a1cacb8a8e
Duplicate FB_BLANK_ constants as BACKLIGHT_POWER__ constants in the backlight header file. Allows backlight drivers to avoid including the fbdev header file and removes a compile-time dependency between the two subsystems. The new BACKLIGHT_POWER_ constants have the same values as their FB_BLANK_ counterparts. Hence UAPI and internal semantics do not change. The backlight drivers can be converted one by one. Each instance of FB_BLANK_UNBLANK becomes BACKLIGHT_POWER_ON, each of FB_BLANK_POWERDOWN becomes BACKLIGHT_POWER_OFF, and FB_BLANK_NORMAL becomes BACKLIGHT_POWER_REDUCED. Backlight code or drivers do not use FB_BLANK_VSYNC_SUSPEND and FB_BLANK_HSYNC_SUSPEND, so no new constants for these are being added. The semantics of FB_BLANK_NORMAL appear inconsistent. In fbdev, NORMAL means display off with sync enabled. In backlight code, this translates to turn the backlight off, but some drivers interpret it as backlight on. So we keep the current code as is, but mark BACKLIGHT_POWER_REDUCED as deprecated. Drivers should be fixed and the constant removed. This affects ams369fg06 and a few DRM panel drivers. v2: - rename BL_CORE_ power constants to BACKLIGHT_POWER_ (Sam) - fix documentation Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de> Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org> Link: https://lore.kernel.org/r/20240624152033.25016-2-tzimmermann@suse.de Signed-off-by: Lee Jones <lee@kernel.org>
59 lines
1.9 KiB
Plaintext
59 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 compatible with
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FB_BLANK_* from fb.h
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- 0 (FB_BLANK_UNBLANK) : power on.
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- 4 (FB_BLANK_POWERDOWN) : 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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