linux-kernel - Re: [PATCH] fbdev: auo_k190x: avoid unused function warnings

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Message-ID: <1678174.Yl1Wo71dkn@wuerfel>
Date:	Mon, 07 Dec 2015 17:16:43 +0100
From:	Arnd Bergmann <arnd@...db.de>
To:	Tomi Valkeinen <tomi.valkeinen@...com>
Cc:	Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
	linux-fbdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] fbdev: auo_k190x: avoid unused function warnings

On Monday 07 December 2015 18:10:04 Tomi Valkeinen wrote:
> On 20/11/15 23:47, Arnd Bergmann wrote:
> > The auo_k190x framebuffer driver encloses the power-management
> > functions in #ifdef CONFIG_PM, but the auok190x_suspend/resume
> > functions are only really used when CONFIG_PM_SLEEP is also
> > set, as a frequent gcc warning shows:
> > 
> > drivers/video/fbdev/auo_k190x.c:859:12: warning: 'auok190x_suspend' defined but not used
> > drivers/video/fbdev/auo_k190x.c:899:12: warning: 'auok190x_resume' defined but not used
> > 
> > This changes the driver to remove the #ifdef and instead mark
> > the functions as __maybe_unused, which is a nicer anyway, as it
> > provides build testing for all the code in all configurations
> > and is harder to get wrong.
> 
> Applied for 4.5.
> 
> Btw, do you know if the linker will optimize the __maybe_unused funcs
> away if they are not used? I presume so.
> 

The compiler does it correctly when built with -O1 or higher (we don't
support -O0), and the linker is not involved here.

	Arnd
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