[alsa-devel] [PATCH 2/5] ALSA: snd-usb: switch over to new endpoint streaming logic

[Takashi Iwai]

At Tue, 01 Nov 2011 21:57:30 +0100,
Clemens Ladisch wrote:
> 
> On 10/31/2011 01:10 PM, Daniel Mack wrote:
> > @@ -276,6 +312,15 @@ static int set_format(struct snd_usb_substream *subs, struct audioformat *fmt)
> >  	if (((is_playback && attr == USB_ENDPOINT_SYNC_ASYNC) ||
> >  	     (! is_playback && attr == USB_ENDPOINT_SYNC_ADAPTIVE)) &&
> >  	    altsd->bNumEndpoints >= 2) {
> > +		switch (subs->stream->chip->usb_id) {
> > +		case USB_ID(0x0763, 0x2080): /* M-Audio FastTrack Ultra */
> > +		case USB_ID(0x0763, 0x2081):
> > +			ep = 0x81;
> > +			iface = usb_ifnum_to_if(dev, 2);
> > +			alts = &iface->altsetting[1];
> 
> Better check that the device actually has these descriptors.
> 
> > +int snd_usb_substream_capture_trigger(struct snd_pcm_substream *substream, int cmd)
> > +{
> > +	case SNDRV_PCM_TRIGGER_START:
> > +		err = start_endpoints(subs);
> 
> The trigger callback should execute very quickly; the initial URB
> submission should be handled in the prepare callback.

Indeed this is a PITA since long time ago...  In general, it's wrong
to do it in prepare callback.  But we had to do just as a workaround.

Clemens, I thought you wanted to implement some framework for such
devices?


thanks,

Takashi