Re: [PATCH v3 04/11] backlight: Implement fbdev tracking with blank state from event

[Daniel Thompson <danielt@kernel.org>]

On Thu, Mar 06, 2025 at 03:05:46PM +0100, Thomas Zimmermann wrote:
> Look at the blank state provided by FB_EVENT_BLANK to determine
> whether to enable or disable a backlight. Remove the tracking fields
> from struct backlight_device.
>
> Tracking requires three variables, fb_on, prev_fb_on and the
> backlight's use_count. If fb_on is true, the display has been
> unblanked. The backlight needs to be enabled if the display was
> blanked before (i.e., prev_fb_on is false) or if use_count is still
> at 0. If fb_on is false, the display has been blanked. In this case,
> the backlight has to be disabled was unblanked before and the
> backlight's use_count is greater than 0.
>
> This change removes fbdev state tracking from blacklight. All the
> backlight requires it its own use counter and information about
> changes to the display. Removing fbdev internals makes  backlight
> drivers easier to integrate into other display drivers, such as DRM.
>
> Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>

Reviewed-by: Daniel Thompson (RISCstar) <danielt@kernel.org>


Daniel.