Add ALSA support to volume keys

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 <alsa/asoundlib.h>
+
+#include "base/logging.h"
+#include "base/task.h"
+
+namespace chromeos {
+
+// Connect to the ALSA mixer using their simple element API.  Init is performed
+// asynchronously on the worker thread.
+//
+// To get a wider range and finer control over volume levels, first the Master
+// level is set, then if the PCM element exists, the total level is refined by
+// adjusting that as well.  If the PCM element has more volume steps, it allows
+// for finer granularity in the total volume.
+
+// TODO(davej): Serialize volume/mute to preserve settings when restarting.
+
+typedef long alsa_long_t;  // 'long' is required for ALSA API calls.
+
+namespace {
+
+const char* kMasterVolume = "Master";
+const char* kPCMVolume = "PCM";
+const double kDefaultMinVolume = -90.0;
+const double kDefaultMaxVolume = 0.0;
+
+}  // namespace
+
+AudioMixerAlsa::AudioMixerAlsa()
+    : min_volume_(kDefaultMinVolume),
+      max_volume_(kDefaultMaxVolume),
+      save_volume_(0),
+      mixer_state_(UNINITIALIZED),
+      alsa_mixer_(NULL),
+      elem_master_(NULL),
+      elem_pcm_(NULL) {
+}
+
+AudioMixerAlsa::~AudioMixerAlsa() {
+  FreeAlsaMixer();
+  if (thread_ != NULL) {
+    thread_->Stop();
+    thread_.reset();
+  }
+}
+
+bool AudioMixerAlsa::Init(InitDoneCallback* callback) {
+  if (!InitThread())
+    return false;
+
+  // Post the task of starting up, which can block for 200-500ms,
+  // so best not to do it on the caller's thread.
+  thread_->message_loop()->PostTask(FROM_HERE,
+      NewRunnableMethod(this, &AudioMixerAlsa::DoInit, callback));
+  return true;
+}
+
+bool AudioMixerAlsa::InitSync() {
+  if (!InitThread())
+    return false;
+  return InitializeAlsaMixer();
+}
+
+double AudioMixerAlsa::GetVolumeDb() const {
+  AutoLock lock(mixer_state_lock_);
+  if (mixer_state_ != READY)

[davejcool, 2011/01/05 21:31:07]

Changing to locking for the duration of the call.  The previous calls to
MixerReady() did not keep the lock held after the check, which could have caused
issues if shutting down before the function exited. These have been replaced
with an AutoLock for the duration of the function

+    return kSilenceDb;
+
+  double vol_total = 0.0;
+  GetElementVolume(elem_master_, &vol_total);
+
+  double vol_pcm = 0.0;
+  if (elem_pcm_ && (GetElementVolume(elem_pcm_, &vol_pcm)))
+    vol_total += vol_pcm;
+
+  return vol_total;
+}
+
+bool AudioMixerAlsa::GetVolumeLimits(double* vol_min, double* vol_max) {
+  AutoLock lock(mixer_state_lock_);
+  if (mixer_state_ != READY)
+    return false;
+  if (vol_min)
+    *vol_min = min_volume_;
+  if (vol_max)
+    *vol_max = max_volume_;
+  return true;
+}
+
+void AudioMixerAlsa::SetVolumeDb(double vol_db) {
+  AutoLock lock(mixer_state_lock_);
+  if (mixer_state_ != READY)
+    return;
+  double actual_vol = 0.0;
+
+  // If a PCM volume slider exists, then first set the Master volume to the
+  // nearest volume >= requested volume, then adjust PCM volume down to get
+  // closer to the requested volume.
+
+  if (elem_pcm_) {
+    SetElementVolume(elem_master_, vol_db, &actual_vol, 0.9999f);
+    SetElementVolume(elem_pcm_, vol_db - actual_vol, NULL, 0.5f);
+  } else {
+    SetElementVolume(elem_master_, vol_db, NULL, 0.5f);
+  }
+}
+
+bool AudioMixerAlsa::IsMute() const {
+  AutoLock lock(mixer_state_lock_);
+  if (mixer_state_ != READY)
+    return false;
+  return GetElementMuted(elem_master_);
+}
+
+void AudioMixerAlsa::SetMute(bool mute) {
+  AutoLock lock(mixer_state_lock_);
+  if (mixer_state_ != READY)
+    return;
+
+  // Set volume to minimum on mute, since switching the element off does not
+  // always mute as it should.
+
+  // TODO(davej): Setting volume to minimum can be removed once switching the
+  //              element off can be guaranteed to work.
+
+  bool old_value = GetElementMuted(elem_master_);
+
+  if (old_value != mute) {
+    if (mute) {
+      save_volume_ = GetVolumeDb();
+      SetVolumeDb(min_volume_);
+    } else {
+      SetVolumeDb(save_volume_);
+    }
+  }
+
+  SetElementMuted(elem_master_, mute);
+  if (elem_pcm_)
+    SetElementMuted(elem_pcm_, mute);
+}
+
+AudioMixer::State AudioMixerAlsa::CheckState() const {
+  AutoLock lock(mixer_state_lock_);
+  // If we think it's ready, verify it is actually so.
+  if ((mixer_state_ == READY) && (alsa_mixer_ == NULL))
+    mixer_state_ = IN_ERROR;
+  return mixer_state_;
+}
+
+////////////////////////////////////////////////////////////////////////////////
+// Private functions follow
+
+void AudioMixerAlsa::DoInit(InitDoneCallback* callback) {
+  bool success = InitializeAlsaMixer();
+
+  if (callback) {
+    callback->Run(success);
+    delete callback;
+  }
+}
+
+bool AudioMixerAlsa::InitThread() {
+  AutoLock lock(mixer_state_lock_);
+
+  if (mixer_state_ != UNINITIALIZED)
+    return false;
+
+  if (thread_ == NULL) {
+    thread_.reset(new base::Thread("AudioMixerAlsa"));
+    if (!thread_->Start()) {
+      thread_.reset();
+      return false;
+    }
+  }
+
+  mixer_state_ = INITIALIZING;
+  return true;
+}
+
+bool AudioMixerAlsa::InitializeAlsaMixer() {
+  AutoLock lock(mixer_state_lock_);
+  if (mixer_state_ != INITIALIZING)
+    return false;
+
+  int err;
+  snd_mixer_t* handle = NULL;
+  const char* card = "default";
+
+  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;
+  }
+
+  if ((err = snd_mixer_selem_register(handle, NULL, NULL)) < 0) {
+    LOG(ERROR) << "ALSA mixer register error: " << snd_strerror(err);
+    snd_mixer_close(handle);
+    return false;
+  }
+
+  if ((err = snd_mixer_load(handle)) < 0) {
+    LOG(ERROR) << "ALSA mixer " << card << " load error: %s"
+               << snd_strerror(err);
+    snd_mixer_close(handle);
+    return false;
+  }
+
+  VLOG(1) << "Opened ALSA mixer " << card << " OK";
+
+  elem_master_ = FindElementWithName(handle, kMasterVolume);
+  if (elem_master_) {
+    alsa_long_t long_lo, long_hi;
+    snd_mixer_selem_get_playback_dB_range(elem_master_, &long_lo, &long_hi);
+    min_volume_ = static_cast<double>(long_lo) / 100.0;
+    max_volume_ = static_cast<double>(long_hi) / 100.0;
+  } else {
+    LOG(ERROR) << "Cannot find 'Master' ALSA mixer element on " << card;
+    snd_mixer_close(handle);
+    return false;
+  }
+
+  elem_pcm_ = FindElementWithName(handle, kPCMVolume);
+  if (elem_pcm_) {
+    alsa_long_t long_lo, long_hi;
+    snd_mixer_selem_get_playback_dB_range(elem_pcm_, &long_lo, &long_hi);
+    min_volume_ += static_cast<double>(long_lo) / 100.0;
+    max_volume_ += static_cast<double>(long_hi) / 100.0;
+  }
+
+  VLOG(1) << "ALSA volume range is " << min_volume_ << " dB to "
+          << max_volume_ << " dB";
+
+  alsa_mixer_ = handle;
+  mixer_state_ = READY;
+  return true;
+}
+
+void AudioMixerAlsa::FreeAlsaMixer() {
+  AutoLock lock(mixer_state_lock_);
+  mixer_state_ = SHUTTING_DOWN;
+  if (alsa_mixer_) {
+    snd_mixer_close(alsa_mixer_);
+    alsa_mixer_ = NULL;
+  }
+}
+
+snd_mixer_elem_t* AudioMixerAlsa::FindElementWithName(
+    snd_mixer_t* handle,
+    const char* element_name) const {
+  snd_mixer_selem_id_t* sid;
+  snd_mixer_selem_id_alloca(&sid);
+  snd_mixer_selem_id_set_index(sid, 0);
+  snd_mixer_selem_id_set_name(sid, element_name);
+  snd_mixer_elem_t* elem = snd_mixer_find_selem(handle, sid);
+  if (!elem) {
+    LOG(ERROR) << "ALSA unable to find simple control "
+               << snd_mixer_selem_id_get_name(sid);
+  }
+  return elem;
+}
+
+bool AudioMixerAlsa::GetElementVolume(snd_mixer_elem_t* elem,
+                                      double* current_vol) const {
+  alsa_long_t long_vol = 0;
+  snd_mixer_selem_get_playback_dB(elem,
+                                  static_cast<snd_mixer_selem_channel_id_t>(0),
+                                  &long_vol);
+  *current_vol = static_cast<double>(long_vol) / 100.0;
+
+  return true;
+}
+
+bool AudioMixerAlsa::SetElementVolume(snd_mixer_elem_t* elem,
+                                      double new_vol,
+                                      double* actual_vol,
+                                      double rounding_bias) {
+  alsa_long_t vol_lo = 0;
+  alsa_long_t vol_hi = 0;
+  snd_mixer_selem_get_playback_volume_range(elem, &vol_lo, &vol_hi);
+  alsa_long_t vol_range = vol_hi - vol_lo;
+  if (vol_range <= 0)
+    return false;
+
+  alsa_long_t db_lo_int = 0;
+  alsa_long_t db_hi_int = 0;
+  snd_mixer_selem_get_playback_dB_range(elem, &db_lo_int, &db_hi_int);
+  double db_lo = static_cast<double>(db_lo_int) / 100.0;
+  double db_hi = static_cast<double>(db_hi_int) / 100.0;
+  double db_step = static_cast<double>(db_hi - db_lo) / vol_range;
+  if (db_step <= 0.0)
+    return false;
+
+  if (new_vol < db_lo)
+    new_vol = db_lo;
+
+  alsa_long_t value = static_cast<alsa_long_t>(rounding_bias +
+      (new_vol - db_lo) / db_step) + vol_lo;
+  snd_mixer_selem_set_playback_volume_all(elem, value);
+
+  VLOG(1) << "Set volume " << snd_mixer_selem_get_name(elem)
+          << " to " << new_vol << " ==> " << (value - vol_lo) * db_step + db_lo
+          << " dB";
+
+  if (actual_vol) {
+    alsa_long_t volume;
+    snd_mixer_selem_get_playback_volume(
+        elem,
+        static_cast<snd_mixer_selem_channel_id_t>(0),
+        &volume);
+    *actual_vol = db_lo + (volume - vol_lo) * db_step;
+
+    VLOG(1) << "Actual volume " << snd_mixer_selem_get_name(elem)
+            << " now " << *actual_vol << " dB";
+  }
+  return true;
+}
+
+bool AudioMixerAlsa::GetElementMuted(snd_mixer_elem_t* elem) const {
+  int enabled;
+  snd_mixer_selem_get_playback_switch(
+      elem,
+      static_cast<snd_mixer_selem_channel_id_t>(0),
+      &enabled);
+  return (enabled) ? false : true;
+}
+
+void AudioMixerAlsa::SetElementMuted(snd_mixer_elem_t* elem, bool mute) {
+  int enabled = mute ? 0 : 1;
+  snd_mixer_selem_set_playback_switch_all(elem, enabled);
+
+  VLOG(1) << "Set playback switch " << snd_mixer_selem_get_name(elem)
+          << " to " << enabled;
+}
+
+}  // namespace chromeos
+