linux-kernel - Re: [PATCH 6/9] media: cedrus: Add ops structure

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Message-ID: <20180625132933.tzr36vsucqsq3mmb@flea>
Date:   Mon, 25 Jun 2018 15:29:33 +0200
From:   Maxime Ripard <maxime.ripard@...tlin.com>
To:     Paul Kocialkowski <paul.kocialkowski@...tlin.com>
Cc:     hans.verkuil@...co.com, acourbot@...omium.org,
        sakari.ailus@...ux.intel.com,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        tfiga@...omium.org, posciak@...omium.org,
        Chen-Yu Tsai <wens@...e.org>, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-media@...r.kernel.org,
        nicolas.dufresne@...labora.com, jenskuske@...il.com,
        linux-sunxi@...glegroups.com,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH 6/9] media: cedrus: Add ops structure

Hi!

On Thu, Jun 21, 2018 at 11:49:54AM +0200, Paul Kocialkowski wrote:
> Hi,
> 
> On Wed, 2018-06-13 at 16:07 +0200, Maxime Ripard wrote:
> > In order to increase the number of codecs supported, we need to decouple
> > the MPEG2 only code that was there up until now and turn it into something
> > a bit more generic.
> > 
> > Do that by introducing an intermediate ops structure that would need to be
> > filled by each supported codec. Start by implementing in that structure the
> > setup and trigger hooks that are currently the only functions being
> > implemented by codecs support.
> > 
> > To do so, we need to store the current codec in use, which we do at
> > start_streaming time.
> 
> With the comments below taken in account, this is:
> 
> Acked-by: Paul Kocialkowski <paul.kocialkowski@...tlin.com>

Thanks!

> > Signed-off-by: Maxime Ripard <maxime.ripard@...tlin.com>
> > ---
> >  .../platform/sunxi/cedrus/sunxi_cedrus.c      |  2 ++
> >  .../sunxi/cedrus/sunxi_cedrus_common.h        | 11 +++++++
> >  .../platform/sunxi/cedrus/sunxi_cedrus_dec.c  | 10 +++---
> >  .../sunxi/cedrus/sunxi_cedrus_mpeg2.c         | 11 +++++--
> >  .../sunxi/cedrus/sunxi_cedrus_mpeg2.h         | 33 -------------------
> >  .../sunxi/cedrus/sunxi_cedrus_video.c         | 17 +++++++++-
> >  6 files changed, 42 insertions(+), 42 deletions(-)
> >  delete mode 100644 drivers/media/platform/sunxi/cedrus/sunxi_cedrus_mpeg2.h
> > 
> > diff --git a/drivers/media/platform/sunxi/cedrus/sunxi_cedrus.c b/drivers/media/platform/sunxi/cedrus/sunxi_cedrus.c
> > index ccd41d9a3e41..bc80480f5dfd 100644
> > --- a/drivers/media/platform/sunxi/cedrus/sunxi_cedrus.c
> > +++ b/drivers/media/platform/sunxi/cedrus/sunxi_cedrus.c
> > @@ -244,6 +244,8 @@ static int sunxi_cedrus_probe(struct platform_device *pdev)
> >  	if (ret)
> >  		return ret;
> >  
> > +	dev->dec_ops[SUNXI_CEDRUS_CODEC_MPEG2] = &sunxi_cedrus_dec_ops_mpeg2;
> > +
> >  	ret = v4l2_device_register(&pdev->dev, &dev->v4l2_dev);
> >  	if (ret)
> >  		goto unreg_media;
> > diff --git a/drivers/media/platform/sunxi/cedrus/sunxi_cedrus_common.h b/drivers/media/platform/sunxi/cedrus/sunxi_cedrus_common.h
> > index a5f83c452006..c2e2c92d103b 100644
> > --- a/drivers/media/platform/sunxi/cedrus/sunxi_cedrus_common.h
> > +++ b/drivers/media/platform/sunxi/cedrus/sunxi_cedrus_common.h
> > @@ -75,6 +75,7 @@ struct sunxi_cedrus_ctx {
> >  	struct v4l2_pix_format_mplane src_fmt;
> >  	struct sunxi_cedrus_fmt *vpu_dst_fmt;
> >  	struct v4l2_pix_format_mplane dst_fmt;
> > +	enum sunxi_cedrus_codec current_codec;
> 
> Nit: for consistency with the way things are named, "codec_current"
> probably makes more sense.

I'm not quite sure what you mean by consitency here. This structure
has 5 other variables with two words: vpu_src_fmt, src_fmt,
vpu_dst_fmt, dst_fmt and dst_bufs. codec_current would be going
against the consistency of that structure.

> IMO using the natural English order is fine for temporary variables, but
>  less so for variables used in common parts like structures. This allows
> seeing "_" as a logical hierarchical delimiter that automatically makes
> us end up with consistent prefixes that can easily be grepped for and
> derived.
> 
> But that's just my 2 cents, it's really not a big deal, especially in
> this case!
> 
> >  	struct v4l2_ctrl_handler hdl;
> >  	struct v4l2_ctrl *ctrls[SUNXI_CEDRUS_CTRL_MAX];
> > @@ -107,6 +108,14 @@ struct sunxi_cedrus_buffer *vb2_to_cedrus_buffer(const struct vb2_buffer *p)
> >  	return vb2_v4l2_to_cedrus_buffer(to_vb2_v4l2_buffer(p));
> >  }
> >  
> > +struct sunxi_cedrus_dec_ops {
> > +	void (*setup)(struct sunxi_cedrus_ctx *ctx,
> > +		      struct sunxi_cedrus_run *run);
> > +	void (*trigger)(struct sunxi_cedrus_ctx *ctx);
> 
> By the way, are we sure that these functions won't ever fail?
> I think this is the case for MPEG2 (there is virtually nothing to check
> for errors) but perhaps it's different for H264.

It won't fail either, and if we need to change it somewhere down the
line, it's quite easy to do.

Maxime

-- 
Maxime Ripard, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
https://bootlin.com

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