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

[Lee Jones]

On Wed, 29 Apr 2020, 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 at linaro.org>
> Cc: Daniel Thompson <daniel.thompson at linaro.org>
> Cc: Jingoo Han <jingoohan1 at gmail.com>
> Signed-off-by: Noralf Trønnes <noralf at tronnes.org>
> ---
>  drivers/video/backlight/backlight.c | 21 +++++++++++++++++++++
>  include/linux/backlight.h           |  1 +
>  2 files changed, 22 insertions(+)

Once reviewed, can this patch be applied on its own?

My guess is that it can't, as the other patches in this set depend on
it, right?  If this assumption is true, you need to send me the rest
of the set.

FYI: It's normally better to send the whole set to everyone, as it
provides visibility on current review (or lack there of) status of the
other patches and allows each of the maintainers to discuss possible
merge strategies.

> 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)

-- 
Lee Jones [李琼斯]
Linaro Services Technical Lead
Linaro.org │ Open source software for ARM SoCs
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