torvalds/linux

What:        /sys/class/backlight/<backlight>/bl_power
Date:        April 2005
KernelVersion:    2.6.12
Contact:    Richard Purdie <rpurdie@rpsys.net>
Description:
        Control BACKLIGHT power, values are FB_BLANK_* from fb.h

         - FB_BLANK_UNBLANK (0)   : power on.
         - FB_BLANK_POWERDOWN (4) : power off
Users:        HAL

What:        /sys/class/backlight/<backlight>/brightness
Date:        April 2005
KernelVersion:    2.6.12
Contact:    Richard Purdie <rpurdie@rpsys.net>
Description:
        Control the brightness for this <backlight>. Values
        are between 0 and max_brightness. This file will also
        show the brightness level stored in the driver, which
        may not be the actual brightness (see actual_brightness).
Users:        HAL

What:        /sys/class/backlight/<backlight>/actual_brightness
Date:        March 2006
KernelVersion:    2.6.17
Contact:    Richard Purdie <rpurdie@rpsys.net>
Description:
        Show the actual brightness by querying the hardware.
Users:        HAL

What:        /sys/class/backlight/<backlight>/max_brightness
Date:        April 2005
KernelVersion:    2.6.12
Contact:    Richard Purdie <rpurdie@rpsys.net>
Description:
        Maximum brightness for <backlight>.
Users:        HAL

What:        /sys/class/backlight/<backlight>/type
Date:        September 2010
KernelVersion:    2.6.37
Contact:    Matthew Garrett <mjg@redhat.com>
Description:
        The type of interface controlled by <backlight>.
        "firmware": The driver uses a standard firmware interface
        "platform": The driver uses a platform-specific interface
        "raw": The driver controls hardware registers directly

        In the general case, when multiple backlight
        interfaces are available for a single device, firmware
        control should be preferred to platform control should
        be preferred to raw control. Using a firmware
        interface reduces the probability of confusion with
        the hardware and the OS independently updating the
        backlight state. Platform interfaces are mostly a
        holdover from pre-standardisation of firmware
        interfaces.