Re: [PATCH v6 01/10] Revert "backlight: Remove notifier"

[Thomas Zimmermann <tzimmermann@suse.de>]

Hi

Am 24.06.26 um 18:57 schrieb Mario Limonciello:
> From: "Mario Limonciello (AMD)" <superm1@kernel.org>
>
> This reverts commit 5461f3fd74a89757f95f351eb0bc26aafc2a2e91.
> The backlight notifier support is needed in order to add backlight
> control support into DRM connectors.
>
> Signed-off-by: Mario Limonciello (AMD) <superm1@kernel.org>
> Tested-by: Simon Ser <contact@emersion.fr>

I don't like this, but I don't have a better idea for now. Therefore

Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>

until a better idea shows up.

> ---
>   drivers/video/backlight/backlight.c | 42 +++++++++++++++++++++++++++++
>   include/linux/backlight.h           | 20 ++++++++++++++
>   2 files changed, 62 insertions(+)
>
> diff --git a/drivers/video/backlight/backlight.c b/drivers/video/backlight/backlight.c
> index a22d0bbb6e639..ff2c2084c73a4 100644
> --- a/drivers/video/backlight/backlight.c
> +++ b/drivers/video/backlight/backlight.c
> @@ -65,6 +65,7 @@
>   
>   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",
> @@ -415,6 +416,9 @@ 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);
> @@ -484,6 +488,9 @@ 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);
> @@ -507,6 +514,40 @@ 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
> @@ -674,6 +715,7 @@ 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 f29a9ef1052e7..d905173c7f73c 100644
> --- a/include/linux/backlight.h
> +++ b/include/linux/backlight.h
> @@ -64,6 +64,24 @@ 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.
> @@ -388,6 +406,8 @@ 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,

-- 
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstr. 146, 90461 Nürnberg, Germany, www.suse.com
GF: Jochen Jaser, Andrew McDonald, Werner Knoblich, (HRB 36809, AG Nürnberg)