Hi Tomasz,
Thanks for the patch.
On Tuesday 02 October 2012 16:27:32 Tomasz Stanislawski wrote:
> This patch adds taking reference to the device for MMAP buffers.
>
> Such buffers, may be exported using DMABUF mechanism. If the driver that
> created a queue is unloaded then the queue is released, the device might be
> released too. However, buffers cannot be released if they are referenced by
> DMABUF descriptor(s). The device pointer kept in a buffer must be valid for
> the whole buffer's lifetime. Therefore MMAP buffers should take a reference
> to the device to avoid risk of dangling pointers.
>
> Signed-off-by: Tomasz Stanislawski <t.stanislaws@xxxxxxxxxxx>
>
> ---
> drivers/media/video/videobuf2-dma-contig.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/drivers/media/video/videobuf2-dma-contig.c
> b/drivers/media/video/videobuf2-dma-contig.c index b138b5c..b4d287a 100644
> --- a/drivers/media/video/videobuf2-dma-contig.c
> +++ b/drivers/media/video/videobuf2-dma-contig.c
> @@ -148,6 +148,7 @@ static void vb2_dc_put(void *buf_priv)
> kfree(buf->sgt_base);
> }
> dma_free_coherent(buf->dev, buf->size, buf->vaddr, buf->dma_addr);
> + put_device(buf->dev);
> kfree(buf);
> }
>
> @@ -161,9 +162,13 @@ static void *vb2_dc_alloc(void *alloc_ctx, unsigned
> long size) if (!buf)
> return ERR_PTR(-ENOMEM);
>
> + /* prevent the device from release while the buffer is exported */
> + get_device(dev);
> +
What about moving this below the dma_alloc_coherent() call ? You could then
avoid the put_device() call in the error path.
> buf->vaddr = dma_alloc_coherent(dev, size, &buf->dma_addr, GFP_KERNEL);
> if (!buf->vaddr) {
> dev_err(dev, "dma_alloc_coherent of size %ld failed\n", size);
> + put_device(dev);
> kfree(buf);
> return ERR_PTR(-ENOMEM);
> }
Something like
- buf->dev = dev;
+ buf->dev = get_device(dev);
buf->size = size
--
Regards,
Laurent Pinchart
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