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Diffstat (limited to 'Documentation/laptops/thinkpad-acpi.txt')
| -rw-r--r-- | Documentation/laptops/thinkpad-acpi.txt | 14 |
1 files changed, 8 insertions, 6 deletions
diff --git a/Documentation/laptops/thinkpad-acpi.txt b/Documentation/laptops/thinkpad-acpi.txt index 88fc0661de56..f2ff638cce8d 100644 --- a/Documentation/laptops/thinkpad-acpi.txt +++ b/Documentation/laptops/thinkpad-acpi.txt @@ -1169,17 +1169,19 @@ 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 UCMS (or CMOS). To select which one should be used, use the -brightness_mode module parameter: brightness_mode=1 selects EC mode, -brightness_mode=2 selects UCMS mode, brightness_mode=3 selects EC -mode with NVRAM backing (so that brightness changes are remembered -across shutdown/reboot). +For IBM ThinkPads, there are two interfaces to the firmware for direct +brightness control, EC and UCMS (or CMOS). To select which one should be +used, use the brightness_mode module parameter: brightness_mode=1 selects +EC mode, brightness_mode=2 selects UCMS mode, brightness_mode=3 selects EC +mode with NVRAM backing (so that brightness changes are remembered across +shutdown/reboot). The driver tries to select which interface to use from a table of defaults for each ThinkPad model. If it makes a wrong choice, please report this as a bug, so that we can fix it. +Lenovo ThinkPads only support brightness_mode=2 (UCMS). + 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 |