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* [PATCH] ALSA: usb-audio: Assume first control interface is for audio
@ 2010-09-02  9:13 Daniel Mack
  2010-09-02  9:59 ` Takashi Iwai
  2010-09-10 17:15 ` Felix Homann
  0 siblings, 2 replies; 5+ messages in thread
From: Daniel Mack @ 2010-09-02  9:13 UTC (permalink / raw)
  To: alsa-devel; +Cc: tiwai

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>
---
 sound/usb/card.c |    8 +++++++-
 1 files changed, 7 insertions(+), 1 deletions(-)

diff --git a/sound/usb/card.c b/sound/usb/card.c
index 9feb00c..b443a33 100644
--- a/sound/usb/card.c
+++ b/sound/usb/card.c
@@ -465,7 +465,13 @@ static void *snd_usb_audio_probe(struct usb_device *dev,
 			goto __error;
 	}
 
-	chip->ctrl_intf = alts;
+	/*
+	 * 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) {
 		/* create normal USB audio interfaces */
-- 
1.7.0.4

^ permalink raw reply related	[flat|nested] 5+ messages in thread

end of thread, other threads:[~2010-09-10 17:15 UTC | newest]

Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2010-09-02  9:13 [PATCH] ALSA: usb-audio: Assume first control interface is for audio Daniel Mack
2010-09-02  9:59 ` Takashi Iwai
2010-09-10 16:15   ` Daniel Mack
2010-09-10 17:06     ` [stable] " Greg KH
2010-09-10 17:15 ` Felix Homann

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