Re: [PATCH v3 kernel 2/3] Extend snd_pcm_ops and snd_pcm_runtime

[Tim Cussins <timcussins@eml.cc>]

Hi,

On 06/02/15 16:38, Pierre-Louis Bossart wrote:
> On 02/06/2015 10:16 AM, Tim Cussins wrote:
>> snd_pcm_ops picks up methods for:
>>
>> - start_at - start_at_abort - start_at_gettime
>>
>> For startat requests involving audio hardware clocks, ALSA core
>> delegates to the driver using these methods, should they exist.
>>
>> snd_pcm_runtime gains fields that contain the current state of the
>> startat timer, if any. This allows cancellation and querying.
>>
>> Signed-off-by: Tim Cussins <timcussins@eml.cc>
>>
>> diff --git a/include/sound/pcm.h b/include/sound/pcm.h index
>> 07299b2..a414fec 100644 --- a/include/sound/pcm.h +++
>> b/include/sound/pcm.h @@ -73,6 +73,9 @@ struct snd_pcm_ops {
>> snd_pcm_uframes_t (*pointer)(struct snd_pcm_substream *substream);
>> int (*wall_clock)(struct snd_pcm_substream *substream, struct
>> timespec *audio_ts); +	int (*start_at)(struct snd_pcm_substream
>> *substream, int startat_clock_type, const struct timespec *ts); +
>> int (*start_at_abort)(struct snd_pcm_substream *substream); +	int
>> (*start_at_gettime)(struct snd_pcm_substream *substream, int
>> startat_clock_type, struct timespec *current_time);
>
> What is the purpose of this _gettime? If the app relies on regular
> system time then it doesn't need to use this and if it relies on the
> link then doesn't this routine duplicate the audio timestamp stuff i
> am still working on.

This patch is written to stand on its own, without timestamping 
evolutions. Once your patch is in, this patch would be rebased on your 
work :)

>> int (*copy)(struct snd_pcm_substream *substream, int channel,
>> snd_pcm_uframes_t pos, void __user *buf, snd_pcm_uframes_t count);
>> @@ -368,6 +371,12 @@ struct snd_pcm_ runtime { #ifdef
>> CONFIG_SND_PCM_XRUN_DEBUG struct snd_pcm_hwptr_log *hwptr_log;
>> #endif + +	bool startat_timer_running; +	/* The following values
>> are valid if startat_timer_running == true */ +	int
>> startat_clock_type;			/* startat clock type of current timer */ +
>> struct timespec startat_start_time;	/* start time of current timer
>> */ +	void* startat_timer_data;		/* data associated with current
>> timer */ };
>>
>> struct snd_pcm_group {		/* keep linked substreams */
>>
>