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-rw-r--r--Documentation/laptops/thinkpad-acpi.txt50
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diff --git a/Documentation/laptops/thinkpad-acpi.txt b/Documentation/laptops/thinkpad-acpi.txt
index 76cb428435d..a77da28a6f8 100644
--- a/Documentation/laptops/thinkpad-acpi.txt
+++ b/Documentation/laptops/thinkpad-acpi.txt
@@ -571,6 +571,47 @@ netlink interface and the input layer interface, and don't bother at all
with hotkey_report_mode.
+Brightness hotkey notes:
+
+These are the current sane choices for brightness key mapping in
+thinkpad-acpi:
+
+For IBM and Lenovo models *without* ACPI backlight control (the ones on
+which thinkpad-acpi will autoload its backlight interface by default,
+and on which ACPI video does not export a backlight interface):
+
+1. Don't enable or map the brightness hotkeys in thinkpad-acpi, as
+ these older firmware versions unfortunately won't respect the hotkey
+ mask for brightness keys anyway, and always reacts to them. This
+ usually work fine, unless X.org drivers are doing something to block
+ the BIOS. In that case, use (3) below. This is the default mode of
+ operation.
+
+2. Enable the hotkeys, but map them to something else that is NOT
+ KEY_BRIGHTNESS_UP/DOWN or any other keycode that would cause
+ userspace to try to change the backlight level, and use that as an
+ on-screen-display hint.
+
+3. IF AND ONLY IF X.org drivers find a way to block the firmware from
+ automatically changing the brightness, enable the hotkeys and map
+ them to KEY_BRIGHTNESS_UP and KEY_BRIGHTNESS_DOWN, and feed that to
+ something that calls xbacklight. thinkpad-acpi will not be able to
+ change brightness in that case either, so you should disable its
+ backlight interface.
+
+For Lenovo models *with* ACPI backlight control:
+
+1. Load up ACPI video and use that. ACPI video will report ACPI
+ events for brightness change keys. Do not mess with thinkpad-acpi
+ defaults in this case. thinkpad-acpi should not have anything to do
+ with backlight events in a scenario where ACPI video is loaded:
+ brightness hotkeys must be disabled, and the backlight interface is
+ to be kept disabled as well. This is the default mode of operation.
+
+2. Do *NOT* load up ACPI video, enable the hotkeys in thinkpad-acpi,
+ and map them to KEY_BRIGHTNESS_UP and KEY_BRIGHTNESS_DOWN. Process
+ these keys on userspace somehow (e.g. by calling xbacklight).
+
Bluetooth
---------
@@ -1090,6 +1131,15 @@ it there will be the following attributes:
dim the display.
+WARNING:
+
+ Whatever you do, do NOT ever call thinkpad-acpi backlight-level change
+ interface and the ACPI-based backlight level change interface
+ (available on newer BIOSes, and driven by the Linux ACPI video driver)
+ at the same time. The two will interact in bad ways, do funny things,
+ and maybe reduce the life of the backlight lamps by needlessly kicking
+ its level up and down at every change.
+
Volume control -- /proc/acpi/ibm/volume
---------------------------------------