RE: [PATCH] ALSA: compress: allow pause and resume during draining

["Gyeongtaek Lee" <gt82.lee@samsung.com>]

On 9/29/20 04:13 PM, Takashi Iwai wrote:
>On Tue, 29 Sep 2020 03:51:35 +0200,
>Gyeongtaek Lee wrote:
>> 
>> On 9/28/20 11:35 PM, Pierre-Louis Bossart wrote:
>> >On 9/28/20 6:13 AM, Jaroslav Kysela wrote:
>> >> Dne 28. 09. 20 v 12:50 Gyeongtaek Lee napsal(a):
>> >>> With a stream with low bitrate, user can't pause or resume the stream
>> >>> near the end of the stream because current ALSA doesn't allow it.
>> >>> If the stream has very low bitrate enough to store whole stream into
>> >>> the buffer, user can't do anything except stop the stream and then
>> >>> restart it from the first.
>> >>> If pause and resume is allowed during draining, user experience can be
>> >>> enhanced.
>> >> 
>> >> It seems that we need a new state to handle the pause + drain condition for
>> >> this case.
>> >> 
>> >> With this proposed change, the pause state in drain is invisible.
>> >
>> >Indeed it's be much nicer to have a new state, e..g 
>> >SNDRV_PCM_STATE_DRAINING_PAUSED.
>> Ok. I will add the new state.
>> >
>> >One concern is that states are defined in uapi/sound/asoc.h, so wouldn't 
>> >this have impacts on userspace as well? We'd change the value of 
>> >SNDRV_PCM_STATE_LAST.
>> >
>> I also agree that adding new state and increase LAST value in the header of uapi
>> could be dangerous. So, I added it to comress_offload.h for now.
>> It could be merged into snd_pcm_state_t in someday with big changes.
>> Could you review the fixed patch below?
>
>Hrm, this resulted in rather more complex changes than the original
>patch.  It shows that introducing yet another state is no good idea
>for this particular case.
>
>Since the possible application's behavior after this pause is as same
>as the normal pause (i.e. either resuming pause or dropping), I find
>it OK to take the original approach.
Thank you for the review.
I think that I should resend the original patch.
Am I right?
>
>
>thanks,
>
>Takashi
>
>> With a stream with low bitrate, user can't pause or resume the stream
>> near the end of the stream because current ALSA doesn't allow it.
>> If the stream has very low bitrate enough to store whole stream into
>> the buffer, user can't do anything except stop the stream and then
>> restart it from first.
>> If pause, resume are allowed during draining, user experience can be
>> enhanced.
>> 
>> New state for pause during draining is defined in compress_offload.h for
>> now. If PCM_STATEs in uapi/sound/asound.h is changed, pcm libraries and
>> userspace application will be affected.
>> 
>> Signed-off-by: Gyeongtaek Lee <gt82.lee@samsung.com>
>> Cc: stable@vger.kernel.org
>> ---
>>  include/uapi/sound/compress_offload.h |  3 ++
>>  sound/core/compress_offload.c         | 47 ++++++++++++++++++++++-----
>>  2 files changed, 41 insertions(+), 9 deletions(-)
>> 
>> diff --git a/include/uapi/sound/compress_offload.h b/include/uapi/sound/compress_offload.h
>> index 7184265c0b0d..f30b9851d1d7 100644
>> --- a/include/uapi/sound/compress_offload.h
>> +++ b/include/uapi/sound/compress_offload.h
>> @@ -189,4 +189,7 @@ struct snd_compr_metadata {
>>  #define SND_COMPR_TRIGGER_DRAIN 7 /*FIXME move this to pcm.h */
>>  #define SND_COMPR_TRIGGER_NEXT_TRACK 8
>>  #define SND_COMPR_TRIGGER_PARTIAL_DRAIN 9
>> +
>> +/* FIXME move this to asound.h */
>> +#define	SNDRV_PCM_STATE_DRAINING_PAUSED	(SNDRV_PCM_STATE_LAST + 1)
>>  #endif
>> diff --git a/sound/core/compress_offload.c b/sound/core/compress_offload.c
>> index 0e53f6f31916..58fbe0d99431 100644
>> --- a/sound/core/compress_offload.c
>> +++ b/sound/core/compress_offload.c
>> @@ -151,6 +151,7 @@ static int snd_compr_free(struct inode *inode, struct file *f)
>>  	case SNDRV_PCM_STATE_RUNNING:
>>  	case SNDRV_PCM_STATE_DRAINING:
>>  	case SNDRV_PCM_STATE_PAUSED:
>> +	case SNDRV_PCM_STATE_DRAINING_PAUSED:
>>  		data->stream.ops->trigger(&data->stream, SNDRV_PCM_TRIGGER_STOP);
>>  		break;
>>  	default:
>> @@ -431,6 +432,7 @@ static __poll_t snd_compr_poll(struct file *f, poll_table *wait)
>>  	case SNDRV_PCM_STATE_RUNNING:
>>  	case SNDRV_PCM_STATE_PREPARED:
>>  	case SNDRV_PCM_STATE_PAUSED:
>> +	case SNDRV_PCM_STATE_DRAINING_PAUSED:
>>  		if (avail >= stream->runtime->fragment_size)
>>  			retval = snd_compr_get_poll(stream);
>>  		break;
>> @@ -708,11 +710,23 @@ static int snd_compr_pause(struct snd_compr_stream *stream)
>>  {
>>  	int retval;
>>  
>> -	if (stream->runtime->state != SNDRV_PCM_STATE_RUNNING)
>> +	switch (stream->runtime->state) {
>> +	case SNDRV_PCM_STATE_RUNNING:
>> +		retval = stream->ops->trigger(stream,
>> +			SNDRV_PCM_TRIGGER_PAUSE_PUSH);
>> +		if (!retval)
>> +			stream->runtime->state = SNDRV_PCM_STATE_PAUSED;
>> +		break;
>> +	case SNDRV_PCM_STATE_DRAINING:
>> +		retval = stream->ops->trigger(stream,
>> +			SNDRV_PCM_TRIGGER_PAUSE_PUSH);
>> +		if (!retval)
>> +			stream->runtime->state =
>> +				SNDRV_PCM_STATE_DRAINING_PAUSED;
>> +		break;
>> +	default:
>>  		return -EPERM;
>> -	retval = stream->ops->trigger(stream, SNDRV_PCM_TRIGGER_PAUSE_PUSH);
>> -	if (!retval)
>> -		stream->runtime->state = SNDRV_PCM_STATE_PAUSED;
>> +	}
>>  	return retval;
>>  }
>>  
>> @@ -720,11 +734,22 @@ static int snd_compr_resume(struct snd_compr_stream *stream)
>>  {
>>  	int retval;
>>  
>> -	if (stream->runtime->state != SNDRV_PCM_STATE_PAUSED)
>> +	switch (stream->runtime->state) {
>> +	case SNDRV_PCM_STATE_PAUSED:
>> +		retval = stream->ops->trigger(stream,
>> +			SNDRV_PCM_TRIGGER_PAUSE_RELEASE);
>> +		if (!retval)
>> +			stream->runtime->state = SNDRV_PCM_STATE_RUNNING;
>> +		break;
>> +	case SNDRV_PCM_STATE_DRAINING_PAUSED:
>> +		retval = stream->ops->trigger(stream,
>> +			SNDRV_PCM_TRIGGER_PAUSE_RELEASE);
>> +		if (!retval)
>> +			stream->runtime->state = SNDRV_PCM_STATE_DRAINING;
>> +		break;
>> +	default:
>>  		return -EPERM;
>> -	retval = stream->ops->trigger(stream, SNDRV_PCM_TRIGGER_PAUSE_RELEASE);
>> -	if (!retval)
>> -		stream->runtime->state = SNDRV_PCM_STATE_RUNNING;
>> +	}
>>  	return retval;
>>  }
>>  
>> @@ -835,7 +860,9 @@ static int snd_compress_wait_for_drain(struct snd_compr_stream *stream)
>>  	 */
>>  
>>  	ret = wait_event_interruptible(stream->runtime->sleep,
>> -			(stream->runtime->state != SNDRV_PCM_STATE_DRAINING));
>> +			(stream->runtime->state != SNDRV_PCM_STATE_DRAINING) &&
>> +			(stream->runtime->state !=
>> +				SNDRV_PCM_STATE_DRAINING_PAUSED));
>>  	if (ret == -ERESTARTSYS)
>>  		pr_debug("wait aborted by a signal\n");
>>  	else if (ret)
>> @@ -857,6 +884,7 @@ static int snd_compr_drain(struct snd_compr_stream *stream)
>>  	case SNDRV_PCM_STATE_SETUP:
>>  	case SNDRV_PCM_STATE_PREPARED:
>>  	case SNDRV_PCM_STATE_PAUSED:
>> +	case SNDRV_PCM_STATE_DRAINING_PAUSED:
>>  		return -EPERM;
>>  	case SNDRV_PCM_STATE_XRUN:
>>  		return -EPIPE;
>> @@ -909,6 +937,7 @@ static int snd_compr_partial_drain(struct snd_compr_stream *stream)
>>  	case SNDRV_PCM_STATE_SETUP:
>>  	case SNDRV_PCM_STATE_PREPARED:
>>  	case SNDRV_PCM_STATE_PAUSED:
>> +	case SNDRV_PCM_STATE_DRAINING_PAUSED:
>>  		return -EPERM;
>>  	case SNDRV_PCM_STATE_XRUN:
>>  		return -EPIPE;
>> 
>> base-commit: a1b8638ba1320e6684aa98233c15255eb803fac7
>> -- 
>> 2.21.0
>> 
>> 
>