Re: [alsa-devel] [PATCH]fix mmap emulation bug of recording doesn't work

At Wed, 4 Jul 2007 22:18:24 +0800, Roy Huang wrote:

Record doesn't work if enabling mmap emulation and rate conversion needed, this patch fix this bug.

Thanks for the patch. I need to check your changes in detail as it's not so obvious. What is the problem with rate plugin and mmap-emulation? From what I find in your patch, it's something to do with the hw_ptr update mismatch.

Takashi

diff -uNr alsa-lib-1.0.14a/src/pcm/pcm_hw.c alsa-lib-new/src/pcm/pcm_hw.c --- alsa-lib-1.0.14a/src/pcm/pcm_hw.c 2007-06-11 16:53:13.000000000 +0800 +++ alsa-lib-new/src/pcm/pcm_hw.c 2007-07-04 12:16:31.000000000 +0800 @@ -96,6 +96,7 @@ int shadow_appl_ptr: 1, avail_update_flag: 1, mmap_shm: 1;

•   snd_pcm_uframes_t hw_ptr;
    snd_pcm_uframes_t appl_ptr;
    /* restricted parameters */
    snd_pcm_format_t format;
  

@@ -373,7 +374,9 @@ if (pcm->stream == SND_PCM_STREAM_CAPTURE) { if (hw->mmap_shm) { hw->shadow_appl_ptr = 1;

•                   hw->hw_ptr = 0;
                    hw->appl_ptr = 0;
  

•                   snd_pcm_set_hw_ptr(pcm, &hw->hw_ptr, -1, 0);
                    snd_pcm_set_appl_ptr(pcm, &hw->appl_ptr, -1, 0);
            } else {
                    hw->shadow_appl_ptr = 0;
  

@@ -949,28 +952,91 @@ return size; }

+static inline snd_pcm_uframes_t snd_pcm_hw_capture_avail(snd_pcm_t *pcm) +{

•   snd_pcm_sframes_t avail;
  

•   snd_pcm_hw_t *hw = pcm->private_data;
  

•   avail = hw->mmap_status->hw_ptr - hw->mmap_control->appl_ptr;
  

•   if (avail < 0)
  

•           avail += pcm->boundary;
  

•   return avail;
  

+}

+static snd_pcm_sframes_t snd_pcm_hw_read_mmap(snd_pcm_t *pcm, snd_pcm_uframes_t size) +{

•   snd_pcm_uframes_t xfer = 0;
  

•   snd_pcm_sframes_t err = 0;
  

•   snd_pcm_hw_t *hw = pcm->private_data;
  

•   if (! size)
  

•           return 0;
  

•   while (xfer < size) {
  

•           snd_pcm_uframes_t frames = size - xfer;
  

•           snd_pcm_uframes_t appl_offset = hw->mmap_control->appl_ptr %
  

pcm->buffer_size;

•           snd_pcm_uframes_t cont = pcm->buffer_size - appl_offset;
  

•           if (cont < frames)
  

•                   frames = cont;
  

•           switch (pcm->access) {
  

•           case SND_PCM_ACCESS_MMAP_INTERLEAVED:
  

•           {
  

•                   const snd_pcm_channel_area_t *a =
  

snd_pcm_mmap_areas(pcm);

•                   char *buf = snd_pcm_channel_area_addr(a, appl_offset);
  

•                   err = _snd_pcm_readi(pcm, buf, frames);
  

•                   if (err >= 0)
  

•                           frames = err;
  

•                   break;
  

•           }
  

•           case SND_PCM_ACCESS_MMAP_NONINTERLEAVED:
  

•           {
  

•                   snd_pcm_uframes_t channels = pcm->channels;
  

•                   unsigned int c;
  

•                   void *bufs[channels];
  

•                   const snd_pcm_channel_area_t *areas =
  

snd_pcm_mmap_areas(pcm);

•                   for (c = 0; c < channels; ++c) {
  

•                           const snd_pcm_channel_area_t *a = &areas[c];
  

•                           bufs[c] = snd_pcm_channel_area_addr(a,
  

appl_offset);

•                   }
  

•                   err = _snd_pcm_readn(pcm->fast_op_arg, bufs, frames);
  

•                   if (err >= 0)
  

•                           frames = err;
  

•           }
  

•           default:
  

•                   SNDMSG("invalid access type %d", pcm->access);
  

•                   return -EINVAL;
  

•           }
  

•           if (err < 0)
  

•                   break;
  

•           xfer += frames;
  

•   }
  

•   if (xfer > 0)
  

•           return xfer;
  

•   return err;
  

+}

static snd_pcm_sframes_t snd_pcm_hw_avail_update(snd_pcm_t *pcm) { snd_pcm_hw_t *hw = pcm->private_data;

•   snd_pcm_uframes_t avail;
  

•   snd_pcm_uframes_t avail, xfer_avail;
  
    sync_ptr(hw, 0);
    if (pcm->stream == SND_PCM_STREAM_PLAYBACK) {
            avail = snd_pcm_mmap_playback_avail(pcm);
    } else {
            avail = snd_pcm_mmap_capture_avail(pcm);
  

•           if (avail > 0 && hw->mmap_shm) {
  

•           if (avail < pcm->avail_min && hw->mmap_shm) {
                    snd_pcm_sframes_t err;
  

•                   snd_pcm_hw_t *hw = pcm->private_data;
  

•                   hw->avail_update_flag = 1;
  

•                   err = snd_pcm_read_mmap(pcm, avail);
  

•                   hw->avail_update_flag = 0;
  

•                   if (err < 0)
  

•                           return err;
  

•                   if ((snd_pcm_uframes_t)err != avail)
  

•                           SNDMSG("short read %ld for avail %ld",
  

err, avail);

•                   return err;
  

•           }
  

•                   xfer_avail = snd_pcm_hw_capture_avail(pcm);
  

•                   xfer_avail -= xfer_avail % pcm->xfer_align;
  

•                   if (xfer_avail > 0) {
  

•                           hw->avail_update_flag = 1;
  

•                           err = snd_pcm_hw_read_mmap(pcm, xfer_avail);
  

•                           hw->avail_update_flag = 0;
  

•                           if (err < 0)
  

•                                   return err;
  

•                           hw->hw_ptr += err;
  

•                           avail = snd_pcm_mmap_capture_avail(pcm);
  

•                   }
  

•           }
    }
    switch (FAST_PCM_STATE(hw)) {
    case SNDRV_PCM_STATE_RUNNING:
  

---

Alsa-devel mailing list Alsa-devel@alsa-project.org http://mailman.alsa-project.org/mailman/listinfo/alsa-devel