From ff96c59df4f0b706458ac8fe059c566011cf58e5 Mon Sep 17 00:00:00 2001
From: "Ryan C. Gordon" <[EMAIL REDACTED]>
Date: Sun, 15 Dec 2024 13:55:25 -0500
Subject: [PATCH] alsa: Add back in code to guess the correct ALSA device
prefix.
---
src/audio/alsa/SDL_alsa_audio.c | 52 +++++++++++++++++++++++++++++++--
1 file changed, 50 insertions(+), 2 deletions(-)
diff --git a/src/audio/alsa/SDL_alsa_audio.c b/src/audio/alsa/SDL_alsa_audio.c
index effa180871f77..4a6bfa8b31952 100644
--- a/src/audio/alsa/SDL_alsa_audio.c
+++ b/src/audio/alsa/SDL_alsa_audio.c
@@ -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;