Where did snd_pcm_parse_control_id() go?

[Saur2000]

It seems snd_pcm_parse_control_id() was made private in 1.2.5 without any prior deprecation. It is still present in pcm_external.h, and our code now fails to link with:

ld: src/plugin_control.o: in function `plugin_control_load_user_control':
src/plugin_control.c:254: undefined reference to `snd_pcm_parse_control_id'

What are we supposed to use instead? And why is the function still in the header file if it is not in the library?

[perexg]

The function is not very universal. Could you link to your source to reconsider the removal?

[Saur2000]

This is in proprietary code, so I cannot link to it. However, I have extracted the relevant function. I have removed most error handling to keep it shorter, and also removed or obfuscated code that should not be relevant for the issue:

static int plugin_control_load_user_control(snd_config_t *control_config, snd_pcm_t *pcm, UserControl *user_control)
{
  int err, card = -1, cchannels = 2;
  char tmp_name[32];
  snd_pcm_info_t *pcm_info = NULL;

  err = snd_ctl_elem_id_malloc(&user_control->id);
  err = snd_ctl_elem_info_malloc(&user_control->info);
  err = snd_ctl_elem_value_malloc(&user_control->value);
  err = snd_pcm_parse_control_id(control_config, user_control->id, &card, &cchannels, NULL);

  if (card < 0) {
    err = snd_pcm_info_malloc(&pcm_info);
    err = snd_pcm_info(pcm, pcm_info);
    card = snd_pcm_info_get_card(pcm_info);
    snd_pcm_info_free(pcm_info);

    if (card < 0) {
      return -EINVAL;
    }
  }

  sprintf(tmp_name, "hw:%d", card);

  err = snd_ctl_open(&user_control->control_handle, tmp_name, SND_CTL_NONBLOCK);

  snd_ctl_elem_value_set_id(user_control->value, user_control->id);
  snd_ctl_elem_info_set_id(user_control->info, user_control->id);

  err = snd_ctl_elem_info(user_control->control_handle, user_control->info);
  if (err < 0) {
    const char *name;

    if (err != -ENOENT) {
      return err;
    }

    name = snd_ctl_elem_info_get_name(user_control->info);

    if (strcmp(name, USER_CONTROL_NAME_ENABLED) == 0) {
      err = some_function(user_control, cchannels, false);
    } else {
      return -EINVAL;
    }

    err = snd_ctl_elem_unlock(user_control->control_handle, user_control->id);
  }

  return 0;
}

Also note that I am not responsible for this code. I am just trying to make it build with a newer version of alsa-lib as part of updating our platform to Poky Honister from the Yocto Project.

[perexg]

I added the code back (will be in 1.2.6) with the deprecated attribute in f0d540f851de3992a5e285dcea0be7cab293527e . Anyway, I suggest to copy the code to the caller. Called functions (from snd_pcm_parse_control_id() are available).