[alsa-devel] [PATCH v4 02/10] ALSA: core: allow for trigger_tstamp snapshot in .trigger

[Takashi Iwai]

At Fri, 30 Jan 2015 17:55:55 -0600,
Pierre-Louis Bossart wrote:
> 
> Don't use generic snapshot of trigger_tstamp if low-level driver or
> hardware can get a more precise value for better audio/system time
> synchronization.
> 
> Also add definitions for delayed updates if actual trigger tstamp
> can be only be provided after a delay due to hardware constraints.
> 
> Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart at linux.intel.com>
> ---
>  include/sound/pcm.h     | 2 ++
>  sound/core/pcm_native.c | 4 +++-
>  2 files changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/include/sound/pcm.h b/include/sound/pcm.h
> index cd09c1b..a8b98c5 100644
> --- a/include/sound/pcm.h
> +++ b/include/sound/pcm.h
> @@ -279,6 +279,8 @@ struct snd_pcm_runtime {
>  	/* -- Status -- */
>  	struct snd_pcm_substream *trigger_master;
>  	struct timespec trigger_tstamp;	/* trigger timestamp */
> +	bool trigger_tstamp_latched;     /* trigger timestamp latched in low-level driver/hardware */
> +	bool trigger_tstamp_pending_update; /* trigger timestamp being updated from initial estimate */

I don't see trigger_tstamp_pending_update is used anywhere.  Some code
dropped?

>  	int overrange;
>  	snd_pcm_uframes_t avail_max;
>  	snd_pcm_uframes_t hw_ptr_base;	/* Position at buffer restart */
> diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c
> index 7bbc34d..4a97029 100644
> --- a/sound/core/pcm_native.c
> +++ b/sound/core/pcm_native.c
> @@ -810,7 +810,8 @@ static void snd_pcm_trigger_tstamp(struct snd_pcm_substream *substream)
>  	if (runtime->trigger_master == NULL)
>  		return;
>  	if (runtime->trigger_master == substream) {
> -		snd_pcm_gettime(runtime, &runtime->trigger_tstamp);
> +		if (runtime->trigger_tstamp_latched == 0)
> +			snd_pcm_gettime(runtime, &runtime->trigger_tstamp);

A form like "!foo" is preferred for a boolean.

>  	} else {
>  		snd_pcm_trigger_tstamp(runtime->trigger_master);
>  		runtime->trigger_tstamp = runtime->trigger_master->runtime->trigger_tstamp;
> @@ -979,6 +980,7 @@ static int snd_pcm_pre_start(struct snd_pcm_substream *substream, int state)
>  	if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK &&
>  	    !snd_pcm_playback_data(substream))
>  		return -EPIPE;
> +	runtime->trigger_tstamp_latched = 0;

Use "false".


thanks,

Takashi