Date: Thu, 28 Apr 2011 10:42:15 +0100
From: Russell King - ARM Linux <linux@arm.linux.org.uk>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Arnd Bergmann <arnd@arndb.de>, linaro-mm-sig@lists.linaro.org,
        linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org
Subject: Re: [RFC] ARM DMA mapping TODO, v1
Message-ID: <20110428094215.GW17290@n2100.arm.linux.org.uk>
References: <201104212129.17013.arnd@arndb.de> <1303939866.2513.180.camel@pasglop>
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On Thu, Apr 28, 2011 at 07:31:06AM +1000, Benjamin Herrenschmidt wrote:
> The question remains, if we ever want to do more complex demand-paged
> operations, should we also expose a lower level set of functions to get
> struct page out of a dma_alloc_coherent() allocation and to get the
> pgprot for the user dma mapping ?

I don't think so - that places the requirement that dma_alloc_coherent()
must be backed by memory with a set of struct page, which may not always
be the case.

Think about dma_alloc_coherent() with dma_declare_coherent_memory() used
with memory which is not part of system RAM.
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