Re: [PATCH] OSS Layer: restart stream after xrun once stream is drained.

[Carlo Wood <carlo@alinoe.com>]

On Sun, Jul 13, 2003 at 04:38:47AM +0200, Carlo Wood wrote:
> I wrote a patch for sound/core/oss/pcm_oss.c, that fixes the ViaVoice
> problem.

Later I wrote a test case that still doesn't get fixed:

>a.out
    Size of a fragment in bytes: 1024
    Allocated fragments for buffering: 2
    Successfully caused an xrun.
    non-blocking fragments: 2
    non-blocking bytes: 2048
    Stream is not restarted after xrun.

now this is expected without my patch, but with
the patch the stream *is* set back to a RUNNING state
again successfully - nevertheless, snd_pcm_update_hw_ptr_interrupt
is not called anymore.

Is there anyone who can get the following test code to work
(by patching the ALSA kernel module, not by changing the test code! ;).

Test code:


#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <unistd.h>
#include <sys/soundcard.h>
#include <time.h>

int main(void)
{
  int fd = open("/dev/dsp", O_RDONLY);
  if (fd == -1) { perror("open"); exit(127); }
  int res = AFMT_S16_LE;
  if (ioctl(fd, SNDCTL_DSP_SETFMT, &res) == -1) {
    perror("ioctl"); exit(127); }
  res = 0;
  if (ioctl(fd, SNDCTL_DSP_STEREO, &res) == -1) {
    perror("ioctl"); exit(127); }
  res = 22050;
  if (ioctl(fd, SOUND_PCM_READ_RATE, 0xbfffdcfc) == -1) {
    perror("ioctl"); exit(127); }
  res = 0x7fff000a;
  if (ioctl(fd, SNDCTL_DSP_SETFRAGMENT, &res) == -1) {
    perror("ioctl"); exit(127); }
  audio_buf_info info;
  if (ioctl(fd, SNDCTL_DSP_GETISPACE, &info) == -1) {
    perror("read"); exit(127); }
  printf("    Size of a fragment in bytes: %d\n", info.fragsize);
  printf("    Allocated fragments for buffering: %d\n", info.fragstotal);
  char buf[1024];
  if (read(fd, buf, sizeof(buf)) < 0) { perror("read"); exit(127); }
  static struct timespec naptime = { 0, 100000000 };
  int count = 0;
  do {
    if (ioctl(fd, SNDCTL_DSP_GETISPACE, &info) == -1) {
      perror("read"); exit(127); }
    nanosleep(&naptime, 0);
    if (++count == 20) { printf("Failed to cause an xrun.\n"); exit(127); }
  } while(info.bytes < info.fragsize * info.fragstotal);
  printf("    Successfully caused an xrun.\n");
  printf("    non-blocking fragments: %d\n", info.fragments);
  printf("    non-blocking bytes: %d\n", info.bytes);
  ssize_t bufsize = info.bytes;
  ssize_t trlen = 0;
  int nf = 0;
  for (;;)
  {
    if (ioctl(fd, SNDCTL_DSP_GETISPACE, &info) == -1) {
      perror("ioctl"); exit(127); }
    if (info.fragments > 0) {
      ssize_t rlen;
      if ((rlen = read(fd, buf, sizeof(buf))) < 0)
      { perror("read"); exit(127); }
      trlen += rlen;
      if (trlen > bufsize) {
        printf("    Read %d bytes: stream successfully restarted.\n", trlen);
	exit(0);
      }
      nf = 0;
    }
    else if (++nf > 10) {
      printf("    Stream is not restarted after xrun.\n");
      exit(1);
    }
  }
  close(fd);
  return 0;
}


Here is some debug output that I generated with added printk's:

Jul 13 17:22:27 ansset kernel: Entering snd_pcm_update_hw_ptr_interrupt
Jul 13 17:22:27 ansset kernel: snd_pcm_update_hw_ptr_interrupt: status->hw_ptr set to 1536
Jul 13 17:22:27 ansset kernel: snd_pcm_capture_avail: boundary = 1073741824, status->hw_ptr = 1536, control->appl_ptr = 512
Jul 13 17:22:27 ansset kernel: Calling snd_pcm_stop, runtime->status->state = SNDRV_PCM_STATE_RUNNING
Jul 13 17:22:27 ansset kernel: Returned from snd_pcm_stop, runtime->status->state = SNDRV_PCM_STATE_XRUN
Jul 13 17:22:27 ansset kernel: Leaving snd_pcm_update_hw_ptr_interrupt with EPIPE
...
Jul 13 17:22:27 ansset kernel: snd_pcm_oss_read3: calling snd_pcm_kernel_ioctl SNDRV_PCM_IOCTL_DRAIN
Jul 13 17:22:27 ansset kernel: snd_pcm_capture_drain: state is SNDRV_PCM_STATE_XRUN.  Calling snd_pcm_change_state.
Jul 13 17:22:27 ansset kernel: snd_pcm_capture_avail: boundary = 1073741824, status->hw_ptr = 1536, control->appl_ptr = 512
Jul 13 17:22:27 ansset kernel: snd_pcm_capture_drain: Returning from snd_pcm_change_state, state is now 5
Jul 13 17:22:27 ansset kernel: Entering snd_pcm_lib_read1
Jul 13 17:22:27 ansset kernel: state is SNDRV_PCM_STATE_DRAINING
Jul 13 17:22:27 ansset kernel: size = 512
Jul 13 17:22:27 ansset kernel: snd_pcm_capture_avail: boundary = 1073741824, status->hw_ptr = 1536, control->appl_ptr = 512
Jul 13 17:22:27 ansset kernel: Leaving snd_pcm_lib_read1; xfer = 512, err = 0
...
Jul 13 17:22:27 ansset kernel: Entering snd_pcm_lib_read1
Jul 13 17:22:27 ansset kernel: state is SNDRV_PCM_STATE_DRAINING
Jul 13 17:22:27 ansset kernel: size = 512
Jul 13 17:22:27 ansset kernel: snd_pcm_capture_avail: boundary = 1073741824, status->hw_ptr = 1536, control->appl_ptr = 1024
Jul 13 17:22:27 ansset kernel: Leaving snd_pcm_lib_read1; xfer = 512, err = 0
Jul 13 17:22:27 ansset kernel: snd_pcm_status: status->hw_ptr copied to be 1536
Jul 13 17:22:27 ansset kernel: Calling snd_pcm_capture_avail()
Jul 13 17:22:27 ansset kernel: snd_pcm_capture_avail: boundary = 1073741824, status->hw_ptr = 1536, control->appl_ptr = 1536
Jul 13 17:22:27 ansset kernel: snd_pcm_capture_avail returned status->avail = 0
Jul 13 17:22:27 ansset kernel: snd_pcm_status_user: status.avail = 0

[start of effect of my patch]

Jul 13 17:22:27 ansset kernel: snd_pcm_oss_read3: calling snd_pcm_kernel_ioctl(SNDRV_PCM_IOCTL_PREPARE)
Jul 13 17:22:27 ansset kernel: snd_pcm_lib_ioctl_reset: status->hw_ptr set to 0
Jul 13 17:22:27 ansset kernel: snd_pcm_oss_read3: state now SNDRV_PCM_STATE_RUNNING
Jul 13 17:22:27 ansset kernel: snd_pcm_update_hw_ptr: status->hw_ptr set to 0
Jul 13 17:22:27 ansset kernel: snd_pcm_capture_avail: boundary = 1073741824, status->hw_ptr = 0, control->appl_ptr = 0
Jul 13 17:22:27 ansset kernel: snd_pcm_status: status->hw_ptr copied to be 0
Jul 13 17:22:27 ansset kernel: snd_pcm_capture_avail: boundary = 1073741824, status->hw_ptr = 0, control->appl_ptr = 0
Jul 13 17:22:27 ansset kernel: snd_pcm_capture_avail returned status->avail = 0
Jul 13 17:22:27 ansset kernel: snd_pcm_status_user: status.avail = 0
Jul 13 17:22:27 ansset kernel: space: bytes = 0, periods = 0, fragstotal = 2, fragsize = 1024

[end of patch effects]

...

but snd_pcm_update_hw_ptr_interrupt is never called anymore,
it only repeats

Jul 13 17:22:27 ansset kernel: snd_pcm_update_hw_ptr: status->hw_ptr set to 0
Jul 13 17:22:27 ansset kernel: snd_pcm_capture_avail: boundary = 1073741824, status->hw_ptr = 0, control->appl_ptr = 0
Jul 13 17:22:27 ansset kernel: snd_pcm_status: status->hw_ptr copied to be 0
Jul 13 17:22:27 ansset kernel: Calling snd_pcm_capture_avail()
Jul 13 17:22:27 ansset kernel: snd_pcm_capture_avail: boundary = 1073741824, status->hw_ptr = 0, control->appl_ptr = 0
Jul 13 17:22:27 ansset kernel: snd_pcm_capture_avail returned status->avail = 0
Jul 13 17:22:27 ansset kernel: snd_pcm_status_user: status.avail = 0
Jul 13 17:22:27 ansset kernel: space: bytes = 0, periods = 0, fragstotal = 2, fragsize = 1024

after that.

-- 
Carlo Wood <carlo@alinoe.com>


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