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authorHenrique de Moraes Holschuh <hmh@hmh.eng.br>2007-07-18 23:45:43 -0300
committerLen Brown <len.brown@intel.com>2007-07-21 23:49:03 -0400
commit24d3b77467b6aaf59e38dce4aa86d05541858195 (patch)
tree92975c9c2d4b37922d25782bd02d7076d77e817e /Documentation
parentd5a2f2f1d68e2da538ac28540cddd9ccc733b001 (diff)
downloadop-kernel-dev-24d3b77467b6aaf59e38dce4aa86d05541858195.zip
op-kernel-dev-24d3b77467b6aaf59e38dce4aa86d05541858195.tar.gz
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')
-rw-r--r--Documentation/thinkpad-acpi.txt6
1 files changed, 6 insertions, 0 deletions
diff --git a/Documentation/thinkpad-acpi.txt b/Documentation/thinkpad-acpi.txt
index c670363..c145bcc 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.
+
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