linux-kernel - Re: [PATCH v5 2/7] dma: Add simple dma_noop

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Date:   Thu, 22 Jun 2017 13:46:09 +0100
From:   Vladimir Murzin <vladimir.murzin@....com>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux@...linux.org.uk, sza@....hu, arnd@...db.de,
        gregkh@...uxfoundation.org, akpm@...ux-foundation.org,
        alexandre.torgue@...com, robin.murphy@....com,
        benjamin.gaignard@...aro.org, kbuild-all@...org,
        Joerg Roedel <jroedel@...e.de>,
        Christian Borntraeger <borntraeger@...ibm.com>
Subject: Re: [PATCH v5 2/7] dma: Add simple dma_noop_mmap

On 20/06/17 14:23, Christoph Hellwig wrote:
> On Wed, May 24, 2017 at 11:24:27AM +0100, Vladimir Murzin wrote:
>> This patch adds a simple implementation of mmap to dma_noop_ops.
> 
> Currently we use dma_common_mmap as the generic fallback if a dma_ops
> instance doesn't implement a mmap method.  Can you just fix up
> dma_common_mmap for your nommu case - it looks like yours is basically
> a subset.

dma_common_map() is guarded with CONFIG_MMU and I'm not dare to change that
since I have no idea 1) why it was done 2) how it affects other arches :(

> 
> In fact I suspect yours should call dma_mmap_from_coherent as well,
> so the only different is the lack of pgprot_noncached call.
> 

OK, I'll add a call to dma_mmap_from_coherent().

Cheers
Vladimir