linux-kernel - RE: [GIT PULL] CMA and ARM DMA-mapping updates for v3.5

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Date:	Tue, 29 May 2012 16:50:45 +0200
From:	Marek Szyprowski <m.szyprowski@...sung.com>
To:	'Russell King - ARM Linux' <linux@....linux.org.uk>
Cc:	'Linus Torvalds' <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	'Arnd Bergmann' <arnd@...db.de>,
	'Andrew Morton' <akpm@...ux-foundation.org>,
	linaro-mm-sig@...ts.linaro.org,
	'Michal Nazarewicz' <mina86@...a86.com>,
	'Kyungmin Park' <kyungmin.park@...sung.com>
Subject: RE: [GIT PULL] CMA and ARM DMA-mapping updates for v3.5

Hello,

On Tuesday, May 29, 2012 2:30 PM Russell King - ARM Linux wrote:

> I notice we have new warnings as a result of CMA being merged, though
> thankfully they're just in Kconfig:
> 
> warning: (ARM) selects CMA which has unmet direct dependencies (HAVE_DMA_CONTIGUOUS &&
> HAVE_MEMBLOCK && EXPERIMENTAL)
> 
> This seems totally weird: you're mandating that ARM must have CMA
> selected, but it's an experimental feature?  So you're implying that
> the entire ARM kernel becomes totally experimental for the next
> release cycle?
> 
> I think this needs fixing.

No, that wasn't my intention. I will provide a patch which removes unconditional dependency
on CMA - it will let one to disable CMA and use old allocation method if needed, but this 
requires a few more changes in the dma-mapping implementation. I wasn't aware of the 
consequences and no one has complained about this since v15 of CMA patches (Aug 2011).

Best regards
-- 
Marek Szyprowski
Samsung Poland R&D Center


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