[ALSA] usb-audio: add workaround for ESI MIDI Mate/RomIO II

Force low speed USB MIDI devices like the ESI MIDI Mate and RomIO II to
use interrupt transfers because the USB core would not be happy about
low speed bulk transfers.

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Jaroslav Kysela <perex@suse.cz>

sound/usb/usbmidi.c

@@ -1351,6 +1351,13 @@ static int snd_usbmidi_get_ms_info(struct snd_usb_midi* umidi,
 			endpoints[epidx].out_ep = ep->bEndpointAddress & USB_ENDPOINT_NUMBER_MASK;
 			if ((ep->bmAttributes & USB_ENDPOINT_XFERTYPE_MASK) == USB_ENDPOINT_XFER_INT)
 				endpoints[epidx].out_interval = ep->bInterval;
+			else if (snd_usb_get_speed(umidi->chip->dev) == USB_SPEED_LOW)
+				/*
+				 * Low speed bulk transfers don't exist, so
+				 * force interrupt transfers for devices like
+				 * ESI MIDI Mate that try to use them anyway.
+				 */
+				endpoints[epidx].out_interval = 1;
 			endpoints[epidx].out_cables = (1 << ms_ep->bNumEmbMIDIJack) - 1;
 			snd_printdd(KERN_INFO "EP %02X: %d jack(s)\n",
 				    ep->bEndpointAddress, ms_ep->bNumEmbMIDIJack);
@@ -1364,6 +1371,8 @@ static int snd_usbmidi_get_ms_info(struct snd_usb_midi* umidi,
 			endpoints[epidx].in_ep = ep->bEndpointAddress & USB_ENDPOINT_NUMBER_MASK;
 			if ((ep->bmAttributes & USB_ENDPOINT_XFERTYPE_MASK) == USB_ENDPOINT_XFER_INT)
 				endpoints[epidx].in_interval = ep->bInterval;
+			else if (snd_usb_get_speed(umidi->chip->dev) == USB_SPEED_LOW)
+				endpoints[epidx].in_interval = 1;
 			endpoints[epidx].in_cables = (1 << ms_ep->bNumEmbMIDIJack) - 1;
 			snd_printdd(KERN_INFO "EP %02X: %d jack(s)\n",
 				    ep->bEndpointAddress, ms_ep->bNumEmbMIDIJack);