linux-kernel - Re: [RFC][PATCH 12/15] videobuf2: add begin/end cpu

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Message-ID: <20200122063714.GA14881@google.com>
Date:   Wed, 22 Jan 2020 15:37:14 +0900
From:   Sergey Senozhatsky <senozhatsky@...omium.org>
To:     Hans Verkuil <hverkuil@...all.nl>
Cc:     Sergey Senozhatsky <senozhatsky@...omium.org>,
        Hans Verkuil <hans.verkuil@...co.com>,
        Tomasz Figa <tfiga@...omium.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Sakari Ailus <sakari.ailus@....fi>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Pawel Osciak <posciak@...omium.org>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC][PATCH 12/15] videobuf2: add begin/end cpu_access callbacks
 to dma-sg

On (20/01/10 11:13), Hans Verkuil wrote:
> On 12/17/19 4:20 AM, Sergey Senozhatsky wrote:
> > Provide begin_cpu_access() and end_cpu_access() dma_buf_ops
> > callbacks for cache synchronisation on exported buffers.
> > 
> > Signed-off-by: Sergey Senozhatsky <senozhatsky@...omium.org>
> > ---
> >  .../media/common/videobuf2/videobuf2-dma-sg.c | 22 +++++++++++++++++++
> >  1 file changed, 22 insertions(+)
> > 
> > diff --git a/drivers/media/common/videobuf2/videobuf2-dma-sg.c b/drivers/media/common/videobuf2/videobuf2-dma-sg.c
> > index 6db60e9d5183..bfc99a0cb7b9 100644
> > --- a/drivers/media/common/videobuf2/videobuf2-dma-sg.c
> > +++ b/drivers/media/common/videobuf2/videobuf2-dma-sg.c
> > @@ -470,6 +470,26 @@ static void vb2_dma_sg_dmabuf_ops_release(struct dma_buf *dbuf)
> >  	vb2_dma_sg_put(dbuf->priv);
> >  }
> >  
> 
> There is no corresponding vb2_sg_buffer_consistent function here.
> 
> Looking more closely I see that vb2_dma_sg_alloc doesn't pass the dma_attrs
> argument to dma_map_sg_attrs, thus V4L2_FLAG_MEMORY_NON_CONSISTENT has no
> effect on dma-sg buffers.
> 
> Is there a reason why dma_attrs isn't passed on to dma_map_sg_attrs()?

Laziness.

> I suspect it was just laziness in the past, and that it should be wired
> up, just as for dma-contig.

OK, I can include it into v2.

	-ss