linux-kernel - Re: [PATCH] [media] media: Kconfig: add dependency of HAS

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Message-id: <569660F7.2000802@samsung.com>
Date:	Wed, 13 Jan 2016 15:36:39 +0100
From:	Marek Szyprowski <m.szyprowski@...sung.com>
To:	Sakari Ailus <sakari.ailus@....fi>,
	Sudip Mukherjee <sudipm.mukherjee@...il.com>
Cc:	Mauro Carvalho Chehab <mchehab@....samsung.com>,
	linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>, hverkuil@...all.nl,
	pawel@...iak.com, kyungmin.park@...sung.com
Subject: Re: [PATCH] [media] media: Kconfig: add dependency of HAS_DMA

Hello,

On 2016-01-12 15:10, Sakari Ailus wrote:
> On Mon, Jan 11, 2016 at 06:23:11PM +0530, Sudip Mukherjee wrote:
>> On Wed, Dec 30, 2015 at 06:56:03PM +0530, Sudip Mukherjee wrote:
>>> The build of m32r allmodconfig fails with the error:
>>> drivers/media/v4l2-core/videobuf2-dma-contig.c:484:2:
>>> 	error: implicit declaration of function 'dma_get_cache_alignment'
>>>
>>> The build of videobuf2-dma-contig.c depends on HAS_DMA and it is
>>> correctly mentioned in the Kconfig but the symbol VIDEO_STI_BDISP also
>>> selects VIDEOBUF2_DMA_CONTIG, so it is trying to compile
>>> videobuf2-dma-contig.c even though HAS_DMA is not defined.
>>>
>>> Signed-off-by: Sudip Mukherjee <sudip@...torindia.org>
>>> ---
>> A gentle ping. m32r allmodconfig still fails with next-20160111. Build
>> log is at:
>> https://travis-ci.org/sudipm-mukherjee/parport/jobs/101536379
> Hi Sudip,
>
> Even though the issue now manifests itself on m32r, the problem is wider
> than that: dma_get_cache_alignment() is only defined if CONFIG_HAS_DMA is
> set.
>
> I wonder if using videobuf2-dma-contig makes any sense if HAS_DMA is
> disabled, so perhaps it'd be possible to make it depend on HAS_DMA.

VIDEOBUF2_DMA_CONTIG already depends on HAS_DMA, but when driver use select
directive for enabling support for VIDEOBUF2_DMA_CONTIG, the dependencies
are not checked further. This is known limitation/feature of kconfig system.

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland