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; }

At Tue, 30 Nov 2010 11:51:33 +0900, Amit Nagal wrote:

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 .

Thanks for testing. Yes, I applied the patch now, and it'll be included in the stable kernel as well.

Takashi

Thanx & Regards Amit Nagal

On Mon, Nov 29, 2010 at 5:58 PM, Takashi Iwai tiwai@suse.de 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;  }