ThinkPad ACPI Extras Driver
- Version 0.16
- August 2nd, 2007
+ Version 0.17
+ October 04th, 2007
Borislav Deianov <borislav@users.sf.net>
Henrique de Moraes Holschuh <hmh@hmh.eng.br>
This feature allows software control of the LCD brightness on ThinkPad
models which don't have a hardware brightness slider.
-It has some limitations: the LCD backlight cannot be actually turned on or off
-by this interface, and in many ThinkPad models, the "dim while on battery"
-functionality will be enabled by the BIOS when this interface is used, and
-cannot be controlled.
-
-The backlight control has eight levels, ranging from 0 to 7. Some of the
-levels may not be distinct.
-
-There are two interfaces to the firmware for brightness control, EC and CMOS.
-To select which one should be used, use the brightness_mode module parameter:
-brightness_mode=1 selects EC mode, brightness_mode=2 selects CMOS mode,
-brightness_mode=3 selects both EC and CMOS. The driver tries to autodetect
-which interface to use.
+It has some limitations: the LCD backlight cannot be actually turned on or
+off by this interface, and in many ThinkPad models, the "dim while on
+battery" functionality will be enabled by the BIOS when this interface is
+used, and cannot be controlled.
+
+On IBM (and some of the earlier Lenovo) ThinkPads, the backlight control
+has eight brightness levels, ranging from 0 to 7. Some of the levels
+may not be distinct. Later Lenovo models that implement the ACPI
+display backlight brightness control methods have 16 levels, ranging
+from 0 to 15.
+
+There are two interfaces to the firmware for direct brightness control,
+EC and CMOS. To select which one should be used, use the
+brightness_mode module parameter: brightness_mode=1 selects EC mode,
+brightness_mode=2 selects CMOS mode, brightness_mode=3 selects both EC
+and CMOS. The driver tries to autodetect which interface to use.
+
+When display backlight brightness controls are available through the
+standard ACPI interface, it is best to use it instead of this direct
+ThinkPad-specific interface. The driver will disable its native
+backlight brightness control interface if it detects that the standard
+ACPI interface is available in the ThinkPad.
+
+The brightness_enable module parameter can be used to control whether
+the LCD brightness control feature will be enabled when available.
+brightness_enable=0 forces it to be disabled. brightness_enable=1
+forces it to be enabled when available, even if the standard ACPI
+interface is also available.
Procfs notes:
Sysfs notes:
-The interface is implemented through the backlight sysfs class, which is poorly
-documented at this time.
+The interface is implemented through the backlight sysfs class, which is
+poorly documented at this time.
-Locate the thinkpad_screen device under /sys/class/backlight, and inside it
-there will be the following attributes:
+Locate the thinkpad_screen device under /sys/class/backlight, and inside
+it there will be the following attributes:
max_brightness:
Reads the maximum brightness the hardware can be set to.
Reads what brightness the screen is set to at this instant.
brightness:
- Writes request the driver to change brightness to the given
- value. Reads will tell you what brightness the driver is trying
- to set the display to when "power" is set to zero and the display
- has not been dimmed by a kernel power management event.
+ Writes request the driver to change brightness to the
+ given value. Reads will tell you what brightness the
+ driver is trying to set the display to when "power" is set
+ to zero and the display has not been dimmed by a kernel
+ power management event.
power:
- power management mode, where 0 is "display on", and 1 to 3 will
- dim the display backlight to brightness level 0 because
- thinkpad-acpi cannot really turn the backlight off. Kernel
- power management events can temporarily increase the current
- power management level, i.e. they can dim the display.
+ power management mode, where 0 is "display on", and 1 to 3
+ will dim the display backlight to brightness level 0
+ because thinkpad-acpi cannot really turn the backlight
+ off. Kernel power management events can temporarily
+ increase the current power management level, i.e. they can
+ dim the display.
Volume control -- /proc/acpi/ibm/volume
An enabled fan in level "auto" may stop spinning if the EC decides the
ThinkPad is cool enough and doesn't need the extra airflow. This is
-normal, and the EC will spin the fan up if the varios thermal readings
+normal, and the EC will spin the fan up if the various thermal readings
rise too much.
On the X40, this seems to depend on the CPU and HDD temperatures.
Enabling debugging output
-------------------------
-The module takes a debug paramater which can be used to selectively
+The module takes a debug parameter which can be used to selectively
enable various classes of debugging output, for example:
modprobe ibm_acpi debug=0xffff
git.openpandora.org / pandora-kernel.git / blobdiff