linux-kernel - Re: [PATCH 3/3] videobuf2: replace a layering violation with dma_map

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Message-ID: <20190114103139.GA31005@lst.de>
Date:   Mon, 14 Jan 2019 11:31:39 +0100
From:   Christoph Hellwig <hch@....de>
To:     Mauro Carvalho Chehab <mchehab+samsung@...nel.org>
Cc:     Christoph Hellwig <hch@....de>, Pawel Osciak <pawel@...iak.com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Niklas Söderlund 
        <niklas.soderlund+renesas@...natech.se>,
        Russell King <linux@...linux.org.uk>,
        iommu@...ts.linux-foundation.org,
        linux-arm-kernel@...ts.infradead.org,
        linuxppc-dev@...ts.ozlabs.org, linux-media@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] videobuf2: replace a layering violation with
 dma_map_resource

On Fri, Jan 11, 2019 at 05:54:16PM -0200, Mauro Carvalho Chehab wrote:
> Em Fri, 11 Jan 2019 19:17:31 +0100
> Christoph Hellwig <hch@....de> escreveu:
> 
> > vb2_dc_get_userptr pokes into arm direct mapping details to get the
> > resemblance of a dma address for a a physical address that does is
> > not backed by a page struct.  Not only is this not portable to other
> > architectures with dma direct mapping offsets, but also not to uses
> > of IOMMUs of any kind.  Switch to the proper dma_map_resource /
> > dma_unmap_resource interface instead.
> 
> Makes sense to me. I'm assuming that you'll be pushing it together
> with other mm patches, so:

Not really mm, but rather DMA mapping, but yes, I'd love to take it
all together.

Thanks!