The module pointer in class_create() never actually did anything, and it
shouldn't have been requred to be set as a parameter even if it did
something.  So just remove it and fix up all callers of the function in
the kernel tree at the same time.

Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Acked-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Link: https://lore.kernel.org/r/20230313181843.1207845-4-gregkh@linuxfoundation.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

backlight_put() has been dropped, we should call put_device() to drop
the reference taken by backlight_device_get_by_name().

Fixes: 0f6a3256fd81 ("backlight: backlight: Drop backlight_put()")
Signed-off-by: Miaoqian Lin <linmq006@gmail.com>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Lee Jones <lee@kernel.org>
Link: https://lore.kernel.org/r/20221215071902.424005-1-linmq006@gmail.com

Use devm_add_action_or_reset() instead of devm_add_action()+hand writing
what is done in the release function, should an error occur.

This is more straightforward and saves a few lines of code.

While at it, remove a useless test in devm_backlight_release(). 'data' is
known to be not NULL when this function is called.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/f998a4291d865273afa0d1f85764a9ac7fbc1b64.1644738084.git.christophe.jaillet@wanadoo.fr

backlight.h documents "struct backlight_ops->get_brightness()" to return
a negative errno on failure.

So far these errors have not been handled in the backlight core.
This leads to negative values being exposed through sysfs although only
positive values are documented to be reported.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

The note in c2adda27d202f ("video: backlight: Add of_find_backlight helper
in backlight.c") says that gpio-backlight uses brightness as power state.
This has been fixed since in ec665b756e6f7 ("backlight: gpio-backlight:
Correct initial power state handling") and other backlight drivers do not
require this workaround. Drop the workaround.

This fixes the case where e.g. pwm-backlight can perfectly well be set to
brightness 0 on boot in DT, which without this patch leads to the display
brightness to be max instead of off.

Fixes: c2adda27d202f ("video: backlight: Add of_find_backlight helper in backlight.c")
Cc: <stable@vger.kernel.org> # 5.4+
Cc: <stable@vger.kernel.org> # 4.19.x: ec665b756e6f7: backlight: gpio-backlight: Correct initial power state handling
Signed-off-by: Marek Vasut <marex@denx.de>
Acked-by: Noralf Trønnes <noralf@tronnes.org>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

There are no external users of of_find_backlight, as they have all
changed to use the managed version. Make of_find_backlight static to
prevent new external users.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

There are no external users of backlight_put(). Drop it and open code
the two users in backlight.c.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

Add overview chapter to backlight.c.

Update existing kernel-doc to follow a more consistent style and drop
kernel-doc for deprecated functions.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

Increase readability of fb_notifier_callback() by removing
a few indent levels.

No functional change.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

Kerneldoc syntax is used, but not complete.  Descriptions required.

Prevents warnings like:

 drivers/video/backlight/backlight.c:329: warning: Function parameter or member 'reason' not described in 'backlight_force_update'
 drivers/video/backlight/backlight.c:354: warning: Function parameter or member 'props' not described in 'backlight_device_register'

Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
Cc: Jamey Hicks <jamey.hicks@hp.com>
Cc: Andrew Zabolotny <zap@homelink.ru>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>