638,17 @@ static ssize_t acc_write(struct file *fp, const char __user *buf,
 			break;
 		}
 
-		if (count > BULK_BUFFER_SIZE)
+		if (count > BULK_BUFFER_SIZE) {
 			xfer = BULK_BUFFER_SIZE;
-		else
+			/* ZLP, They will be more TX requests so not yet. */
+			req->zero = 0;
+		} else {
 			xfer = count;
+			/* If the data length is a multple of the
+			 * maxpacket size then send a zero length packet(ZLP).
+			*/
+			req->zero = ((xfer % dev->ep_in->maxpacket) == 0);
+		}
 		if (copy_from_user(req->buf, buf, xfer)) {
 			r = -EFAULT;
 			break;
