1 files changed, 35 insertions, 26 deletions

diff --git a/Documentation/thinkpad-acpi.txt b/Documentation/thinkpad-acpi.txt
index ec499265deca..a743bfa62b95 100644
--- a/Documentation/thinkpad-acpi.txt
+++ b/Documentation/thinkpad-acpi.txt
@@ -923,19 +923,26 @@ 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.
 
 Procfs notes:
 
@@ -947,11 +954,11 @@ 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 +968,19 @@ 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