Re: [PATCH 1/2] V4L/DVB: buf-dma-sg.c: don't assume nr_pages == sglen

[Sakari Ailus <sakari.ailus@maxwell.research.nokia.com>]

Hi Arnout,

Arnout Vandecappelle wrote:
> videobuf_pages_to_sg() and videobuf_vmalloc_to_sg() happen to create
> a scatterlist element for every page.  However, this is not true for
> bus addresses, so other functions shouldn't rely on the length of the
> scatter list being equal to nr_pages.
> ---
>  drivers/media/video/videobuf-dma-sg.c |    6 +++---
>  1 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/media/video/videobuf-dma-sg.c b/drivers/media/video/videobuf-dma-sg.c
> index da1790e..3b6f1b8 100644
> --- a/drivers/media/video/videobuf-dma-sg.c
> +++ b/drivers/media/video/videobuf-dma-sg.c
> @@ -244,7 +244,7 @@ int videobuf_dma_map(struct videobuf_queue* q, struct videobuf_dmabuf *dma)
>  	}
>  	if (!dma->bus_addr) {
>  		dma->sglen = dma_map_sg(q->dev, dma->sglist,
> -					dma->nr_pages, dma->direction);
> +					dma->sglen, dma->direction);
>  		if (0 == dma->sglen) {
>  			printk(KERN_WARNING
>  			       "%s: videobuf_map_sg failed\n",__func__);

Where is dma->sglen actually set?

videobuf_dma_map() is used in __videobuf_iolock
(drivers/media/video/videobuf-dma-sg.c) but neither
videobuf_dma_init_kernel() nor videobuf_dma_init_user() seem to set it.
This apparently leaves the value uninitialised.

I definitely think it should be assigned somewhere. :-)

-- 
Sakari Ailus
sakari.ailus@maxwell.research.nokia.com