Mute ALSA audio completely

chrome/browser/chromeos/audio_mixer_alsa.cc

 // Copyright (c) 2010 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/chromeos/audio_mixer_alsa.h"
 
 #include <cmath>
 
 #include <alsa/asoundlib.h>
 
@@ skipping 228 matching lines @@
 
 bool AudioMixerAlsa::InitializeAlsaMixer() {
   base::AutoLock lock(mixer_state_lock_);
   if (mixer_state_ != INITIALIZING)
     return false;
 
   int err;
   snd_mixer_t* handle = NULL;
   const char* card = "default";
 
+  PingPCM();

[scherkus (not reviewing), 2011/03/02 19:07:11]

maybe inline this code considering it's not caleld anywhere else and you already
have a bunch of snd_XXX_YYY() functions + error checking + logging

[davejcool, 2011/03/03 20:05:02]

It is remarkably close to the other calls in InitializeAlsaMixer(), so I'm now
inlining instead.

+
   if ((err = snd_mixer_open(&handle, 0)) < 0) {
     LOG(ERROR) << "ALSA mixer " << card << " open error: " << snd_strerror(err);
     return false;
   }
 
   if ((err = snd_mixer_attach(handle, card)) < 0) {
     LOG(ERROR) << "ALSA Attach to card " << card << " failed: "
                << snd_strerror(err);
     snd_mixer_close(handle);
     return false;
@@ skipping 253 matching lines @@
   int alsa_result = snd_mixer_selem_set_playback_switch_all(elem, enabled);
   if (alsa_result != 0) {
     LOG(WARNING) << "snd_mixer_selem_set_playback_switch_all() failed: "
                  << snd_strerror(alsa_result);
   } else {
     VLOG(1) << "Set playback switch " << snd_mixer_selem_get_name(elem)
             << " to " << enabled;
   }
 }
 
+void AudioMixerAlsa::PingPCM() {
+  snd_pcm_t* pcm_out_handle;
+  int err;
+  if ((err = snd_pcm_open(&pcm_out_handle,
+                          "default",
+                          SND_PCM_STREAM_PLAYBACK,
+                          0)) >= 0) {
+    snd_pcm_close(pcm_out_handle);
+    return;
+  }
+  LOG(ERROR) << "ALSA PCM open error: " << snd_strerror(err);
+}
+
 }  // namespace chromeos