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alsa: Add back in code to guess the correct ALSA device prefix.

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This commit is contained in:
Ryan C. Gordon
2024-12-15 13:55:25 -05:00
parent b108b54c6a
commit ff96c59df4
1 changed files with 50 additions and 2 deletions
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52
src/audio/alsa/SDL_alsa_audio.c
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@@ -246,6 +246,51 @@ static bool LoadALSALibrary(void)
#endif // SDL_AUDIO_DRIVER_ALSA_DYNAMIC
static const char *ALSA_device_prefix = NULL;
static void ALSA_guess_device_prefix(void)
{
if (ALSA_device_prefix) {
return; // already calculated.
}
// Apparently there are several different ways that ALSA lists
// actual hardware. It could be prefixed with "hw:" or "default:"
// or "sysdefault:" and maybe others. Go through the list and see
// if we can find a preferred prefix for the system.
static const char *const prefixes[] = {
"hw:", "sysdefault:", "default:"
};
void **hints = NULL;
if (ALSA_snd_device_name_hint(-1, "pcm", &hints) == 0) {
for (int i = 0; hints[i]; i++) {
char *name = ALSA_snd_device_name_get_hint(hints[i], "NAME");
if (name) {
for (int j = 0; j < SDL_arraysize(prefixes); j++) {
const char *prefix = prefixes[j];
const size_t prefixlen = SDL_strlen(prefix);
if (SDL_strncmp(name, prefix, prefixlen) == 0) {
ALSA_device_prefix = prefix;
break;
}
}
free(name); // This should NOT be SDL_free()
if (ALSA_device_prefix) {
break;
}
}
}
}
if (!ALSA_device_prefix) {
ALSA_device_prefix = prefixes[0]; // oh well.
}
LOGDEBUG("device prefix is probably '%s'", ALSA_device_prefix);
}
typedef struct ALSA_Device
{
// the unicity key is the couple (id,recording)
@@ -293,7 +338,7 @@ static char *get_pcm_str(void *handle)
if (SDL_strlen(dev->id) == 0) {
pcm_str = SDL_strdup("default");
} else {
SDL_asprintf(&pcm_str, "default:CARD=%s", dev->id);
SDL_asprintf(&pcm_str, "%sCARD=%s", ALSA_device_prefix, dev->id);
}
return pcm_str;
}
@@ -1512,7 +1557,8 @@ static void ALSA_HotplugIteration(bool *has_default_output, bool *has_default_re
}
char ctl_name[64];
SDL_snprintf(ctl_name, sizeof (ctl_name), "hw:%d", card_idx); // card_idx >= 0
SDL_snprintf(ctl_name, sizeof (ctl_name), "%s%d", ALSA_device_prefix, card_idx); // card_idx >= 0
LOGDEBUG("hotplug ctl_name = '%s'", ctl_name);
r = ALSA_snd_ctl_open(&ctl, ctl_name, 0);
if (r < 0) {
@@ -1616,6 +1662,8 @@ static int SDLCALL ALSA_HotplugThread(void *arg)
static void ALSA_DetectDevices(SDL_AudioDevice **default_playback, SDL_AudioDevice **default_recording)
{
ALSA_guess_device_prefix();
// ALSA doesn't have a concept of a changeable default device, afaik, so we expose a generic default
// device here. It's the best we can do at this level.
bool has_default_playback = false, has_default_recording = false;