# \[PATCH\] video: backlight: Drop maximum brightness override for brightness zero - Subsystems: FRAMEBUFFER LAYER, BACKLIGHT CLASS/SUBSYSTEM, THE REST - Maintainers: Helge Deller, Lee Jones, Daniel Thompson, Jingoo Han, Linus Torvalds - List: linux-fbdev - 3 messages, 3 authors - Page: https://ratatoskr.run/linux-fbdev/2021/07/9202993/t ## \[PATCH\] video: backlight: Drop maximum brightness override for brightness zero - From: Marek Vasut \ - Date: 2021-07-09 13:26:26 - Message: https://ratatoskr.run/linux-fbdev/2021/07/9202993.md ```text 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") Signed-off-by: Marek Vasut Cc: Daniel Thompson Cc: Meghana Madhyastha Cc: Noralf Trønnes Cc: Sean Paul Cc: Thierry Reding --- drivers/video/backlight/backlight.c | 6 ------ 1 file changed, 6 deletions(-) diff --git a/drivers/video/backlight/backlight.c b/drivers/video/backlight/backlight.c index 537fe1b376ad7..fc990e576340b 100644 --- a/drivers/video/backlight/backlight.c +++ b/drivers/video/backlight/backlight.c @@ -688,12 +688,6 @@ static struct backlight_device *of_find_backlight(struct device *dev) of_node_put(np); if (!bd) return ERR_PTR(-EPROBE_DEFER); - /* - * Note: gpio_backlight uses brightness as - * power state during probe - */ - if (!bd->props.brightness) - bd->props.brightness = bd->props.max_brightness; } } -- 2.30.2 ``` ## Re: \[PATCH\] video: backlight: Drop maximum brightness override for brightness zero - From: Noralf Trønnes \ - Date: 2021-07-09 13:53:22 - Message: https://ratatoskr.run/linux-fbdev/2021/07/9202994.md ```text Den 09.07.2021 15.26, skrev Marek Vasut: > 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") I not sure about the rules, but if this is automatically picked up for stable, maybe this is needed to avoid changing behaviour on 4.19: Cc: # 5.4+ of_find_backlight() was added in 4.17 and the gpio fix in 5.4. Or perhaps there are other ways to signal this dependency. > Signed-off-by: Marek Vasut > Cc: Daniel Thompson > Cc: Meghana Madhyastha > Cc: Noralf Trønnes > Cc: Sean Paul > Cc: Thierry Reding > --- Acked-by: Noralf Trønnes ``` ## Re: \[PATCH\] video: backlight: Drop maximum brightness override for brightness zero - From: Daniel Thompson \ - Date: 2021-07-12 10:25:59 - Message: https://ratatoskr.run/linux-fbdev/2021/07/9203115.md ```text On Fri, Jul 09, 2021 at 03:53:16PM +0200, Noralf Trønnes wrote: > > > Den 09.07.2021 15.26, skrev Marek Vasut: > > 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") > > I not sure about the rules, but if this is automatically picked up for > stable, maybe this is needed to avoid changing behaviour on 4.19: > > > of_find_backlight() was added in 4.17 and the gpio fix in 5.4. > > Or perhaps there are other ways to signal this dependency. Agree we need to make sure the Fixes: tag doesn't provoke regressions in v4.19. Is this the syntax appropriate? Cc: # 5.4+ Cc: # 4.19.x: ec665b756e6f7: backlight: gpio-backlight: Correct initial power state handling > > Signed-off-by: Marek Vasut > > Cc: Daniel Thompson > > Cc: Meghana Madhyastha > > Cc: Noralf Trønnes > > Cc: Sean Paul > > Cc: Thierry Reding > > --- > > Acked-by: Noralf Trønnes With the above (or something similar to avoid problems with v4.19): Reviewed-by: Daniel Thompson Daniel. ```