linux-kernel - Re: [PATCH] dmaengine: edma: fix build without CONFIG

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Date:	Wed, 04 Nov 2015 09:46:41 +0100
From:	Arnd Bergmann <arnd@...db.de>
To:	Peter Ujfalusi <peter.ujfalusi@...com>
Cc:	Vinod Koul <vinod.koul@...el.com>, dmaengine@...r.kernel.org,
	Dan Williams <dan.j.williams@...el.com>,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	Sekhar Nori <nsekhar@...com>,
	Kevin Hilman <khilman@...prootsystems.com>,
	linux-omap@...r.kernel.org
Subject: Re: [PATCH] dmaengine: edma: fix build without CONFIG_OF

On Wednesday 04 November 2015 09:42:35 Peter Ujfalusi wrote:
> On 11/03/2015 04:00 PM, Arnd Bergmann wrote:
> > During the edma rework, a build error was introduced for the
> > case that CONFIG_OF is disabled:
> > 
> > drivers/built-in.o: In function `edma_tc_set_pm_state':
> > :(.text+0x43bf0): undefined reference to `of_find_device_by_node'
> > 
> > As the edma_tc_set_pm_state() function does nothing in case
> > we are running without OF, this adds an IS_ENABLED() check
> > that turns the function into an empty stub then and avoids the
> > link error.
> > 
> > Signed-off-by: Arnd Bergmann <arnd@...db.de>
> > Fixes: ca304fa9bb76 ("ARM/dmaengine: edma: Public API to use private struct pointer")
> 
> The actual commit this patch is fixing is:
> 1be5336bc7ba dmaengine: edma: New device tree binding

That's what I first thought, but it seems to just move around the
call to of_find_device_by_node that was first introduced in the
commit I mentioned. Did you build-test it successfully with
ca304fa9bb76 and CONFIG_OF enabled? I have to admit that I
was just guessing from the contents and did not bisect this
fully.

> > ---
> > Found on ARM randconfig builds with today's linux-next
> 
> I have sanity built the kernel with omap2plus_defconfig and
> davinci_all_defconfig since eDMA is used by these platforms and did not faced
> with this issue, as obviously these defconfigs will result OF to be enabled.

Right. The defconfigs were all fine, and this is hard to hit
even in the randconfig builds.

> > diff --git a/drivers/dma/edma.c b/drivers/dma/edma.c
> > index 31722d436a42..16713a93da10 100644
> > --- a/drivers/dma/edma.c
> > +++ b/drivers/dma/edma.c
> > @@ -1560,7 +1560,7 @@ static void edma_tc_set_pm_state(struct edma_tc *tc, bool enable)
> >       struct platform_device *tc_pdev;
> >       int ret;
> >  
> > -     if (!tc)
> > +     if (!IS_ENABLED(CONFIG_OF) || !tc)
> >               return;
> 
> Should we instead put the function inside of:
> #if IS_ENABLED(CONFIG_OF)
> static void edma_tc_set_pm_state(struct edma_tc *tc, bool enable)
> {
> ...
> }
> #else
> static inline void edma_tc_set_pm_state(struct edma_tc *tc, bool enable)
> {
> }
> #endif /* IS_ENABLED(CONFIG_OF) */

I think that would be less readable, and gives no compile-time coverage
to the contents of the edma_tc_set_pm_state function.

The effect is the same, so I'd rather stay with my version.

	Arnd
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