Re: [PATCH v3 06/11] backlight: Replace fb events with a dedicated function call

[Thomas Zimmermann <tzimmermann@suse.de>]

Hi

Am 18.03.25 um 10:23 schrieb Daniel Thompson:
> On Thu, Mar 06, 2025 at 03:05:48PM +0100, Thomas Zimmermann wrote:
>> Remove support for fb events from backlight subsystem. Provide the
>> helper backlight_notify_blank_all() instead. Also export the existing
>> helper backlight_notify_blank() to update a single backlight device.
>>
>> In fbdev, call either helper to inform the backlight subsystem of
>> changes to a display's blank state. If the framebuffer device has a
>> specific backlight, only update this one; otherwise update all.
>>
>> v3:
>> - declare empty fb_bl_notify_blank() as static inline (kernel test robot)
> Looks like there are still configs where we get build failure.
>
>
>> Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
> Other than the build issues, generally this looks great. Just a couple
> of small issues below.
>
>
>> diff --git a/drivers/video/backlight/backlight.c b/drivers/video/backlight/backlight.c
>> index 1c43f579396f..9dc93c5e480b 100644
>> --- a/drivers/video/backlight/backlight.c
>> +++ b/drivers/video/backlight/backlight.c
>> @@ -78,11 +77,8 @@ static const char *const backlight_scale_types[] = {
>>   	[BACKLIGHT_SCALE_NON_LINEAR]	= "non-linear",
>>   };
>>
>> -#if defined(CONFIG_FB_CORE) || (defined(CONFIG_FB_CORE_MODULE) && \
>> -				defined(CONFIG_BACKLIGHT_CLASS_DEVICE_MODULE))
>> -static void backlight_notify_blank(struct backlight_device *bd,
>> -				   struct device *display_dev,
>> -				   bool fb_on, bool prev_fb_on)
>> +void backlight_notify_blank(struct backlight_device *bd, struct device *display_dev,
>> +			    bool fb_on, bool prev_fb_on)
>>   {
>>   	guard(mutex)(&bd->ops_lock);
>>
>> @@ -103,68 +99,18 @@ static void backlight_notify_blank(struct backlight_device *bd,
>>   		}
>>   	}
>>   }
>> +EXPORT_SYMBOL(backlight_notify_blank);
> Should this be EXPORT_SYMBOL_GPL()?

The other symbols in this source file are exported with EXPORT_SYMBOL().

Best regards
Thomas

>
>
>> -/*
>> - * fb_notifier_callback
>> - *
>> - * This callback gets called when something important happens inside a
>> - * framebuffer driver. The backlight core only cares about FB_BLANK_UNBLANK
>> - * which is reported to the driver using backlight_update_status()
>> - * as a state change.
>> - *
>> - * There may be several fbdev's connected to the backlight device,
>> - * in which case they are kept track of. A state change is only reported
>> - * if there is a change in backlight for the specified fbdev.
>> - */
>> -static int fb_notifier_callback(struct notifier_block *self,
>> -				unsigned long event, void *data)
>> +void backlight_notify_blank_all(struct device *display_dev, bool fb_on, bool prev_fb_on)
>>   {
>>   	struct backlight_device *bd;
>> -	struct fb_event *evdata = data;
>> -	struct fb_info *info = evdata->info;
>> -	const int *fb_blank = evdata->data;
>> -	struct backlight_device *fb_bd = fb_bl_device(info);
>> -	bool fb_on, prev_fb_on;
>> -
>> -	/* If we aren't interested in this event, skip it immediately ... */
>> -	if (event != FB_EVENT_BLANK)
>> -		return 0;
>> -
>> -	bd = container_of(self, struct backlight_device, fb_notif);
>> -
>> -	if (fb_bd && fb_bd != bd)
>> -		return 0;
>> -
>> -	fb_on = fb_blank[0] == FB_BLANK_UNBLANK;
>> -	prev_fb_on = fb_blank[1] == FB_BLANK_UNBLANK;
>> -
>> -	backlight_notify_blank(bd, info->device, fb_on, prev_fb_on);
>> -
>> -	return 0;
>> -}
>> -
>> -static int backlight_register_fb(struct backlight_device *bd)
>> -{
>> -	memset(&bd->fb_notif, 0, sizeof(bd->fb_notif));
>> -	bd->fb_notif.notifier_call = fb_notifier_callback;
>>
>> -	return fb_register_client(&bd->fb_notif);
>> -}
>> +	guard(mutex)(&backlight_dev_list_mutex);
>>
>> -static void backlight_unregister_fb(struct backlight_device *bd)
>> -{
>> -	fb_unregister_client(&bd->fb_notif);
>> -}
>> -#else
>> -static inline int backlight_register_fb(struct backlight_device *bd)
>> -{
>> -	return 0;
>> +	list_for_each_entry(bd, &backlight_dev_list, entry)
>> +		backlight_notify_blank(bd, display_dev, fb_on, prev_fb_on);
>>   }
>> -
>> -static inline void backlight_unregister_fb(struct backlight_device *bd)
>> -{
>> -}
>> -#endif /* CONFIG_FB_CORE */
>> +EXPORT_SYMBOL(backlight_notify_blank_all);
> Same here.
>
>
> Daniel.

-- 
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)