[ALSA] usb-audio: work around wrong wMaxPacketSize on ESI M4U
Add a workaround for the ESI M4U that claims to support 32-byte packets
but ignores the remaining bytes of packets bigger than four bytes.
Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Jaroslav Kysela <perex@suse.cz>
diff --git a/sound/usb/usbmidi.c b/sound/usb/usbmidi.c
index 911f448..99295f9 100644
--- a/sound/usb/usbmidi.c
+++ b/sound/usb/usbmidi.c
@@ -965,7 +965,11 @@
}
/* we never use interrupt output pipes */
pipe = usb_sndbulkpipe(umidi->chip->dev, ep_info->out_ep);
- ep->max_transfer = usb_maxpacket(umidi->chip->dev, pipe, 1);
+ if (umidi->chip->usb_id == USB_ID(0x0a92, 0x1020)) /* ESI M4U */
+ /* FIXME: we need more URBs to get reasonable bandwidth here: */
+ ep->max_transfer = 4;
+ else
+ ep->max_transfer = usb_maxpacket(umidi->chip->dev, pipe, 1);
buffer = usb_buffer_alloc(umidi->chip->dev, ep->max_transfer,
GFP_KERNEL, &ep->urb->transfer_dma);
if (!buffer) {