Re: [PATCHv3 01/12] vb2: add a dev field to use for the default allocation context

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Hans,

On Saturday 23 Apr 2016 12:37:10 Hans Verkuil wrote:
> On 04/23/2016 02:14 AM, Laurent Pinchart wrote:
> > On Friday 22 Apr 2016 10:38:08 Hans Verkuil wrote:
> >> From: Hans Verkuil <hans.verkuil@cisco.com>
> >> 
> >> The allocation context is nothing more than a per-plane device pointer
> >> to use when allocating buffers. So just provide a dev pointer in
> >> vb2_queue for that purpose and drivers can skip
> >> allocating/releasing/filling in the allocation context unless they
> >> require different per-plane device pointers as used by some Samsung
> >> SoCs.
> >> 
> >> Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
> >> Cc: Laurent Pinchart <Laurent.pinchart@ideasonboard.com>
> >> Cc: Sakari Ailus <sakari.ailus@iki.fi>
> >> Cc: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
> >> Cc: Florian Echtler <floe@butterbrot.org>
> >> Cc: Federico Vaga <federico.vaga@gmail.com>
> >> Cc: "Lad, Prabhakar" <prabhakar.csengg@gmail.com>
> >> Cc: Scott Jiang <scott.jiang.linux@gmail.com>
> >> Cc: Philipp Zabel <p.zabel@pengutronix.de>
> >> Cc: Fabien Dessenne <fabien.dessenne@st.com>
> >> Cc: Benoit Parrot <bparrot@ti.com>
> >> Cc: Mikhail Ulyanov <mikhail.ulyanov@cogentembedded.com>
> >> Cc: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
> >> Cc: Javier Martin <javier.martin@vista-silicon.com>
> >> Cc: Jonathan Corbet <corbet@lwn.net>
> >> Cc: Ludovic Desroches <ludovic.desroches@atmel.com>
> >> Cc: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
> >> Cc: Kyungmin Park <kyungmin.park@samsung.com>
> >> Cc: Sylwester Nawrocki <s.nawrocki@samsung.com>
> >> ---
> >> 
> >>  drivers/media/v4l2-core/videobuf2-core.c | 16 +++++++++-------
> >>  include/media/videobuf2-core.h           |  3 +++
> >>  2 files changed, 12 insertions(+), 7 deletions(-)
> >> 
> >> diff --git a/drivers/media/v4l2-core/videobuf2-core.c
> >> b/drivers/media/v4l2-core/videobuf2-core.c index 5d016f4..88b5e48 100644
> >> --- a/drivers/media/v4l2-core/videobuf2-core.c
> >> +++ b/drivers/media/v4l2-core/videobuf2-core.c
> >> @@ -206,8 +206,9 @@ static int __vb2_buf_mem_alloc(struct vb2_buffer *vb)
> >> 
> >>  	for (plane = 0; plane < vb->num_planes; ++plane) {
> >>  	
> >>  		unsigned long size = PAGE_ALIGN(vb->planes[plane].length);
> >> 
> >> -		mem_priv = call_ptr_memop(vb, alloc, q->alloc_ctx[plane],
> >> -				      size, dma_dir, q->gfp_flags);
> >> +		mem_priv = call_ptr_memop(vb, alloc,
> >> +				q->alloc_ctx[plane] ? : &q->dev,
> >> +				size, dma_dir, q->gfp_flags);
> > 
> > While the videobuf2-dma-sg allocation context indeed only contains a
> > pointer to the device, the videobuf2-dma-contig context also contains a
> > dma_attrs. This patch will break the videobuf2-dma-contig alloc
> > implementation.
>
> Good point. I fixed this in the last patch, but that would mean dma-contig
> would be broken for the patches in between.
> 
> I'm moving dma_attrs to struct vb2_queue as the first patch, then the rest
> will work fine.

Couldn't a driver require different dma attributes per plane ? Would it make 
sense to keep the allocation context structure, and use the struct device and 
dma attributes stored in the queue when no allocation context is provided ?

> I've also taken care of the vsp1_video comments.

Thank you.

-- 
Regards,

Laurent Pinchart