Re: [PATCH 12/13] leds: backlight trigger: Replace fb events with a dedicated function call

[Lee Jones <lee@kernel.org>]

On Thu, 06 Feb 2025, Thomas Zimmermann wrote:

> Remove support for fb events from the led backlight trigger. Provide the
> helper ledtrig_backlight_blank() instead. Call it from fbdev to inform
> the trigger of changes to a display's blank state.
> 
> Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
> ---
>  drivers/leds/trigger/ledtrig-backlight.c | 31 +++++-------------------
>  drivers/video/fbdev/core/fbmem.c         | 21 +++++++++-------
>  include/linux/leds.h                     |  6 +++++
>  3 files changed, 24 insertions(+), 34 deletions(-)
> 
> diff --git a/drivers/leds/trigger/ledtrig-backlight.c b/drivers/leds/trigger/ledtrig-backlight.c
> index f9317f93483b..e3ae4adc29e3 100644
> --- a/drivers/leds/trigger/ledtrig-backlight.c
> +++ b/drivers/leds/trigger/ledtrig-backlight.c
> @@ -10,7 +10,6 @@
>  #include <linux/kernel.h>
>  #include <linux/slab.h>
>  #include <linux/init.h>
> -#include <linux/fb.h>
>  #include <linux/leds.h>
>  #include "../leds.h"
>  
> @@ -21,7 +20,6 @@ struct bl_trig_notifier {
>  	struct led_classdev *led;
>  	int brightness;
>  	int old_status;
> -	struct notifier_block notifier;
>  	unsigned invert;
>  
>  	struct list_head entry;
> @@ -30,7 +28,7 @@ struct bl_trig_notifier {
>  static struct list_head ledtrig_backlight_list;
>  static struct mutex ledtrig_backlight_list_mutex;
>  
> -static void ledtrig_backlight_blank(struct bl_trig_notifier *n, bool on)
> +static void __ledtrig_backlight_blank(struct bl_trig_notifier *n, bool on)

I'm confused.  Didn't you just introduce this?

>  {
>  	struct led_classdev *led = n->led;
>  	int new_status = !on ? BLANK : UNBLANK;
> @@ -48,23 +46,14 @@ static void ledtrig_backlight_blank(struct bl_trig_notifier *n, bool on)
>  	n->old_status = new_status;
>  }
>  
> -static int fb_notifier_callback(struct notifier_block *p,
> -				unsigned long event, void *data)
> +void ledtrig_backlight_blank(bool on)
>  {
> -	struct bl_trig_notifier *n = container_of(p,
> -					struct bl_trig_notifier, notifier);
> -	struct fb_event *fb_event = data;
> -	int *blank;
> -
> -	/* If we aren't interested in this event, skip it immediately ... */
> -	if (event != FB_EVENT_BLANK)
> -		return 0;
> -
> -	blank = fb_event->data;
> +	struct bl_trig_notifier *n;
>  
> -	ledtrig_backlight_blank(n, !blank[0]);
> +	guard(mutex)(&ledtrig_backlight_list_mutex);
>  
> -	return 0;
> +	list_for_each_entry(n, &ledtrig_backlight_list, entry)
> +		__ledtrig_backlight_blank(n, on);
>  }
>  
>  static ssize_t bl_trig_invert_show(struct device *dev,
> @@ -110,8 +99,6 @@ ATTRIBUTE_GROUPS(bl_trig);
>  
>  static int bl_trig_activate(struct led_classdev *led)
>  {
> -	int ret;
> -
>  	struct bl_trig_notifier *n;
>  
>  	n = kzalloc(sizeof(struct bl_trig_notifier), GFP_KERNEL);
> @@ -122,11 +109,6 @@ static int bl_trig_activate(struct led_classdev *led)
>  	n->led = led;
>  	n->brightness = led->brightness;
>  	n->old_status = UNBLANK;
> -	n->notifier.notifier_call = fb_notifier_callback;
> -
> -	ret = fb_register_client(&n->notifier);
> -	if (ret)
> -		dev_err(led->dev, "unable to register backlight trigger\n");
>  
>  	mutex_lock(&ledtrig_backlight_list_mutex);
>  	list_add(&n->entry, &ledtrig_backlight_list);
> @@ -143,7 +125,6 @@ static void bl_trig_deactivate(struct led_classdev *led)
>  	list_del(&n->entry);
>  	mutex_unlock(&ledtrig_backlight_list_mutex);
>  
> -	fb_unregister_client(&n->notifier);
>  	kfree(n);
>  }
>  
> diff --git a/drivers/video/fbdev/core/fbmem.c b/drivers/video/fbdev/core/fbmem.c
> index fb7ca143a996..92c3fe2a7aff 100644
> --- a/drivers/video/fbdev/core/fbmem.c
> +++ b/drivers/video/fbdev/core/fbmem.c
> @@ -16,6 +16,7 @@
>  #include <linux/fb.h>
>  #include <linux/fbcon.h>
>  #include <linux/lcd.h>
> +#include <linux/leds.h>
>  
>  #include <video/nomodeset.h>
>  
> @@ -373,11 +374,19 @@ static void fb_lcd_notify_blank(struct fb_info *info)
>  #endif
>  }
>  
> +static void fb_ledtrig_backlight_notify_blank(struct fb_info *info)
> +{
> +#if IS_REACHABLE(CONFIG_LEDS_TRIGGER_BACKLIGHT)

#iferry is generally discouraged in C files.

Does is_defined() work for you?
/
> +	if (info->blank == FB_BLANK_UNBLANK)
> +		ledtrig_backlight_blank(true);

If !CONFIG_LEDS_TRIGGER_BACKLIGHT(), then ledtrig_backlight_blank() is a
noop anyway, right?  So why encompass it in the #if at all?

> +	else
> +		ledtrig_backlight_blank(false);
> +#endif
> +}
> +
>  int fb_blank(struct fb_info *info, int blank)
>  {
>  	int old_blank = info->blank;
> -	struct fb_event event;
> -	int data[2];
>  	int ret;
>  
>  	if (!info->fbops->fb_blank)
> @@ -386,11 +395,6 @@ int fb_blank(struct fb_info *info, int blank)
>  	if (blank > FB_BLANK_POWERDOWN)
>  		blank = FB_BLANK_POWERDOWN;
>  
> -	data[0] = blank;
> -	data[1] = old_blank;
> -	event.info = info;
> -	event.data = data;
> -
>  	info->blank = blank;
>  
>  	ret = info->fbops->fb_blank(blank, info);
> @@ -399,8 +403,7 @@ int fb_blank(struct fb_info *info, int blank)
>  
>  	fb_bl_notify_blank(info, old_blank);
>  	fb_lcd_notify_blank(info);
> -
> -	fb_notifier_call_chain(FB_EVENT_BLANK, &event);
> +	fb_ledtrig_backlight_notify_blank(info);
>  
>  	return 0;
>  
> diff --git a/include/linux/leds.h b/include/linux/leds.h
> index 98f9719c924c..8c7c41888f7d 100644
> --- a/include/linux/leds.h
> +++ b/include/linux/leds.h
> @@ -640,6 +640,12 @@ static inline void ledtrig_flash_ctrl(bool on) {}
>  static inline void ledtrig_torch_ctrl(bool on) {}
>  #endif
>  
> +#if IS_ENABLED(CONFIG_LEDS_TRIGGER_BACKLIGHT)
> +void ledtrig_backlight_blank(bool on);
> +#else
> +static inline void ledtrig_backlight_blank(bool on) {}
> +#endif
> +
>  /*
>   * Generic LED platform data for describing LED names and default triggers.
>   */
> -- 
> 2.48.1
> 

-- 
/fb_ledtrig_backlight_notify_blankLee Jones [李琼斯]