linux-kernel - Re: [PATCH 2/8] dmaengine: mv_xor: add support for a38x command in descriptor mode

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Date:	Wed, 13 May 2015 10:46:45 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Maxime Ripard <maxime.ripard@...e-electrons.com>
Cc:	linux-arm-kernel@...ts.infradead.org,
	Vinod Koul <vinod.koul@...el.com>,
	Dan Williams <dan.j.williams@...el.com>,
	Gregory Clement <gregory.clement@...e-electrons.com>,
	Jason Cooper <jason@...edaemon.net>,
	Andrew Lunn <andrew@...n.ch>,
	Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>,
	Lior Amsalem <alior@...vell.com>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	Thomas Petazzoni <thomas@...e-electrons.com>,
	linux-kernel@...r.kernel.org, linux-crypto@...r.kernel.org,
	dmaengine@...r.kernel.org, "David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH 2/8] dmaengine: mv_xor: add support for a38x command in descriptor mode

On Wednesday 13 May 2015 10:15:35 Maxime Ripard wrote:
> > Alternatively, you could leave the XOR_DESCRIPTOR_SWAP flag disabled
> > and just swap the descriptors manually like a lot of other drivers
> > do. You have to swap the mmio accesses anywya.
> 
> That won't be easily doable however.
> 
> Not only the endianness of the individual fields in the descriptor
> changes, but changing the endianness also swaps the fields themselves
> by pair of u32.
> 
> You can see that here:
> http://lxr.free-electrons.com/source/drivers/dma/mv_xor.h#L159
> 
> So I'm guessing that leaving it like it is was the more readable
> solution.

I see, yes that would get a bit ugly.

	Arnd
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