USB: Gadget: Initialize wMaxPacketSize if not already set

Currently, for ISO and INT, a protocol driver must chose the value for
wMaxPacketSize arbitrarily. The value may be too low, resulting in lesser
than efficient operation or high enough to not work with all UDC drivers.

Take un-initialized wMaxPacketSize as a hint to provide maximum
possible packetsize for the selected endpoint. The protocol may
then choose a value not bigger than that.
Signed-off-by: Jassi Brar <jassi.brar@samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/gadget/epautoconf.c

@@ -128,6 +128,13 @@ ep_matches (
 		}
 	}
 
+	/*
+	 * If the protocol driver hasn't yet decided on wMaxPacketSize
+	 * and wants to know the maximum possible, provide the info.
+	 */
+	if (desc->wMaxPacketSize == 0)
+		desc->wMaxPacketSize = cpu_to_le16(ep->maxpacket);
+
 	/* endpoint maxpacket size is an input parameter, except for bulk
 	 * where it's an output parameter representing the full speed limit.
 	 * the usb spec fixes high speed bulk maxpacket at 512 bytes.