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 */