[Qemu-devel] [PATCH] alsa broken when the host is suspended (or hibernated)

["Bjørn Mork" <bjorn@mork.no>]

audio output fails after resuming a host running a guest using alsa
audio output. Messages such as

 alsa: Failed to write 882 frames to 0x1804b98
 alsa: Reason: Streams pipe error

will appear repeatedly in the monitor.  This is caused by alsaaudio.c
not handling ESTRPIPE.  Fix this by calling snd_pcm_resume() on
ESTRPIPE.

This bug is similar to the vlc bug discussed on
https://trac.videolan.org/vlc/ticket/1286 and the fix is insired by
the patch attached to that bug report

Signed-off-by: Bjørn Mork <bjorn@mork.no>
---
 audio/alsaaudio.c |   22 ++++++++++++++++++++++
 1 files changed, 22 insertions(+), 0 deletions(-)

diff --git a/audio/alsaaudio.c b/audio/alsaaudio.c
index d0b7cd0..1c007e5 100644
--- a/audio/alsaaudio.c
+++ b/audio/alsaaudio.c
@@ -503,6 +503,16 @@ static int alsa_recover (snd_pcm_t *handle)
     return 0;
 }
 
+static int alsa_resume (snd_pcm_t *handle)
+{
+    int err = snd_pcm_resume (handle);
+    if (err < 0) {
+        alsa_logerr (err, "Failed to resume handle %p\n", handle);
+        return -1;
+    }
+    return 0;
+}
+
 static snd_pcm_sframes_t alsa_get_avail (snd_pcm_t *handle)
 {
     snd_pcm_sframes_t avail;
@@ -580,6 +590,18 @@ static int alsa_run_out (HWVoiceOut *hw)
                     }
                     continue;
 
+		case -ESTRPIPE:
+		    /* stream is suspended and waiting for an application recovery */
+		    if (alsa_resume (alsa->handle)) {
+                        alsa_logerr (written, "Failed to write %d frames\n",
+                                     len);
+                        goto exit;
+                    }
+                    if (conf.verbose) {
+                        dolog ("Resuming suspended stream\n");
+                    }
+                    continue;
+
                 case -EAGAIN:
                     goto exit;
 
-- 
1.5.6.5