It is not a theoretically issue, it is a real case that the mapping failed issue happens in 3.14.y kernel but not happens in previous 3.10.y kernel. So I need your confirmation on it. Thanks. Best regards, Fancy Fang -----Original Message----- From: Hans Verkuil [mailto:hverkuil@xxxxxxxxx] Sent: Wednesday, September 10, 2014 3:01 PM To: Fang Chen-B47543; m.chehab@xxxxxxxxxxx; viro@xxxxxxxxxxxxxxxxxx Cc: Guo Shawn-R65073; linux-media@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Marek Szyprowski Subject: Re: [PATCH] [media] videobuf-dma-contig: replace vm_iomap_memory() with remap_pfn_range(). On 09/10/14 07:28, Fancy Fang wrote: > When user requests V4L2_MEMORY_MMAP type buffers, the videobuf-core > will assign the corresponding offset to the 'boff' field of the > videobuf_buffer for each requested buffer sequentially. Later, user > may call mmap() to map one or all of the buffers with the 'offset' > parameter which is equal to its 'boff' value. Obviously, the 'offset' > value is only used to find the matched buffer instead of to be the > real offset from the buffer's physical start address as used by > vm_iomap_memory(). So, in some case that if the offset is not zero, > vm_iomap_memory() will fail. Is this just a fix for something that can fail theoretically, or do you actually have a case where this happens? I am very reluctant to make any changes to videobuf. Drivers should all migrate to vb2. I have CC-ed Marek as well since he knows a lot more about this stuff than I do. Regards, Hans > > Signed-off-by: Fancy Fang <chen.fang@xxxxxxxxxxxxx> > --- > drivers/media/v4l2-core/videobuf-dma-contig.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/drivers/media/v4l2-core/videobuf-dma-contig.c > b/drivers/media/v4l2-core/videobuf-dma-contig.c > index bf80f0f..8bd9889 100644 > --- a/drivers/media/v4l2-core/videobuf-dma-contig.c > +++ b/drivers/media/v4l2-core/videobuf-dma-contig.c > @@ -305,7 +305,9 @@ static int __videobuf_mmap_mapper(struct videobuf_queue *q, > /* Try to remap memory */ > size = vma->vm_end - vma->vm_start; > vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot); > - retval = vm_iomap_memory(vma, mem->dma_handle, size); > + retval = remap_pfn_range(vma, vma->vm_start, > + mem->dma_handle >> PAGE_SHIFT, > + size, vma->vm_page_prot); > if (retval) { > dev_err(q->dev, "mmap: remap failed with error %d. ", > retval); > -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
