What: /sys/class/backlight//bl_power Date: April 2005 KernelVersion: 2.6.12 Contact: Richard Purdie Description: Control BACKLIGHT power, values are compatible with FB_BLANK_* from fb.h - 0 (FB_BLANK_UNBLANK) : power on. - 4 (FB_BLANK_POWERDOWN) : power off Users: HAL What: /sys/class/backlight//brightness Date: April 2005 KernelVersion: 2.6.12 Contact: Richard Purdie Description: Control the brightness for this . 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//actual_brightness Date: March 2006 KernelVersion: 2.6.17 Contact: Richard Purdie Description: Show the actual brightness by querying the hardware. Due to implementation differences in hardware this may not match the value in 'brightness'. For example some hardware may treat blanking differently or have custom power saving features. Userspace should generally use the values in 'brightness' to make decisions. Users: HAL What: /sys/class/backlight//max_brightness Date: April 2005 KernelVersion: 2.6.12 Contact: Richard Purdie Description: Maximum brightness for . Users: HAL What: /sys/class/backlight//type Date: September 2010 KernelVersion: 2.6.37 Contact: Matthew Garrett Description: The type of interface controlled by . "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.