1What: /sys/class/backlight/<backlight>/bl_power 2Date: April 2005 3KernelVersion: 2.6.12 4Contact: Richard Purdie <rpurdie@rpsys.net> 5Description: 6 Control BACKLIGHT power, values are compatible with 7 FB_BLANK_* from fb.h 8 9 - 0 (FB_BLANK_UNBLANK) : power on. 10 - 4 (FB_BLANK_POWERDOWN) : power off 11Users: HAL 12 13What: /sys/class/backlight/<backlight>/brightness 14Date: April 2005 15KernelVersion: 2.6.12 16Contact: Richard Purdie <rpurdie@rpsys.net> 17Description: 18 Control the brightness for this <backlight>. Values 19 are between 0 and max_brightness. This file will also 20 show the brightness level stored in the driver, which 21 may not be the actual brightness (see actual_brightness). 22Users: HAL 23 24What: /sys/class/backlight/<backlight>/actual_brightness 25Date: March 2006 26KernelVersion: 2.6.17 27Contact: Richard Purdie <rpurdie@rpsys.net> 28Description: 29 Show the actual brightness by querying the hardware. Due 30 to implementation differences in hardware this may not 31 match the value in 'brightness'. For example some hardware 32 may treat blanking differently or have custom power saving 33 features. Userspace should generally use the values in 34 'brightness' to make decisions. 35Users: HAL 36 37What: /sys/class/backlight/<backlight>/max_brightness 38Date: April 2005 39KernelVersion: 2.6.12 40Contact: Richard Purdie <rpurdie@rpsys.net> 41Description: 42 Maximum brightness for <backlight>. 43Users: HAL 44 45What: /sys/class/backlight/<backlight>/type 46Date: September 2010 47KernelVersion: 2.6.37 48Contact: Matthew Garrett <mjg@redhat.com> 49Description: 50 The type of interface controlled by <backlight>. 51 "firmware": The driver uses a standard firmware interface 52 "platform": The driver uses a platform-specific interface 53 "raw": The driver controls hardware registers directly 54 55 In the general case, when multiple backlight 56 interfaces are available for a single device, firmware 57 control should be preferred to platform control should 58 be preferred to raw control. Using a firmware 59 interface reduces the probability of confusion with 60 the hardware and the OS independently updating the 61 backlight state. Platform interfaces are mostly a 62 holdover from pre-standardisation of firmware 63 interfaces. 64