backlight: Remove notifier

From: "Dr. David Alan Gilbert" <linux@treblig.org>

backlight_register_notifier and backlight_unregister_notifier have
been unused since
  commit 6cb634d0dc85 ("ACPI: video: Remove code to unregister acpi_video
backlight when a native backlight registers")

With those not being called, it means that the backlight_notifier
list is always empty.

Remove the functions, the list itself and the enum used in the
notifications.

Signed-off-by: Dr. David Alan Gilbert <linux@treblig.org>
---
 drivers/video/backlight/backlight.c | 42 -----------------------------
 include/linux/backlight.h           | 20 --------------
 2 files changed, 62 deletions(-)

On Fri, Sep 20, 2024 at 12:27:58AM +0100, linux@treblig.org wrote:
> From: "Dr. David Alan Gilbert" <linux@treblig.org>
> 
> backlight_register_notifier and backlight_unregister_notifier have
> been unused since
>   commit 6cb634d0dc85 ("ACPI: video: Remove code to unregister acpi_video
> backlight when a native backlight registers")
> 
> With those not being called, it means that the backlight_notifier
> list is always empty.
> 
> Remove the functions, the list itself and the enum used in the
> notifications.
> 
> Signed-off-by: Dr. David Alan Gilbert <linux@treblig.org>

Reviewed-by: Simona Vetter <simona.vetter@ffwll.ch>

I think Lee Jones or Daniel Thompson will pick this up.
-Sima

> ---
>  drivers/video/backlight/backlight.c | 42 -----------------------------
>  include/linux/backlight.h           | 20 --------------
>  2 files changed, 62 deletions(-)
> 
> diff --git a/drivers/video/backlight/backlight.c b/drivers/video/backlight/backlight.c
> index a82934694d05..f699e5827ccb 100644
> --- a/drivers/video/backlight/backlight.c
> +++ b/drivers/video/backlight/backlight.c
> @@ -65,7 +65,6 @@
>  
>  static struct list_head backlight_dev_list;
>  static struct mutex backlight_dev_list_mutex;
> -static struct blocking_notifier_head backlight_notifier;
>  
>  static const char *const backlight_types[] = {
>  	[BACKLIGHT_RAW] = "raw",
> @@ -467,9 +466,6 @@ struct backlight_device *backlight_device_register(const char *name,
>  	list_add(&new_bd->entry, &backlight_dev_list);
>  	mutex_unlock(&backlight_dev_list_mutex);
>  
> -	blocking_notifier_call_chain(&backlight_notifier,
> -				     BACKLIGHT_REGISTERED, new_bd);
> -
>  	return new_bd;
>  }
>  EXPORT_SYMBOL(backlight_device_register);
> @@ -539,9 +535,6 @@ void backlight_device_unregister(struct backlight_device *bd)
>  	mutex_unlock(&pmac_backlight_mutex);
>  #endif
>  
> -	blocking_notifier_call_chain(&backlight_notifier,
> -				     BACKLIGHT_UNREGISTERED, bd);
> -
>  	mutex_lock(&bd->ops_lock);
>  	bd->ops = NULL;
>  	mutex_unlock(&bd->ops_lock);
> @@ -566,40 +559,6 @@ static int devm_backlight_device_match(struct device *dev, void *res,
>  	return *r == data;
>  }
>  
> -/**
> - * backlight_register_notifier - get notified of backlight (un)registration
> - * @nb: notifier block with the notifier to call on backlight (un)registration
> - *
> - * Register a notifier to get notified when backlight devices get registered
> - * or unregistered.
> - *
> - * RETURNS:
> - *
> - * 0 on success, otherwise a negative error code
> - */
> -int backlight_register_notifier(struct notifier_block *nb)
> -{
> -	return blocking_notifier_chain_register(&backlight_notifier, nb);
> -}
> -EXPORT_SYMBOL(backlight_register_notifier);
> -
> -/**
> - * backlight_unregister_notifier - unregister a backlight notifier
> - * @nb: notifier block to unregister
> - *
> - * Register a notifier to get notified when backlight devices get registered
> - * or unregistered.
> - *
> - * RETURNS:
> - *
> - * 0 on success, otherwise a negative error code
> - */
> -int backlight_unregister_notifier(struct notifier_block *nb)
> -{
> -	return blocking_notifier_chain_unregister(&backlight_notifier, nb);
> -}
> -EXPORT_SYMBOL(backlight_unregister_notifier);
> -
>  /**
>   * devm_backlight_device_register - register a new backlight device
>   * @dev: the device to register
> @@ -767,7 +726,6 @@ static int __init backlight_class_init(void)
>  
>  	INIT_LIST_HEAD(&backlight_dev_list);
>  	mutex_init(&backlight_dev_list_mutex);
> -	BLOCKING_INIT_NOTIFIER_HEAD(&backlight_notifier);
>  
>  	return 0;
>  }
> diff --git a/include/linux/backlight.h b/include/linux/backlight.h
> index ea9c1bc8148e..f5652e5a9060 100644
> --- a/include/linux/backlight.h
> +++ b/include/linux/backlight.h
> @@ -66,24 +66,6 @@ enum backlight_type {
>  	BACKLIGHT_TYPE_MAX,
>  };
>  
> -/**
> - * enum backlight_notification - the type of notification
> - *
> - * The notifications that is used for notification sent to the receiver
> - * that registered notifications using backlight_register_notifier().
> - */
> -enum backlight_notification {
> -	/**
> -	 * @BACKLIGHT_REGISTERED: The backlight device is registered.
> -	 */
> -	BACKLIGHT_REGISTERED,
> -
> -	/**
> -	 * @BACKLIGHT_UNREGISTERED: The backlight revice is unregistered.
> -	 */
> -	BACKLIGHT_UNREGISTERED,
> -};
> -
>  /** enum backlight_scale - the type of scale used for brightness values
>   *
>   * The type of scale used for brightness values.
> @@ -421,8 +403,6 @@ void devm_backlight_device_unregister(struct device *dev,
>  				      struct backlight_device *bd);
>  void backlight_force_update(struct backlight_device *bd,
>  			    enum backlight_update_reason reason);
> -int backlight_register_notifier(struct notifier_block *nb);
> -int backlight_unregister_notifier(struct notifier_block *nb);
>  struct backlight_device *backlight_device_get_by_name(const char *name);
>  struct backlight_device *backlight_device_get_by_type(enum backlight_type type);
>  int backlight_device_set_brightness(struct backlight_device *bd,
> -- 
> 2.46.1
>