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Diffstat (limited to 'Documentation/thinkpad-acpi.txt')
| -rw-r--r-- | Documentation/thinkpad-acpi.txt | 52 |
1 files changed, 46 insertions, 6 deletions
diff --git a/Documentation/thinkpad-acpi.txt b/Documentation/thinkpad-acpi.txt index 352e8aee63f..eab4997efc0 100644 --- a/Documentation/thinkpad-acpi.txt +++ b/Documentation/thinkpad-acpi.txt @@ -611,19 +611,59 @@ registers contain the current battery capacity, etc. If you experiment with this, do send me your results (including some complete dumps with a description of the conditions when they were taken.) -LCD brightness control -- /proc/acpi/ibm/brightness ---------------------------------------------------- +LCD brightness control +---------------------- + +procfs: /proc/acpi/ibm/brightness +sysfs backlight device "thinkpad_screen" This feature allows software control of the LCD brightness on ThinkPad -models which don't have a hardware brightness slider. The available -commands are: +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. + +Procfs notes: + + The available commands are: echo up >/proc/acpi/ibm/brightness echo down >/proc/acpi/ibm/brightness echo 'level <level>' >/proc/acpi/ibm/brightness -The <level> number range is 0 to 7, although not all of them may be -distinct. The current brightness level is shown in the file. +Sysfs notes: + +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: + + max_brightness: + Reads the maximum brightness the hardware can be set to. + The minimum is always zero. + + actual_brightness: + 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. + + 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. + Volume control -- /proc/acpi/ibm/volume --------------------------------------- |