Re: [PATCH 3/3] ALSA: snd-usb: fix cross-interface streaming devices

[Daniel Mack <zonque@gmail.com>]

On 30.08.2012 18:52, Daniel Mack wrote:
> 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+]


> ---
>  sound/usb/pcm.c | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
> 
> diff --git a/sound/usb/pcm.c b/sound/usb/pcm.c
> index e80b668..fd5e982 100644
> --- a/sound/usb/pcm.c
> +++ b/sound/usb/pcm.c
> @@ -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;
>