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Date: Wed, 23 Dec 2009 17:01:10 +0100
From: Matthieu CASTET <matthieu.castet@parrot.com>
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To: v4l2_linux <linux-media@vger.kernel.org>
Subject: videobuf-dma-contig.c cached user mapping
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Hi,

I would like to add support for cached user mapping to
videobuf-dma-contig.c.

For enabling this, "vma->vm_page_prot =
pgprot_noncached(vma->vm_page_prot);" line should be removed.

But now we should ensure user mapping cache coherency.
For that, for a camera we should :
- invalidate cache before dma operation (to have not old buffer data in
the cache)
- forbid the user to access the buffer during the dma operation (to not
pollute the cache)

Is it possible ?
How can we achieve that ?

I see sync method, that seems only called after frame capture ?


Thanks,
Matthieu