[PATCHv10 21/26] v4l: vb2-dma-contig: add reference counting for a device from allocator context

[Laurent Pinchart]

Hi Tomasz,

Thanks for the patch.

On Wednesday 10 October 2012 16:46:40 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 at samsung.com>
> Acked-by: Hans Verkuil <hans.verkuil at cisco.com>

Acked-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>

But two small comments below.

> ---
>  drivers/media/v4l2-core/videobuf2-dma-contig.c |    4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/media/v4l2-core/videobuf2-dma-contig.c
> b/drivers/media/v4l2-core/videobuf2-dma-contig.c index b138b5c..2d661fd
> 100644
> --- a/drivers/media/v4l2-core/videobuf2-dma-contig.c
> +++ b/drivers/media/v4l2-core/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);
>  }
> 
> @@ -168,6 +169,9 @@ static void *vb2_dc_alloc(void *alloc_ctx, unsigned long
> size) return ERR_PTR(-ENOMEM);
>  	}
> 
> +	/* prevent the device from release while the buffer is exported */

s/prevent/Prevent/ ?

> +	get_device(dev);
> +
>  	buf->dev = dev;

What about just

	buf->dev = get_device(dev);

>  	buf->size = size;
-- 
Regards,

Laurent Pinchart