linux-kernel - Re: [PATCH v4 16/19] ARM: LPAE: Use generic dma_addr

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Message-ID: <20110212103413.GD15616@n2100.arm.linux.org.uk>
Date:	Sat, 12 Feb 2011 10:34:13 +0000
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Catalin Marinas <catalin.marinas@....com>
Cc:	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Will Deacon <will.deacon@....com>
Subject: Re: [PATCH v4 16/19] ARM: LPAE: Use generic dma_addr_t type
	definition

On Mon, Jan 24, 2011 at 05:55:58PM +0000, Catalin Marinas wrote:
> From: Will Deacon <will.deacon@....com>
> 
> This patch uses the types.h implementation in asm-generic to define the
> dma_addr_t type as the same width as phys_addr_t.
> 
> NOTE: this is a temporary patch until the corresponding patches unifying
> the dma_addr_t and removing the dma64_addr_t are merged into mainline.

I'm not too sure about this patch.  All of the DMA devices we have only
take 32-bit addresses for their DMA, so making dma_addr_t 64-bit seems
wrong as we'll implicitly truncate these addresses.

As ARM platforms don't (sanely) support DMA, I think dropping this patch
for the time being would be a good idea, and stick with 32-bit dma_addr_t,
especially as we need to first do a sweep for dma_addr_t usage in device
driver structures (such as dma engine scatter lists.)  These really should
use __le32/__be32/u32 depending on whether they're little endian, big
endian or native endian.
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