From: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
To: alan@lxorguk.ukuu.org.uk
Cc: fujita.tomonori@lab.ntt.co.jp, zpfeffer@codeaurora.org,
joro@8bytes.org, dwalker@codeaurora.org, andi@firstfloor.org,
randy.dunlap@oracle.com, mel@csn.ul.ie, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org,
linux-omap@vger.kernel.org, linux-arm-kernel@lists.infradead.org
Subject: Re: [RFC 3/3] mm: iommu: The Virtual Contiguous Memory Manager
Date: Tue, 13 Jul 2010 17:45:39 +0900 [thread overview]
Message-ID: <20100713174519D.fujita.tomonori@lab.ntt.co.jp> (raw)
In-Reply-To: <20100713094244.7eb84f1b@lxorguk.ukuu.org.uk>
On Tue, 13 Jul 2010 09:42:44 +0100
Alan Cox <alan@lxorguk.ukuu.org.uk> wrote:
> On Tue, 13 Jul 2010 17:30:43 +0900
> FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp> wrote:
>
> > On Tue, 13 Jul 2010 09:20:12 +0100
> > Alan Cox <alan@lxorguk.ukuu.org.uk> wrote:
> >
> > > > Why video4linux can't use the DMA API? Doing DMA with vmalloc'ed
> > > > buffers is a thing that we should avoid (there are some exceptions
> > > > like xfs though).
> > >
> > > Vmalloc is about the only API for creating virtually linear memory areas.
> > > The video stuff really needs that to avoid lots of horrible special cases
> > > when doing buffer processing and the like.
> > >
> > > Pretty much each driver using it has a pair of functions 'rvmalloc' and
> > > 'rvfree' so given a proper "vmalloc_for_dma()" type interface can easily
> > > be switched
> >
> > We already have helper functions for DMA with vmap pages,
> > flush_kernel_vmap_range and invalidate_kernel_vmap_range.
>
> I'm not sure they help at all because the DMA user for these pages isn't
> the video driver - it's the USB layer, and the USB layer isn't
> specifically aware it is being passed vmap pages.
Drivers can tell the USB layer that these are vmapped buffers? Adding
something to struct urb? I might be totally wrong since I don't know
anything about the USB layer.
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next prev parent reply other threads:[~2010-07-13 8:46 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-06-30 5:55 [RFC 1/3] mm: iommu: An API to unify IOMMU, CPU and device memory management Zach Pfeffer
2010-06-30 5:55 ` [RFC 2/3] mm: iommu: A physical allocator for the VCMM Zach Pfeffer
2010-06-30 5:55 ` [RFC 3/3] mm: iommu: The Virtual Contiguous Memory Manager Zach Pfeffer
2010-07-01 17:17 ` Randy Dunlap
2010-07-01 18:02 ` Andi Kleen
2010-07-01 19:28 ` Daniel Walker
2010-07-01 19:38 ` Andi Kleen
2010-07-01 19:42 ` Daniel Walker
2010-07-01 22:15 ` Hari Kanigeri
2010-07-02 7:09 ` Zach Pfeffer
2010-07-10 14:36 ` Joerg Roedel
2010-07-13 5:21 ` Zach Pfeffer
2010-07-14 19:34 ` Joerg Roedel
2010-07-15 1:18 ` Zach Pfeffer
2010-07-01 22:00 ` Zach Pfeffer
2010-07-01 22:05 ` Daniel Walker
2010-07-02 7:33 ` Zach Pfeffer
2010-07-10 14:56 ` Joerg Roedel
2010-07-13 5:46 ` Zach Pfeffer
2010-07-13 5:59 ` FUJITA Tomonori
2010-07-13 8:20 ` Alan Cox
2010-07-13 8:30 ` FUJITA Tomonori
2010-07-13 8:42 ` Alan Cox
2010-07-13 8:45 ` FUJITA Tomonori [this message]
2010-07-13 9:02 ` Russell King - ARM Linux
2010-07-14 1:59 ` FUJITA Tomonori
2010-07-22 3:50 ` Zach Pfeffer
2010-07-22 4:47 ` FUJITA Tomonori
2010-07-22 16:33 ` Zach Pfeffer
2010-07-22 7:51 ` Russell King - ARM Linux
2010-07-22 16:13 ` Zach Pfeffer
2010-07-13 12:06 ` Zach Pfeffer
2010-07-01 22:51 ` Hari Kanigeri
2010-07-02 7:29 ` Zach Pfeffer
2010-07-01 23:00 ` Andi Kleen
2010-07-02 6:17 ` Zach Pfeffer
2010-07-02 8:22 ` Andi Kleen
2010-07-02 18:42 ` Zach Pfeffer
2010-07-10 15:11 ` Joerg Roedel
2010-07-13 5:52 ` Zach Pfeffer
2010-07-03 6:36 ` Zach Pfeffer
2010-07-10 14:54 ` Joerg Roedel
2010-07-13 5:27 ` Zach Pfeffer
2010-07-01 20:59 ` Paul Walmsley
2010-07-01 21:48 ` Randy Dunlap
2010-06-30 23:40 ` [RFC 1/3] mm: iommu: An API to unify IOMMU, CPU and device memory management Randy Dunlap
2010-07-01 7:16 ` Zach Pfeffer
2010-07-02 7:00 ` Paul Mundt
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