[alsa-devel] [PATCH 6/9] rate: handle negative values from snd_pcm_mmap_playback_hw_avail

[Alexander E. Patrakov]

15.09.2014 14:49, Takashi Iwai пишет:
> At Sun, 14 Sep 2014 00:30:18 +0600,
> Alexander E. Patrakov wrote:
>>
>> Such negative returns are possible during an underrun if xrun detection
>> is disabled.
>>
>> So, don't store the result in an unsigned variable (where it will
>> overflow), and postpone the trigger in such case, too.
>>
>> Signed-off-by: Alexander E. Patrakov <patrakov at gmail.com>
>> ---
>>
>> The patch is only compile-tested and the second hunk may well be wrong.
>>
>> There are also similar issues in pcm_share.c, but, as I don't completely
>> understand the code there and cannot test that plugin at all due to
>> unrelated crashes, there will be no patch from me.
>
> In general, hw_avail must not be negative before starting the stream.
> If it is, then it means most likely the driver problem, so we should
> return error immediately instead.

Thanks for the review. Would -EBADFD be a correct error code, or do you 
want something different? or maybe even an assert?

>
>
> Takashi
>
>>
>>   src/pcm/pcm_rate.c | 4 ++--
>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/src/pcm/pcm_rate.c b/src/pcm/pcm_rate.c
>> index b436a8e..736d558 100644
>> --- a/src/pcm/pcm_rate.c
>> +++ b/src/pcm/pcm_rate.c
>> @@ -1058,7 +1058,7 @@ static snd_pcm_state_t snd_pcm_rate_state(snd_pcm_t *pcm)
>>   static int snd_pcm_rate_start(snd_pcm_t *pcm)
>>   {
>>   	snd_pcm_rate_t *rate = pcm->private_data;
>> -	snd_pcm_uframes_t avail;
>> +	snd_pcm_sframes_t avail;
>>   		
>>   	if (pcm->stream == SND_PCM_STREAM_CAPTURE)
>>   		return snd_pcm_start(rate->gen.slave);
>> @@ -1069,7 +1069,7 @@ static int snd_pcm_rate_start(snd_pcm_t *pcm)
>>   	gettimestamp(&rate->trigger_tstamp, pcm->tstamp_type);
>>
>>   	avail = snd_pcm_mmap_playback_hw_avail(rate->gen.slave);
>> -	if (avail == 0) {
>> +	if (avail <= 0) {
>>   		/* postpone the trigger since we have no data committed yet */
>>   		rate->start_pending = 1;
>>   		return 0;
>> --
>> 2.1.0
>>


-- 
Alexander E. Patrakov