linux-kernel - Re: [PATCH 0/4] dma-mapping: Constify dma

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Date:	Wed, 25 May 2016 14:37:13 +0200
From:	Krzysztof Kozlowski <k.kozlowski@...sung.com>
To:	Christoph Hellwig <hch@...radead.org>
Cc:	Russell King <linux@...linux.org.uk>,
	Stefano Stabellini <sstabellini@...nel.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	Joerg Roedel <joro@...tes.org>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	xen-devel@...ts.xenproject.org, iommu@...ts.linux-foundation.org,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
Subject: Re: [PATCH 0/4] dma-mapping: Constify dma_attrs

On 05/24/2016 11:09 AM, Christoph Hellwig wrote:
> I think this is moving into the wrong direction.  The right fix here
> is to get of all the dma_attrs boilerplate code and just replace it
> with a simple enum dma_flags.  This would simplify both the callers
> and most importantly the wrappers for the flag-less versions a lot.

The dma attrs are additive so maybe not an enum but an unsigned long and
#defines:

#define	DMA_ATTR_WRITE_BARRIER		0x0001u
#define DMA_ATTR_WEAK_ORDERING		0x0002u
#define DMA_ATTR_WRITE_COMBINE		0x0004u
...

The intrusiveness of it would be similar but indeed looks simpler - when
reading the code and when setting the dma_attrs.

If that seems reasonable, I will send a follow up with new approach.

Thanks for feedback!

Best regards,
Krzysztof