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2025-05-05docs: backlight: Clarify `actual_brightness`Mario Limonciello
Currently userspace software systemd treats `brightness` and `actual_brightness` identically due to a bug found in an out of tree driver. This however causes problems for in-tree drivers that use brightness to report user requested `brightness` and `actual_brightness` to report what the hardware actually has programmed. Clarify the documentation to match the behavior described in commit 6ca017658b1f9 ("[PATCH] backlight: Backlight Class Improvements"). Cc: Lee Jones <lee@kernel.org> Cc: Lennart Poettering <lennart@poettering.net> Cc: richard.purdie@linuxfoundation.org Link: https://github.com/systemd/systemd/pull/36881 Reviewed-by: Harry Wentland <harry.wentland@amd.com> Link: https://lore.kernel.org/r/20250415192101.2033518-1-superm1@kernel.org Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
2024-07-04backlight: Add BACKLIGHT_POWER_ constants for power statesThomas Zimmermann
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>
2020-10-30docs: ABI: stable: make files ReST compatibleMauro Carvalho Chehab
Several entries at the stable ABI files won't parse if we pass them directly to the ReST output. Adjust them, in order to allow adding their contents as-is at the stable ABI book. Acked-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org> Acked-by: Jonathan Corbet <corbet@lwn.net> Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org> Link: https://lore.kernel.org/r/467a0dfbcdf00db710a629d3fe4a2563750339d8.1604042072.git.mchehab+huawei@kernel.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2011-03-22backlight: add backlight typeMatthew Garrett
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>
2009-08-28video/backlight: document sysfs interfaceCorentin Chary
Date and KernelVersion may be wrong because the backlight interface was introduced before git initial import. Cc:Richard Purdie <rpurdie@rpsys.net> Signed-off-by: Corentin Chary <corentincj@iksaif.net> Signed-off-by: Len Brown <len.brown@intel.com>