Hi ,
Thanx for the patch . Application of this patch resolves kernel pcm
ring buffer flush problem .
Now SNDCTL_DSP_RESET works properly .
On a suggestive note , as this bug is present in main stream kernel also ,
this patch should also be applied as well .
Thanx & Regards
Amit Nagal
On Mon, Nov 29, 2010 at 5:58 PM, Takashi Iwai <tiwai@xxxxxxx> wrote:
> At Mon, 29 Nov 2010 17:40:03 +0900,
> Amit Nagal wrote:
>>
>> Hi ,
>>
>> Thanx for the reply .
>>
>> we tried SNDCTL_DSP_RESET , but it is not flushing the kernel pcm
>> buffer for us .
>
> It should. It abandons the pending data and resets to the initial
> state before starting the stream.
>
> But, it might be a bug in OSS emulation later. It doesn't seem to
> reset the internal buffer. Try the patch below.
>
>> any other method which we can use ?
>
>> also please lets us the function available with alsa - lib which
>> serves the purpose of flushing
>> the kernel pcm buffer .
>
> snd_pcm_drop() corresponds to it.
>
>
> Takashi
>
> ---
> diff --git a/sound/core/oss/pcm_oss.c b/sound/core/oss/pcm_oss.c
> index 5c8c7df..a4411a3 100644
> --- a/sound/core/oss/pcm_oss.c
> +++ b/sound/core/oss/pcm_oss.c
> @@ -1510,16 +1510,19 @@ static ssize_t snd_pcm_oss_read1(struct snd_pcm_substream *substream, char __use
> static int snd_pcm_oss_reset(struct snd_pcm_oss_file *pcm_oss_file)
> {
> struct snd_pcm_substream *substream;
> + struct snd_pcm_runtime *runtime;
> + int i;
>
> - substream = pcm_oss_file->streams[SNDRV_PCM_STREAM_PLAYBACK];
> - if (substream != NULL) {
> - snd_pcm_kernel_ioctl(substream, SNDRV_PCM_IOCTL_DROP, NULL);
> - substream->runtime->oss.prepare = 1;
> - }
> - substream = pcm_oss_file->streams[SNDRV_PCM_STREAM_CAPTURE];
> - if (substream != NULL) {
> + for (i = 0; i < 2; i++) {
> + substream = pcm_oss_file->streams[i];
> + if (!substream)
> + continue;
> + runtime = substream->runtine;
> snd_pcm_kernel_ioctl(substream, SNDRV_PCM_IOCTL_DROP, NULL);
> - substream->runtime->oss.prepare = 1;
> + runtime->oss.prepare = 1;
> + runtime->oss.buffer_used = 0;
> + runtime->oss.prev_hw_ptr_period = 0;
> + runtime->oss.period_ptr = 0;
> }
> return 0;
> }
>
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