linux-kernel - Re: [PATCH] backlight: Add of_find_backlight_by

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Date:	Thu, 15 Nov 2012 10:30:11 +0900
From:	Jingoo Han <jg1.han@...sung.com>
To:	'Thierry Reding' <thierry.reding@...onic-design.de>,
	'Andrew Morton' <akpm@...ux-foundation.org>
Cc:	'Richard Purdie' <rpurdie@...ys.net>,
	'Florian Tobias Schandinat' <FlorianSchandinat@....de>,
	linux-fbdev@...r.kernel.org, devicetree-discuss@...ts.ozlabs.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] backlight: Add of_find_backlight_by_node() function

On Friday, November 09, 2012 11:05 PM Thierry Reding wrote
> 
> This function finds the struct backlight_device for a given device tree
> node. A dummy function is provided so that it safely compiles out if OF
> support is disabled.
> 
> Signed-off-by: Thierry Reding <thierry.reding@...onic-design.de>

CC'ed Andrew Morton

Hi Thierry Reding,

The patch itself looks good.
Could you explain when this API is used?
Thank you.


Best regards,
Jingoo Han

> ---
>  drivers/video/backlight/backlight.c | 17 +++++++++++++++++
>  include/linux/backlight.h           | 10 ++++++++++
>  2 files changed, 27 insertions(+)
> 
> diff --git a/drivers/video/backlight/backlight.c b/drivers/video/backlight/backlight.c
> index 297db2f..0d1ed4f 100644
> --- a/drivers/video/backlight/backlight.c
> +++ b/drivers/video/backlight/backlight.c
> @@ -370,6 +370,23 @@ void backlight_device_unregister(struct backlight_device *bd)
>  }
>  EXPORT_SYMBOL(backlight_device_unregister);
> 
> +#if IS_ENABLED(CONFIG_OF)
> +static int of_parent_match(struct device *dev, void *data)
> +{
> +	return dev->parent && dev->parent->of_node == data;
> +}
> +
> +struct backlight_device *of_find_backlight_by_node(struct device_node *node)
> +{
> +	struct device *dev;
> +
> +	dev = class_find_device(backlight_class, NULL, node, of_parent_match);
> +
> +	return dev ? to_backlight_device(dev) : NULL;
> +}
> +EXPORT_SYMBOL(of_find_backlight_by_node);
> +#endif
> +
>  static void __exit backlight_class_exit(void)
>  {
>  	class_destroy(backlight_class);
> diff --git a/include/linux/backlight.h b/include/linux/backlight.h
> index 5ffc6dd..11840e9 100644
> --- a/include/linux/backlight.h
> +++ b/include/linux/backlight.h
> @@ -134,4 +134,14 @@ struct generic_bl_info {
>  	void (*kick_battery)(void);
>  };
> 
> +#if IS_ENABLED(CONFIG_OF)
> +struct backlight_device *of_find_backlight_by_node(struct device_node *node);
> +#else
> +static inline struct backlight_device *
> +of_find_backlight_by_node(struct device_node *node)
> +{
> +	return NULL;
> +}
> +#endif
> +
>  #endif
> --
> 1.8.0
> 
> --
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