From c04624972ed63950ca9fb47931339a53d4416ee1 Mon Sep 17 00:00:00 2001
From: "Ryan C. Gordon" <[EMAIL REDACTED]>
Date: Tue, 17 Jun 2025 20:40:00 -0400
Subject: [PATCH] alsa: Simplify ALSA_WaitDevice.
- Check for specific availability instead of waiting for "device ready."
- Don't use snd_pcm_wait, just use a simple SDL_Delay (nothing to recover).
- Fixed SDL_max call that should have been SDL_min (now using SDL_clamp).
- ALSA_RecordDevice() now returns 0 if no availability, which kicks us back
to WaitDevice to try again, as an extra safety check.
---
src/audio/alsa/SDL_alsa_audio.c | 35 ++++++++++++++++-----------------
1 file changed, 17 insertions(+), 18 deletions(-)
diff --git a/src/audio/alsa/SDL_alsa_audio.c b/src/audio/alsa/SDL_alsa_audio.c
index badbc43ec867e..026b9bde5569c 100644
--- a/src/audio/alsa/SDL_alsa_audio.c
+++ b/src/audio/alsa/SDL_alsa_audio.c
@@ -348,26 +348,22 @@ static char *get_pcm_str(void *handle)
// This function waits until it is possible to write a full sound buffer
static bool ALSA_WaitDevice(SDL_AudioDevice *device)
{
- const int fulldelay = (int) ((((Uint64) device->sample_frames) * 1000) / device->spec.freq);
- const int delay = SDL_max(fulldelay, 10);
+ const int sample_frames = device->sample_frames;
+ const int fulldelay = (int) ((((Uint64) sample_frames) * 1000) / device->spec.freq);
+ const int delay = SDL_clamp(fulldelay, 1, 5);
+ int total_delays = 0;
- while (!SDL_GetAtomicInt(&device->shutdown)) {
- const int rc = ALSA_snd_pcm_wait(device->hidden->pcm, delay);
- if (rc < 0 && (rc != -EAGAIN)) {
- const int status = ALSA_snd_pcm_recover(device->hidden->pcm, rc, 0);
- if (status < 0) {
- // Hmm, not much we can do - abort
- SDL_LogError(SDL_LOG_CATEGORY_AUDIO, "ALSA: snd_pcm_wait failed (unrecoverable): %s", ALSA_snd_strerror(rc));
- return false;
- }
- continue;
- }
+ SDL_assert(fulldelay > 0); // so the `fulldelay * 5` below produces a reasonable result.
- if (rc > 0) {
- break; // ready to go!
+ while (!SDL_GetAtomicInt(&device->shutdown) && (ALSA_snd_pcm_avail(device->hidden->pcm) < sample_frames)) {
+ if (total_delays >= (fulldelay * 5)) {
+ // Hmm, not much we can do - abort
+ SDL_LogError(SDL_LOG_CATEGORY_AUDIO, "ALSA: hardware seems to have frozen, giving up on it.");
+ return false;
+ } else {
+ SDL_Delay(delay);
+ total_delays += delay; // THIS IS NOT EXACT, but just so we don't wait forever on problems...
}
-
- // Timed out! Make sure we aren't shutting down and then wait again.
}
return true;
@@ -431,8 +427,11 @@ static int ALSA_RecordDevice(SDL_AudioDevice *device, void *buffer, int buflen)
SDL_assert((buflen % frame_size) == 0);
const snd_pcm_sframes_t total_available = ALSA_snd_pcm_avail(device->hidden->pcm);
- const int total_frames = SDL_min(buflen / frame_size, total_available);
+ if (total_available == 0) {
+ return 0; // go back to WaitDevice and try again.
+ }
+ const int total_frames = SDL_min(buflen / frame_size, total_available);
const int rc = ALSA_snd_pcm_readi(device->hidden->pcm, buffer, total_frames);
SDL_assert(rc != -EAGAIN); // assuming this can't happen if we used snd_pcm_wait and queried for available space. snd_pcm_recover won't handle it!