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-rw-r--r--Documentation/laptops/thinkpad-acpi.txt13
1 files changed, 13 insertions, 0 deletions
diff --git a/Documentation/laptops/thinkpad-acpi.txt b/Documentation/laptops/thinkpad-acpi.txt
index bd87682103c1..6a5814330e51 100644
--- a/Documentation/laptops/thinkpad-acpi.txt
+++ b/Documentation/laptops/thinkpad-acpi.txt
@@ -1097,6 +1097,18 @@ Volume control
1097 1097
1098procfs: /proc/acpi/ibm/volume 1098procfs: /proc/acpi/ibm/volume
1099 1099
1100NOTE: by default, the volume control interface operates in read-only
1101mode, as it is supposed to be used for on-screen-display purposes.
1102The read/write mode can be enabled through the use of the
1103"volume_control=1" module parameter.
1104
1105NOTE: distros are urged to not enable volume_control by default, this
1106should be done by the local admin only. The ThinkPad UI is for the
1107console audio control to be done through the volume keys only, and for
1108the desktop environment to just provide on-screen-display feedback.
1109Software volume control should be done only in the main AC97/HDA
1110mixer.
1111
1100This feature allows volume control on ThinkPad models with a digital 1112This feature allows volume control on ThinkPad models with a digital
1101volume knob (when available, not all models have it), as well as 1113volume knob (when available, not all models have it), as well as
1102mute/unmute control. The available commands are: 1114mute/unmute control. The available commands are:
@@ -1465,3 +1477,4 @@ Sysfs interface changelog:
14650x020600: Marker for backlight change event support. 14770x020600: Marker for backlight change event support.
1466 1478
14670x020700: Support for mute-only mixers. 14790x020700: Support for mute-only mixers.
1480 Volume control in read-only mode by default.