Commit 9c9a3b9d authored by Takashi Iwai's avatar Takashi Iwai
Browse files

ALSA: usb-audio: Rename early_playback_start flag with lowlatency_playback 

This is a preparation patch for the upcoming low-latency improvement
changes.

Rename early_playback_start flag with lowlatency_playback as it's more
intuitive.  The new flag is basically a reverse meaning.

Along with the rename, factor out the code to set the flag to a
function.  This makes the complex condition checks simpler.

Also, the same flag is introduced to snd_usb_endpoint, too, that is
carried from the snd_usb_substream flag.  Currently the endpoint flag
isn't still referred, but will be used in later patches.

Link: https://lore.kernel.org/r/20210929080844.11583-4-tiwai@suse.de


Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
parent 86a42ad0

sound/usb/card.h

+2 −1
Original line number Diff line number Diff line
@@ -126,6 +126,7 @@ struct snd_usb_endpoint { 
	int skip_packets;		/* quirks for devices to ignore the first n packets

					   in a stream */

	bool implicit_fb_sync;		/* syncs with implicit feedback */

	bool lowlatency_playback;	/* low-latency playback mode */

	bool need_setup;		/* (re-)need for configure? */



	/* for hw constraints */
@@ -190,7 +191,7 @@ struct snd_usb_substream { 
	} dsd_dop;



	bool trigger_tstamp_pending_update; /* trigger timestamp being updated from initial estimate */

	bool early_playback_start;	/* early start needed for playback? */

	bool lowlatency_playback;	/* low-latency playback mode */

	struct media_ctl *media_ctl;

};

sound/usb/endpoint.c

+4 −0
Original line number Diff line number Diff line
@@ -794,6 +794,10 @@ void snd_usb_endpoint_set_callback(struct snd_usb_endpoint *ep, 
{

	ep->prepare_data_urb = prepare;

	ep->retire_data_urb = retire;

	if (data_subs)

		ep->lowlatency_playback = data_subs->lowlatency_playback;

	else

		ep->lowlatency_playback = false;

	WRITE_ONCE(ep->data_subs, data_subs);

}

sound/usb/pcm.c

+20 −9
Original line number Diff line number Diff line
@@ -581,6 +581,22 @@ static int snd_usb_hw_free(struct snd_pcm_substream *substream) 
	return 0;

}



/* check whether early start is needed for playback stream */

static int lowlatency_playback_available(struct snd_usb_substream *subs)

{

	struct snd_usb_audio *chip = subs->stream->chip;



	if (subs->direction == SNDRV_PCM_STREAM_CAPTURE)

		return false;

	/* disabled via module option? */

	if (!chip->lowlatency)

		return false;

	/* too short periods? */

	if (subs->data_endpoint->nominal_queue_size >= subs->buffer_bytes)

		return false;

	return true;

}



/*

 * prepare callback

 *
@@ -614,13 +630,8 @@ static int snd_usb_pcm_prepare(struct snd_pcm_substream *substream) 
	subs->period_elapsed_pending = 0;

	runtime->delay = 0;



	/* check whether early start is needed for playback stream */

	subs->early_playback_start =

		subs->direction == SNDRV_PCM_STREAM_PLAYBACK &&

		(!chip->lowlatency ||

		 (subs->data_endpoint->nominal_queue_size >= subs->buffer_bytes));



	if (subs->early_playback_start)

	subs->lowlatency_playback = lowlatency_playback_available(subs);

	if (!subs->lowlatency_playback)

		ret = start_endpoints(subs);



 unlock:
@@ -1412,7 +1423,7 @@ static void prepare_playback_urb(struct snd_usb_substream *subs, 
		subs->trigger_tstamp_pending_update = false;

	}



	if (period_elapsed && !subs->running && !subs->early_playback_start) {

	if (period_elapsed && !subs->running && subs->lowlatency_playback) {

		subs->period_elapsed_pending = 1;

		period_elapsed = 0;

	}
@@ -1466,7 +1477,7 @@ static int snd_usb_substream_playback_trigger(struct snd_pcm_substream *substrea 
					      prepare_playback_urb,

					      retire_playback_urb,

					      subs);

		if (!subs->early_playback_start &&

		if (subs->lowlatency_playback &&

		    cmd == SNDRV_PCM_TRIGGER_START) {

			err = start_endpoints(subs);

			if (err < 0) {