Re: RFC: vb2: replace alloc_ctx by struct device * in vb2_queue

[Marek Szyprowski <m.szyprowski@samsung.com>]

Hello,

On 2014-09-21 15:05, Hans Verkuil wrote:
> Hi Marek, Pawel,
>
> Currently for dma_config (and the dma_sg code that I posted before) drivers have
> to allocate a alloc_ctx context, but in practice that just contains a device pointer.
>
> Is there any reason why we can't just change in struct vb2_queue:
>
> 	void                            *alloc_ctx[VIDEO_MAX_PLANES];
>
> to:
>
> 	struct device                   *alloc_ctx[VIDEO_MAX_PLANES];
>
> or possibly even just:
>
> 	struct device                   *alloc_ctx;
>
> That simplifies the code quite a bit and I don't see and need for anything
> else. The last option would make it impossible to have different allocation
> contexts for different planes, but that might be something that Samsumg needs.

The last option won't work for for s5p-mfc driver, so better please keep
separate context per each plane.

If we are going to change the structures and their names, then maybe we 
should
get rid of 'context' name are simply replace it by the following entry in
vb2_queue:

struct device  *alloc_dev[VIDEO_MAX_PLANES];


and change respective parameter names in memory allocators.

The true context was useful when we were using custom, non-mainline memory
allocators.

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland