diff options
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/thinkpad-acpi.txt | 73 |
1 files changed, 45 insertions, 28 deletions
diff --git a/Documentation/thinkpad-acpi.txt b/Documentation/thinkpad-acpi.txt index ec499265deca..10c041ca13c7 100644 --- a/Documentation/thinkpad-acpi.txt +++ b/Documentation/thinkpad-acpi.txt @@ -1,7 +1,7 @@ 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> @@ -923,19 +923,34 @@ 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. -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: @@ -947,11 +962,11 @@ 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. @@ -961,17 +976,19 @@ there will be the following attributes: 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 |