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)
+    return kSilenceDb;
+
+  return DoGetVolumeDb();
+}
+
+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;
+  DoSetVolumeDb(vol_db);
+}
+
+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) {

[davejcool, 2011/01/05 23:41:50]

Calling DoGetvolumeDb instead of the public GetVolumeDb since acquiring a lock
cannot be nested.

+      save_volume_ = DoGetVolumeDb();
+      DoSetVolumeDb(min_volume_);
+    } else {
+      DoSetVolumeDb(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;
+  }
+}
+

[davejcool, 2011/01/05 23:41:50]

Putting DoSet/DoGet here so it can be called when the lock is already being held
(e.g. from SetMute).

+double AudioMixerAlsa::DoGetVolumeDb() const {
+  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;
+}
+
+void AudioMixerAlsa::DoSetVolumeDb(double vol_db) {
+  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);
+  }
+}
+
+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
+