alsa: work around slightly broken _delay implementations

Use snd_pcm_avail_delay() in pa_alsa_safe_delay() so that we can check the delay
value against the avail value and patch it up when it looks invalid. Only do
this for capture.

4 files changed, 46 insertions, 6 deletions

diff --git a/src/modules/alsa/alsa-sink.c b/src/modules/alsa/alsa-sink.c
index 4a5fe3fb..ae7fecd2 100644
--- a/src/modules/alsa/alsa-sink.c
+++ b/src/modules/alsa/alsa-sink.c
@@ -803,7 +803,7 @@ static void update_smoother(struct userdata *u) {
 
     /* Let's update the time smoother */
 
-    if (PA_UNLIKELY((err = pa_alsa_safe_delay(u->pcm_handle, &delay, u->hwbuf_size, &u->sink->sample_spec)) < 0)) {
+    if (PA_UNLIKELY((err = pa_alsa_safe_delay(u->pcm_handle, &delay, u->hwbuf_size, &u->sink->sample_spec, FALSE)) < 0)) {
         pa_log_warn("Failed to query DSP status data: %s", pa_alsa_strerror(err));
         return;
     }
diff --git a/src/modules/alsa/alsa-source.c b/src/modules/alsa/alsa-source.c
index 8b2cee50..10f0d74e 100644
--- a/src/modules/alsa/alsa-source.c
+++ b/src/modules/alsa/alsa-source.c
@@ -760,7 +760,7 @@ static void update_smoother(struct userdata *u) {
 
     /* Let's update the time smoother */
 
-    if (PA_UNLIKELY((err = pa_alsa_safe_delay(u->pcm_handle, &delay, u->hwbuf_size, &u->source->sample_spec)) < 0)) {
+    if (PA_UNLIKELY((err = pa_alsa_safe_delay(u->pcm_handle, &delay, u->hwbuf_size, &u->source->sample_spec, TRUE)) < 0)) {
         pa_log_warn("Failed to get delay: %s", pa_alsa_strerror(err));
         return;
     }
diff --git a/src/modules/alsa/alsa-util.c b/src/modules/alsa/alsa-util.c
index 1cbb3f31..2d0d3563 100644
--- a/src/modules/alsa/alsa-util.c
+++ b/src/modules/alsa/alsa-util.c
@@ -1125,10 +1125,11 @@ snd_pcm_sframes_t pa_alsa_safe_avail(snd_pcm_t *pcm, size_t hwbuf_size, const pa
     return n;
 }
 
-int pa_alsa_safe_delay(snd_pcm_t *pcm, snd_pcm_sframes_t *delay, size_t hwbuf_size, const pa_sample_spec *ss) {
+int pa_alsa_safe_delay(snd_pcm_t *pcm, snd_pcm_sframes_t *delay, size_t hwbuf_size, const pa_sample_spec *ss, pa_bool_t capture) {
     ssize_t k;
     size_t abs_k;
     int r;
+    snd_pcm_sframes_t avail = 0;
 
     pa_assert(pcm);
     pa_assert(delay);
@@ -1136,9 +1137,10 @@ int pa_alsa_safe_delay(snd_pcm_t *pcm, snd_pcm_sframes_t *delay, size_t hwbuf_si
     pa_assert(ss);
 
     /* Some ALSA driver expose weird bugs, let's inform the user about
-     * what is going on */
+     * what is going on. We're going to get both the avail and delay values so
+     * that we can compare and check them for capture */
 
-    if ((r = snd_pcm_delay(pcm, delay)) < 0)
+    if ((r = snd_pcm_avail_delay(pcm, &avail, delay)) < 0)
         return r;
 
     k = (ssize_t) *delay * (ssize_t) pa_frame_size(ss);
@@ -1167,6 +1169,44 @@ int pa_alsa_safe_delay(snd_pcm_t *pcm, snd_pcm_sframes_t *delay, size_t hwbuf_si
             *delay = (snd_pcm_sframes_t) (hwbuf_size / pa_frame_size(ss));
     }
 
+    if (capture) {
+        abs_k = (size_t) avail * pa_frame_size(ss);
+
+        if (abs_k >= hwbuf_size * 5 ||
+            abs_k >= pa_bytes_per_second(ss)*10) {
+
+            PA_ONCE_BEGIN {
+                char *dn = pa_alsa_get_driver_name_by_pcm(pcm);
+                pa_log(_("snd_pcm_avail() returned a value that is exceptionally large: %lu bytes (%lu ms).\n"
+                         "Most likely this is a bug in the ALSA driver '%s'. Please report this issue to the ALSA developers."),
+                       (unsigned long) k,
+                       (unsigned long) (pa_bytes_to_usec(k, ss) / PA_USEC_PER_MSEC),
+                       pa_strnull(dn));
+                pa_xfree(dn);
+                pa_alsa_dump(PA_LOG_ERROR, pcm);
+            } PA_ONCE_END;
+
+            /* Mhmm, let's try not to fail completely */
+            avail = (snd_pcm_sframes_t) (hwbuf_size / pa_frame_size(ss));
+        }
+
+        if (*delay < avail) {
+            PA_ONCE_BEGIN {
+                char *dn = pa_alsa_get_driver_name_by_pcm(pcm);
+                pa_log(_("snd_pcm_avail_delay() returned strange values: delay %lu is less than avail %lu.\n"
+                         "Most likely this is a bug in the ALSA driver '%s'. Please report this issue to the ALSA developers."),
+                       (unsigned long) *delay,
+                       (unsigned long) avail,
+                       pa_strnull(dn));
+                pa_xfree(dn);
+                pa_alsa_dump(PA_LOG_ERROR, pcm);
+            } PA_ONCE_END;
+
+            /* try to fixup */
+            *delay = avail;
+        }
+    }
+
     return 0;
 }
 
diff --git a/src/modules/alsa/alsa-util.h b/src/modules/alsa/alsa-util.h
index 1d1256bd..9e29fd46 100644
--- a/src/modules/alsa/alsa-util.h
+++ b/src/modules/alsa/alsa-util.h
@@ -129,7 +129,7 @@ int pa_alsa_recover_from_poll(snd_pcm_t *pcm, int revents);
 pa_rtpoll_item* pa_alsa_build_pollfd(snd_pcm_t *pcm, pa_rtpoll *rtpoll);
 
 snd_pcm_sframes_t pa_alsa_safe_avail(snd_pcm_t *pcm, size_t hwbuf_size, const pa_sample_spec *ss);
-int pa_alsa_safe_delay(snd_pcm_t *pcm, snd_pcm_sframes_t *delay, size_t hwbuf_size, const pa_sample_spec *ss);
+int pa_alsa_safe_delay(snd_pcm_t *pcm, snd_pcm_sframes_t *delay, size_t hwbuf_size, const pa_sample_spec *ss, pa_bool_t capture);
 int pa_alsa_safe_mmap_begin(snd_pcm_t *pcm, const snd_pcm_channel_area_t **areas, snd_pcm_uframes_t *offset, snd_pcm_uframes_t *frames, size_t hwbuf_size, const pa_sample_spec *ss);
 
 char *pa_alsa_get_driver_name(int card);