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| author | Henrique de Moraes Holschuh <hmh@hmh.eng.br> | 2007-07-18 23:45:43 -0300 |
|---|---|---|
| committer | Len Brown <len.brown@intel.com> | 2007-07-21 23:49:03 -0400 |
| commit | 24d3b77467b6aaf59e38dce4aa86d05541858195 (patch) | |
| tree | 92975c9c2d4b37922d25782bd02d7076d77e817e /Documentation/thinkpad-acpi.txt | |
| parent | d5a2f2f1d68e2da538ac28540cddd9ccc733b001 (diff) | |
| download | lwn-24d3b77467b6aaf59e38dce4aa86d05541858195.tar.gz lwn-24d3b77467b6aaf59e38dce4aa86d05541858195.zip | |
ACPI: thinkpad-acpi: allow use of CMOS NVRAM for brightness control
It appears that Lenovo decided to break the EC brightness control interface
in a weird way in their latest BIOSes. Fortunately, the old CMOS NVRAM
interface works just fine in such BIOSes.
Add a module parameter that allows the user to select which strategy to use
for brightness control: EC, NVRAM, or both. By default, do both (which is
the way thinkpad-acpi used to work until now) on IBM ThinkPads, and use
NVRAM only on Lenovo ThinkPads.
Signed-off-by: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
Signed-off-by: Len Brown <len.brown@intel.com>
Diffstat (limited to 'Documentation/thinkpad-acpi.txt')
| -rw-r--r-- | Documentation/thinkpad-acpi.txt | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/Documentation/thinkpad-acpi.txt b/Documentation/thinkpad-acpi.txt index c670363cf5a4..c145bcce2339 100644 --- a/Documentation/thinkpad-acpi.txt +++ b/Documentation/thinkpad-acpi.txt @@ -860,6 +860,12 @@ 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. + Procfs notes: The available commands are: |