aboutsummaryrefslogtreecommitdiffstats
path: root/Documentation/laptops
diff options
context:
space:
mode:
authorHenrique de Moraes Holschuh <hmh@hmh.eng.br>2009-12-26 19:52:16 -0500
committerLen Brown <len.brown@intel.com>2009-12-26 22:37:58 -0500
commit169220f88f0f26f4450ac0bc8ff0f807b453ec58 (patch)
treedbed22d9aaacd2deddc796771b9f4c5129db55ff /Documentation/laptops
parentff850c339a1a6a7724537160c73cdc09a483fc5d (diff)
thinkpad-acpi: update volume subdriver documentation
Signed-off-by: Henrique de Moraes Holschuh <hmh@hmh.eng.br> Signed-off-by: Len Brown <len.brown@intel.com>
Diffstat (limited to 'Documentation/laptops')
-rw-r--r--Documentation/laptops/thinkpad-acpi.txt58
1 files changed, 50 insertions, 8 deletions
diff --git a/Documentation/laptops/thinkpad-acpi.txt b/Documentation/laptops/thinkpad-acpi.txt
index 169091f75e6d..75afa1229fd7 100644
--- a/Documentation/laptops/thinkpad-acpi.txt
+++ b/Documentation/laptops/thinkpad-acpi.txt
@@ -1092,8 +1092,8 @@ WARNING:
1092 its level up and down at every change. 1092 its level up and down at every change.
1093 1093
1094 1094
1095Volume control 1095Volume control (Console Audio control)
1096-------------- 1096--------------------------------------
1097 1097
1098procfs: /proc/acpi/ibm/volume 1098procfs: /proc/acpi/ibm/volume
1099ALSA: "ThinkPad Console Audio Control", default ID: "ThinkPadEC" 1099ALSA: "ThinkPad Console Audio Control", default ID: "ThinkPadEC"
@@ -1110,9 +1110,53 @@ the desktop environment to just provide on-screen-display feedback.
1110Software volume control should be done only in the main AC97/HDA 1110Software volume control should be done only in the main AC97/HDA
1111mixer. 1111mixer.
1112 1112
1113This feature allows volume control on ThinkPad models with a digital 1113
1114volume knob (when available, not all models have it), as well as 1114About the ThinkPad Console Audio control:
1115mute/unmute control. The available commands are: 1115
1116ThinkPads have a built-in amplifier and muting circuit that drives the
1117console headphone and speakers. This circuit is after the main AC97
1118or HDA mixer in the audio path, and under exclusive control of the
1119firmware.
1120
1121ThinkPads have three special hotkeys to interact with the console
1122audio control: volume up, volume down and mute.
1123
1124It is worth noting that the normal way the mute function works (on
1125ThinkPads that do not have a "mute LED") is:
1126
11271. Press mute to mute. It will *always* mute, you can press it as
1128 many times as you want, and the sound will remain mute.
1129
11302. Press either volume key to unmute the ThinkPad (it will _not_
1131 change the volume, it will just unmute).
1132
1133This is a very superior design when compared to the cheap software-only
1134mute-toggle solution found on normal consumer laptops: you can be
1135absolutely sure the ThinkPad will not make noise if you press the mute
1136button, no matter the previous state.
1137
1138The IBM ThinkPads, and the earlier Lenovo ThinkPads have variable-gain
1139amplifiers driving the speakers and headphone output, and the firmware
1140also handles volume control for the headphone and speakers on these
1141ThinkPads without any help from the operating system (this volume
1142control stage exists after the main AC97 or HDA mixer in the audio
1143path).
1144
1145The newer Lenovo models only have firmware mute control, and depend on
1146the main HDA mixer to do volume control (which is done by the operating
1147system). In this case, the volume keys are filtered out for unmute
1148key press (there are some firmware bugs in this area) and delivered as
1149normal key presses to the operating system (thinkpad-acpi is not
1150involved).
1151
1152
1153The ThinkPad-ACPI volume control:
1154
1155The preferred way to interact with the Console Audio control is the
1156ALSA interface.
1157
1158The legacy procfs interface allows one to read the current state,
1159and if volume control is enabled, accepts the following commands:
1116 1160
1117 echo up >/proc/acpi/ibm/volume 1161 echo up >/proc/acpi/ibm/volume
1118 echo down >/proc/acpi/ibm/volume 1162 echo down >/proc/acpi/ibm/volume
@@ -1121,12 +1165,10 @@ mute/unmute control. The available commands are:
1121 echo 'level <level>' >/proc/acpi/ibm/volume 1165 echo 'level <level>' >/proc/acpi/ibm/volume
1122 1166
1123The <level> number range is 0 to 14 although not all of them may be 1167The <level> number range is 0 to 14 although not all of them may be
1124distinct. The unmute the volume after the mute command, use either the 1168distinct. To unmute the volume after the mute command, use either the
1125up or down command (the level command will not unmute the volume), or 1169up or down command (the level command will not unmute the volume), or
1126the unmute command. 1170the unmute command.
1127 1171
1128The current volume level and mute state is shown in the file.
1129
1130You can use the volume_capabilities parameter to tell the driver 1172You can use the volume_capabilities parameter to tell the driver
1131whether your thinkpad has volume control or mute-only control: 1173whether your thinkpad has volume control or mute-only control:
1132volume_capabilities=1 for mixers with mute and volume control, 1174volume_capabilities=1 for mixers with mute and volume control,