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

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Message-ID: <1767565.D903P0xsEy@diego>
Date:	Tue, 11 Nov 2014 00:41:10 +0100
From:	Heiko Stübner <heiko@...ech.de>
To:	Lee Jones <lee.jones@...aro.org>
Cc:	Jingoo Han <jg1.han@...sung.com>, 'Bryan Wu' <cooloney@...il.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] backlight: use of_find_backlight_by_node stub when backlight class disabled

Hi,

Am Dienstag, 4. November 2014, 17:15:32 schrieb Lee Jones:
> Actually there is a better way still:
> 
> #ifdef CONFIG_OF && IS_ENABLED(CONFIG_BACKLIGHT_CLASS_DEVICE)
> 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

After further looking at the problem, I'm actually not even sure, if my 
approach is the best one at all.

The problem I was trying to fix was panel-simple (drivers/gpu/drm/panel/panel-
simple.c) checking for an optional backlight, while not depending on the 
backlight-class itself.

As both components do not have a relationship, there exist the possibility of 
panel-simply being build into the kernel while the backlight_class is build as 
module. So while the IS_ENABLED check would define the prototype, panel-generic 
would still miss the function when linking.

Should panel-generic simply depend in the backlight_class instead?

Thanks
Heiko
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