Commit 7b6717e1 authored Sep 02, 2010 by Daniel Mack Committed by Takashi Iwai Sep 02, 2010

ALSA: usb-audio: Assume first control interface is for audio

For devices with more than one control interface, let's assume the first
one contains the audio controls. Unfortunately, there is no field in any
of the descriptors to tell us whether a control interface is for audio
or MIDI controls, so a better check is not easy to implement.

On a composite device with audio and MIDI functions, for example, the
code currently overwrites chip->ctrl_intf, causing operations on the
control interface to fail if they are issued after the device probe.

Signed-off-by: Daniel Mack <daniel@caiaq.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

parent 2bfc96a1

sound/usb/card.c

+7 −1

Original line number	Diff line number	Diff line
		@@ -465,6 +465,12 @@ static void snd_usb_audio_probe(struct usb_device dev,
		goto __error;
		}

		/*
		* For devices with more than one control interface, we assume the
		* first contains the audio controls. We might need a more specific
		* check here in the future.
		*/
		if (!chip->ctrl_intf)
		chip->ctrl_intf = alts;

		if (err > 0) {

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