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There may be multiple ways of controlling the backlight on a given machine. Allow drivers to expose the type of interface they are providing, making it possible for userspace to make appropriate policy decisions. Signed-off-by: Matthew Garrett <mjg@redhat.com> Cc: Richard Purdie <rpurdie@rpsys.net> Cc: Chris Wilson <chris@chris-wilson.co.uk> Cc: David Airlie <airlied@linux.ie> Cc: Alex Deucher <alexdeucher@gmail.com> Cc: Ben Skeggs <bskeggs@redhat.com> Cc: Zhang Rui <rui.zhang@intel.com> Cc: Len Brown <lenb@kernel.org> Cc: Jesse Barnes <jbarnes@virtuousgeek.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
57 lines
1.9 KiB
Plaintext
57 lines
1.9 KiB
Plaintext
What: /sys/class/backlight/<backlight>/bl_power
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Date: April 2005
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KernelVersion: 2.6.12
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Contact: Richard Purdie <rpurdie@rpsys.net>
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Description:
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Control BACKLIGHT power, values are FB_BLANK_* from fb.h
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- FB_BLANK_UNBLANK (0) : power on.
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- FB_BLANK_POWERDOWN (4) : power off
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Users: HAL
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What: /sys/class/backlight/<backlight>/brightness
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Date: April 2005
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KernelVersion: 2.6.12
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Contact: Richard Purdie <rpurdie@rpsys.net>
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Description:
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Control the brightness for this <backlight>. Values
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are between 0 and max_brightness. This file will also
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show the brightness level stored in the driver, which
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may not be the actual brightness (see actual_brightness).
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Users: HAL
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What: /sys/class/backlight/<backlight>/actual_brightness
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Date: March 2006
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KernelVersion: 2.6.17
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Contact: Richard Purdie <rpurdie@rpsys.net>
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Description:
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Show the actual brightness by querying the hardware.
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Users: HAL
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What: /sys/class/backlight/<backlight>/max_brightness
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Date: April 2005
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KernelVersion: 2.6.12
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Contact: Richard Purdie <rpurdie@rpsys.net>
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Description:
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Maximum brightness for <backlight>.
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Users: HAL
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What: /sys/class/backlight/<backlight>/type
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Date: September 2010
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KernelVersion: 2.6.37
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Contact: Matthew Garrett <mjg@redhat.com>
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Description:
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The type of interface controlled by <backlight>.
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"firmware": The driver uses a standard firmware interface
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"platform": The driver uses a platform-specific interface
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"raw": The driver controls hardware registers directly
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In the general case, when multiple backlight
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interfaces are available for a single device, firmware
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control should be preferred to platform control should
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be preferred to raw control. Using a firmware
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interface reduces the probability of confusion with
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the hardware and the OS independently updating the
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backlight state. Platform interfaces are mostly a
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holdover from pre-standardisation of firmware
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interfaces.
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