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ALSA: snd-usb: fix cross-interface streaming devices 

Commit 68e67f40b ("ALSA: snd-usb: move calls to usb_set_interface")
saved us some unnecessary calls to snd_usb_set_interface() but ignored
the fact that there is at least one device out there which operates on
two endpoint in different interfaces simultaniously.

Take care for this by catching the case where data and sync endpoints
are located on different interfaces and calling snd_usb_set_interface()
between the start of the two endpoints.

Signed-off-by: Daniel Mack <zonque@gmail.com>
Reported-by: Robert M. Albrecht <linux@romal.de>
Cc: stable@kernel.org [v3.5+]
Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Daniel Mack 2012-08-30 18:52:31 +02:00 committed by Takashi Iwai
parent 245baf983c
commit 2e4a263ca8
1 changed files with 15 additions and 0 deletions
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15
sound/usb/pcm.c
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@ -236,6 +236,21 @@ static int start_endpoints(struct snd_usb_substream *subs, int can_sleep)
!test_and_set_bit(SUBSTREAM_FLAG_SYNC_EP_STARTED, &subs->flags)) {
struct snd_usb_endpoint *ep = subs->sync_endpoint;
if (subs->data_endpoint->iface != subs->sync_endpoint->iface ||
subs->data_endpoint->alt_idx != subs->sync_endpoint->alt_idx) {
err = usb_set_interface(subs->dev,
subs->sync_endpoint->iface,
subs->sync_endpoint->alt_idx);
if (err < 0) {
snd_printk(KERN_ERR
"%d:%d:%d: cannot set interface (%d)\n",
subs->dev->devnum,
subs->sync_endpoint->iface,
subs->sync_endpoint->alt_idx, err);
return -EIO;
}
}
snd_printdd(KERN_DEBUG "Starting sync EP @%p\n", ep);
ep->sync_slave = subs->data_endpoint;