[patch 045/123] ALSA: usb-audio: reduce MIDI packet size to work around broken firmware

[Greg KH]

2.6.33-stable review patch.  If anyone has any objections, please let me know.

-----------------

From: Clemens Ladisch <clemens@xxxxxxxxxx>

commit f167e1d073278fe231bbdd5d6c24fb9d091aa544 upstream.

Extend the list of devices whose firmware does not expect more than one
USB MIDI packet in one USB packet.

bug report: https://bugtrack.alsa-project.org/alsa-bug/view.php?id=3752

Signed-off-by: Clemens Ladisch <clemens@xxxxxxxxxx>
Signed-off-by: Jaroslav Kysela <perex@xxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
 sound/usb/usbmidi.c |   18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

--- a/sound/usb/usbmidi.c
+++ b/sound/usb/usbmidi.c
@@ -1162,10 +1162,22 @@ static int snd_usbmidi_out_endpoint_crea
 		pipe = usb_sndintpipe(umidi->dev, ep_info->out_ep);
 	else
 		pipe = usb_sndbulkpipe(umidi->dev, ep_info->out_ep);
-	if (umidi->usb_id == USB_ID(0x0a92, 0x1020)) /* ESI M4U */
-		ep->max_transfer = 4;
-	else
+	switch (umidi->usb_id) {
+	default:
 		ep->max_transfer = usb_maxpacket(umidi->dev, pipe, 1);
+		break;
+		/*
+		 * Various chips declare a packet size larger than 4 bytes, but
+		 * do not actually work with larger packets:
+		 */
+	case USB_ID(0x0a92, 0x1020): /* ESI M4U */
+	case USB_ID(0x1430, 0x474b): /* RedOctane GH MIDI INTERFACE */
+	case USB_ID(0x15ca, 0x0101): /* Textech USB Midi Cable */
+	case USB_ID(0x15ca, 0x1806): /* Textech USB Midi Cable */
+	case USB_ID(0x1a86, 0x752d): /* QinHeng CH345 "USB2.0-MIDI" */
+		ep->max_transfer = 4;
+		break;
+	}
 	for (i = 0; i < OUTPUT_URBS; ++i) {
 		buffer = usb_buffer_alloc(umidi->dev,
 					  ep->max_transfer, GFP_KERNEL,


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