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.
Signed-off-by: Takashi Iwai tiwai@suse.de --- sound/usb/card.h | 3 ++- sound/usb/endpoint.c | 4 ++++ sound/usb/pcm.c | 29 ++++++++++++++++++++--------- 3 files changed, 26 insertions(+), 10 deletions(-)
diff --git a/sound/usb/card.h b/sound/usb/card.h index 746a765b2437..a00caa1db37e 100644 --- a/sound/usb/card.h +++ b/sound/usb/card.h @@ -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; };
diff --git a/sound/usb/endpoint.c b/sound/usb/endpoint.c index 06241568abf7..8e164d71d9ac 100644 --- a/sound/usb/endpoint.c +++ b/sound/usb/endpoint.c @@ -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); }
diff --git a/sound/usb/pcm.c b/sound/usb/pcm.c index 19392117de9e..4dd7f1c9e2af 100644 --- a/sound/usb/pcm.c +++ b/sound/usb/pcm.c @@ -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) {