linux-kernel - Re: [PATCH] ARM: samsung: improve static dma

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Date:	Wed, 18 May 2016 17:01:22 +0200
From:	Krzysztof Kozlowski <k.kozlowski@...sung.com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Kukjin Kim <kgene@...nel.org>, Mark Brown <broonie@...nel.org>,
	linux-arm-kernel@...ts.infradead.org,
	linux-samsung-soc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ARM: samsung: improve static dma_mask definition

On 05/12/2016 10:38 AM, Arnd Bergmann wrote:
> When no DMA master devices are part of the kernel configuration,
> we get a warning about the unused dma mask definition:
> 
> arch/arm/plat-samsung/devs.c:71:12: error: 'samsung_device_dma_mask' defined but not used [-Werror=unused-variable]
>  static u64 samsung_device_dma_mask = DMA_BIT_MASK(32);
> 
> We could simply mark this as __maybe_unused to shut up that warning,
> but a nicer solution seems to be to have a separate mask for each
> device. The advantage is that a driver that happens to call
> dma_set_mask() on one device doesn't implicitly change the mask
> for the other devices as well. This is more of a theoretical
> problem, as obviously nothing does it for the devices in this
> file (or they would have always been broken), but it feels
> cleaner that way.
> 
> The definition works by creating an array in place so we can take
> the address of it and let the compiler generate a hidden symbol
> for it at compile time.
> 
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>  arch/arm/plat-samsung/devs.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Thanks, although does not look as critical fix but less warnings makes
spotting right issues faster so applied for v4.7.

Best regards,
Krzysztof