ALSA: usb-audio: Fix case when USB MIDI interface has more than one extra endpoint descriptor (5c6cd702) · Commits · 戴 / test

The Miditech MIDIFACE 16x16 (USB ID 1290:1749) has more than one extra endpoint descriptor. The first extra descriptor is: 0x06 0x30 0x00 0x00 0x00 0x00 As the code in snd_usbmidi_get_ms_info() looks only at the first extra descriptor to find USB_DT_CS_ENDPOINT the device as such is recognized but there is neither input nor output configured. The patch iterates through the extra descriptors to find the proper one. With this patch the device is correctly configured. Signed-off-by:

Andreas Steinmetz <ast@domdv.de> Link: https://lore.kernel.org/r/1c3b431a86f69e1d60745b6110cdb93c299f120b.camel@domdv.de Signed-off-by:

Takashi Iwai <tiwai@suse.de>

sound/usb/midi.c

+24 −5

Original line number	Diff line number	Diff line
		@@ -1826,6 +1826,28 @@ static int snd_usbmidi_create_endpoints(struct snd_usb_midi *umidi,
		return 0;
		}

		static struct usb_ms_endpoint_descriptor *find_usb_ms_endpoint_descriptor(
		struct usb_host_endpoint *hostep)
		{
		unsigned char *extra = hostep->extra;
		int extralen = hostep->extralen;

		while (extralen > 3) {
		struct usb_ms_endpoint_descriptor *ms_ep =
		(struct usb_ms_endpoint_descriptor *)extra;

		if (ms_ep->bLength > 3 &&
		ms_ep->bDescriptorType == USB_DT_CS_ENDPOINT &&
		ms_ep->bDescriptorSubtype == UAC_MS_GENERAL)
		return ms_ep;
		if (!extra[0])
		break;
		extralen -= extra[0];
		extra += extra[0];
		}
		return NULL;
		}

		/*
		* Returns MIDIStreaming device capabilities.
		*/
		@@ -1863,11 +1885,8 @@ static int snd_usbmidi_get_ms_info(struct snd_usb_midi *umidi,
		ep = get_ep_desc(hostep);
		if (!usb_endpoint_xfer_bulk(ep) && !usb_endpoint_xfer_int(ep))
		continue;
		ms_ep = (struct usb_ms_endpoint_descriptor *)hostep->extra;
		if (hostep->extralen < 4 \|\|
		ms_ep->bLength < 4 \|\|
		ms_ep->bDescriptorType != USB_DT_CS_ENDPOINT \|\|
		ms_ep->bDescriptorSubtype != UAC_MS_GENERAL)
		ms_ep = find_usb_ms_endpoint_descriptor(hostep);
		if (!ms_ep)
		continue;
		if (usb_endpoint_dir_out(ep)) {
		if (endpoints[epidx].out_ep) {

Admin message