Re: [PATCH 01/10] backlight: Add backlight_device_get_by_name()

[Sam Ravnborg <sam@ravnborg.org>]

Hi Noralf.

On Wed, Apr 29, 2020 at 02:48:21PM +0200, Noralf Trønnes wrote:
> Add a way to lookup a backlight device based on its name.
> Will be used by a USB display gadget getting the name from configfs.
> 
> Cc: Lee Jones <lee.jones@linaro.org>
> Cc: Daniel Thompson <daniel.thompson@linaro.org>
> Cc: Jingoo Han <jingoohan1@gmail.com>
> Signed-off-by: Noralf Trønnes <noralf@tronnes.org>

Simple and well-documented.
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
> ---
>  drivers/video/backlight/backlight.c | 21 +++++++++++++++++++++
>  include/linux/backlight.h           |  1 +
>  2 files changed, 22 insertions(+)
> 
> diff --git a/drivers/video/backlight/backlight.c b/drivers/video/backlight/backlight.c
> index cac3e35d7630..92d80aa0c0ef 100644
> --- a/drivers/video/backlight/backlight.c
> +++ b/drivers/video/backlight/backlight.c
> @@ -432,6 +432,27 @@ struct backlight_device *backlight_device_get_by_type(enum backlight_type type)
>  }
>  EXPORT_SYMBOL(backlight_device_get_by_type);
>  
> +/**
> + * backlight_device_get_by_name - Get backlight device by name
> + * @name: Device name
> + *
> + * This function looks up a backlight device by its name. It obtains a reference
> + * on the backlight device and it is the caller's responsibility to drop the
> + * reference by calling backlight_put().
> + *
> + * Returns:
> + * A pointer to the backlight device if found, otherwise NULL.
> + */
> +struct backlight_device *backlight_device_get_by_name(const char *name)
> +{
> +	struct device *dev;
> +
> +	dev = class_find_device_by_name(backlight_class, name);
> +
> +	return dev ? to_backlight_device(dev) : NULL;
> +}
> +EXPORT_SYMBOL(backlight_device_get_by_name);
> +
>  /**
>   * backlight_device_unregister - unregisters a backlight device object.
>   * @bd: the backlight device object to be unregistered and freed.
> diff --git a/include/linux/backlight.h b/include/linux/backlight.h
> index c7d6b2e8c3b5..56e4580d4f55 100644
> --- a/include/linux/backlight.h
> +++ b/include/linux/backlight.h
> @@ -190,6 +190,7 @@ extern void backlight_force_update(struct backlight_device *bd,
>  extern int backlight_register_notifier(struct notifier_block *nb);
>  extern int backlight_unregister_notifier(struct notifier_block *nb);
>  extern struct backlight_device *backlight_device_get_by_type(enum backlight_type type);
> +struct backlight_device *backlight_device_get_by_name(const char *name);
>  extern int backlight_device_set_brightness(struct backlight_device *bd, unsigned long brightness);
>  
>  #define to_backlight_device(obj) container_of(obj, struct backlight_device, dev)
> -- 
> 2.23.0
> 
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