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Commit c75a8a7a authored by Daniel Mack's avatar Daniel Mack Committed by Takashi Iwai
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ALSA: snd-usb: add support for implicit feedback 



Implicit feedback is a streaming mode that does not rely on dedicated
sync endpoints but uses the information provided by record streams to
clock output streams. Now that the streaming logic is decoupled from the
PCM streams, this is easy to implement.

Signed-off-by: default avatarDaniel Mack <zonque@gmail.com>
Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
parent d399ff95

sound/usb/pcm.c

+26 −11
Original line number Diff line number Diff line
@@ -301,7 +301,7 @@ static int set_format(struct snd_usb_substream *subs, struct audioformat *fmt) 
	struct usb_interface *iface;

	unsigned int ep, attr;

	int is_playback = subs->direction == SNDRV_PCM_STREAM_PLAYBACK;

	int err;

	int err, implicit_fb = 0;



	iface = usb_ifnum_to_if(dev, fmt->iface);

	if (WARN_ON(!iface))
@@ -326,25 +326,34 @@ static int set_format(struct snd_usb_substream *subs, struct audioformat *fmt) 
	 * assume it as adaptive-out or sync-in.

	 */

	attr = fmt->ep_attr & USB_ENDPOINT_SYNCTYPE;

	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):

		if (is_playback) {

			implicit_fb = 1;

			ep = 0x81;

			iface = usb_ifnum_to_if(dev, 2);



			if (!iface || iface->num_altsetting == 0)

				return -EINVAL;



			alts = &iface->altsetting[1];

			goto add_sync_ep;

		}

	}



	if (((is_playback && attr == USB_ENDPOINT_SYNC_ASYNC) ||

	     (!is_playback && attr == USB_ENDPOINT_SYNC_ADAPTIVE)) &&

	    altsd->bNumEndpoints >= 2) {

		/* check sync-pipe endpoint */

		/* ... and check descriptor size before accessing bSynchAddress

		   because there is a version of the SB Audigy 2 NX firmware lacking

		   the audio fields in the endpoint descriptors */

		if ((get_endpoint(alts, 1)->bmAttributes & USB_ENDPOINT_XFERTYPE_MASK) != 0x01 ||

		    (get_endpoint(alts, 1)->bLength >= USB_DT_ENDPOINT_AUDIO_SIZE &&

		     get_endpoint(alts, 1)->bSynchAddress != 0)) {

		     get_endpoint(alts, 1)->bSynchAddress != 0 &&

		     !implicit_fb)) {

			snd_printk(KERN_ERR "%d:%d:%d : invalid synch pipe\n",

				   dev->devnum, fmt->iface, fmt->altsetting);

			return -EINVAL;
@@ -352,16 +361,22 @@ static int set_format(struct snd_usb_substream *subs, struct audioformat *fmt) 
		ep = get_endpoint(alts, 1)->bEndpointAddress;

		if (get_endpoint(alts, 0)->bLength >= USB_DT_ENDPOINT_AUDIO_SIZE &&

		    (( is_playback && ep != (unsigned int)(get_endpoint(alts, 0)->bSynchAddress | USB_DIR_IN)) ||

		     (!is_playback && ep != (unsigned int)(get_endpoint(alts, 0)->bSynchAddress & ~USB_DIR_IN)))) {

		     (!is_playback && ep != (unsigned int)(get_endpoint(alts, 0)->bSynchAddress & ~USB_DIR_IN)) ||

		     ( is_playback && !implicit_fb))) {

			snd_printk(KERN_ERR "%d:%d:%d : invalid synch pipe\n",

				   dev->devnum, fmt->iface, fmt->altsetting);

			return -EINVAL;

		}



		implicit_fb = (get_endpoint(alts, 1)->bmAttributes & USB_ENDPOINT_USAGE_MASK)

				== USB_ENDPOINT_USAGE_IMPLICIT_FB;



add_sync_ep:

		subs->sync_endpoint = snd_usb_add_endpoint(subs->stream->chip,

							   alts, ep, !subs->direction,

							   implicit_fb ?

								SND_USB_ENDPOINT_TYPE_DATA :

								SND_USB_ENDPOINT_TYPE_SYNC);



		if (!subs->sync_endpoint)

			return -EINVAL;