linux-kernel - Re: [RFC v2] dma-mapping: Use unsigned long for dma

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Date:	Wed, 1 Jun 2016 00:51:42 -0700
From:	Christoph Hellwig <hch@...radead.org>
To:	Krzysztof Kozlowski <k.kozlowski@...sung.com>
Cc:	Christoph Hellwig <hch@...radead.org>,
	Russell King <linux@...linux.org.uk>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>,
	Joerg Roedel <joro@...tes.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Michal Hocko <mhocko@...e.com>,
	Mel Gorman <mgorman@...hsingularity.net>,
	Arnd Bergmann <arnd@...db.de>,
	Andy Lutomirski <luto@...nel.org>, linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	xen-devel@...ts.xenproject.org, dri-devel@...ts.freedesktop.org,
	linux-samsung-soc@...r.kernel.org,
	iommu@...ts.linux-foundation.org, sstabellini@...nel.org,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
Subject: Re: [RFC v2] dma-mapping: Use unsigned long for dma_attrs

On Wed, Jun 01, 2016 at 07:36:42AM +0200, Krzysztof Kozlowski wrote:
> > No really for this patch, but I would much prefer to document them next
> > to the code in the long run.  Also I really think these BIT() macros
> > are a distraction compared to the (1 << N) notation.
> 
> Not much difference to me but maybe plain number:
> ...	0x01u
> ...	0x02u
> ?

I prefer the little bit shifts, but even the explicit values are much
better than the obsfucating macros :)  Anyway, your patch and in the end
all three methods will get the work done.

> > I'd just kill this helper, much easier to simply open code it in the
> > caller.
> 
> Keeping it for now helps reducing the number of changes in the patch.
> The patch will be quite big as it has to replace all the uses atomically.
> 
> I can get rid of the helper in consecutive patch.

Sounds fine.