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-rw-r--r--Documentation/laptops/thinkpad-acpi.txt12
1 files changed, 9 insertions, 3 deletions
diff --git a/Documentation/laptops/thinkpad-acpi.txt b/Documentation/laptops/thinkpad-acpi.txt
index 25ed43d0a21f..3d7650768bb5 100644
--- a/Documentation/laptops/thinkpad-acpi.txt
+++ b/Documentation/laptops/thinkpad-acpi.txt
@@ -1157,10 +1157,15 @@ display backlight brightness control methods have 16 levels, ranging
1157from 0 to 15. 1157from 0 to 15.
1158 1158
1159There are two interfaces to the firmware for direct brightness control, 1159There are two interfaces to the firmware for direct brightness control,
1160EC and CMOS. To select which one should be used, use the 1160EC and UCMS (or CMOS). To select which one should be used, use the
1161brightness_mode module parameter: brightness_mode=1 selects EC mode, 1161brightness_mode module parameter: brightness_mode=1 selects EC mode,
1162brightness_mode=2 selects CMOS mode, brightness_mode=3 selects both EC 1162brightness_mode=2 selects UCMS mode, brightness_mode=3 selects EC
1163and CMOS. The driver tries to auto-detect which interface to use. 1163mode with NVRAM backing (so that brightness changes are remembered
1164across shutdown/reboot).
1165
1166The driver tries to select which interface to use from a table of
1167defaults for each ThinkPad model. If it makes a wrong choice, please
1168report this as a bug, so that we can fix it.
1164 1169
1165When display backlight brightness controls are available through the 1170When display backlight brightness controls are available through the
1166standard ACPI interface, it is best to use it instead of this direct 1171standard ACPI interface, it is best to use it instead of this direct
@@ -1498,6 +1503,7 @@ to enable more than one output class, just add their values.
1498 (bluetooth, WWAN, UWB...) 1503 (bluetooth, WWAN, UWB...)
1499 0x0008 HKEY event interface, hotkeys 1504 0x0008 HKEY event interface, hotkeys
1500 0x0010 Fan control 1505 0x0010 Fan control
1506 0x0020 Backlight brightness
1501 1507
1502There is also a kernel build option to enable more debugging 1508There is also a kernel build option to enable more debugging
1503information, which may be necessary to debug driver problems. 1509information, which may be necessary to debug driver problems.