linux-kernel - [PATCH v2 1/1] V4L: videobuf, don't use dma addr as physical

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Message-Id: <1298967701-11889-1-git-send-email-jslaby@suse.cz>
Date:	Tue,  1 Mar 2011 09:21:41 +0100
From:	Jiri Slaby <jslaby@...e.cz>
To:	mchehab@...radead.org
Cc:	linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
	jirislaby@...il.com, Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Subject: [PATCH v2 1/1] V4L: videobuf, don't use dma addr as physical

mem->dma_handle is a dma address obtained by dma_alloc_coherent which
needn't be a physical address as a hardware IOMMU can (and most
likely will) return a bus address where physical != bus address. So
ensure we are remapping (remap_pfn_range) the right page in
__videobuf_mmap_mapper by using virt_to_phys(mem->vaddr) and not
mem->dma_handle.

While at it, use PFN_DOWN instead of explicit shift to obtain a frame
number.

This was discovered by a random review of the code when looking for
something completely different. I'm not aware of any bug reports for
this.

However it is a bug because many v4l drivers use this layer and have
no idea whether IOMMU is in the system and running or not.

Signed-off-by: Jiri Slaby <jslaby@...e.cz>
Cc: Mauro Carvalho Chehab <mchehab@...radead.org>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
---

This is a version with updated changelog.

 drivers/media/video/videobuf-dma-contig.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/drivers/media/video/videobuf-dma-contig.c b/drivers/media/video/videobuf-dma-contig.c
index c969111..19d3e4a 100644
--- a/drivers/media/video/videobuf-dma-contig.c
+++ b/drivers/media/video/videobuf-dma-contig.c
@@ -300,7 +300,7 @@ static int __videobuf_mmap_mapper(struct videobuf_queue *q,

 	vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
 	retval = remap_pfn_range(vma, vma->vm_start,
-				 mem->dma_handle >> PAGE_SHIFT,
+				 PFN_DOWN(virt_to_phys(mem->vaddr))
 				 size, vma->vm_page_prot);
 	if (retval) {
 		dev_err(q->dev, "mmap: remap failed with error %d. ", retval);
-- 
1.7.4.1

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