linux-kernel - Re: [PATCH 4/4] media: imx-media-capture: add frame sizes/interval enumeration

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Date:   Mon, 20 Mar 2017 09:05:25 +0000
From:   Russell King - ARM Linux <linux@...linux.org.uk>
To:     Philippe De Muyter <phdm@...q.eu>
Cc:     Steve Longerbeam <steve_longerbeam@...tor.com>,
        Steve Longerbeam <slongerbeam@...il.com>,
        sakari.ailus@...ux.intel.com, hverkuil@...all.nl,
        linux-media@...r.kernel.org, kernel@...gutronix.de,
        mchehab@...nel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, p.zabel@...gutronix.de
Subject: Re: [PATCH 4/4] media: imx-media-capture: add frame sizes/interval
 enumeration

On Mon, Mar 20, 2017 at 09:55:12AM +0100, Philippe De Muyter wrote:
> Hi Russel,
> 
> On Sun, Mar 19, 2017 at 10:49:08AM +0000, Russell King wrote:
> > Add support for enumerating frame sizes and frame intervals from the
> > first subdev via the V4L2 interfaces.
> > 
> > Signed-off-by: Russell King <rmk+kernel@...linux.org.uk>
> > ---
> >  drivers/staging/media/imx/imx-media-capture.c | 62 +++++++++++++++++++++++++++
> >  1 file changed, 62 insertions(+)
> > 
> ...
> > +static int capture_enum_frameintervals(struct file *file, void *fh,
> > +				       struct v4l2_frmivalenum *fival)
> > +{
> > +	struct capture_priv *priv = video_drvdata(file);
> > +	const struct imx_media_pixfmt *cc;
> > +	struct v4l2_subdev_frame_interval_enum fie = {
> > +		.index = fival->index,
> > +		.pad = priv->src_sd_pad,
> > +		.width = fival->width,
> > +		.height = fival->height,
> > +		.which = V4L2_SUBDEV_FORMAT_ACTIVE,
> > +	};
> > +	int ret;
> > +
> > +	cc = imx_media_find_format(fival->pixel_format, CS_SEL_ANY, true);
> > +	if (!cc)
> > +		return -EINVAL;
> > +
> > +	fie.code = cc->codes[0];
> > +
> > +	ret = v4l2_subdev_call(priv->src_sd, pad, enum_frame_interval, NULL, &fie);
> > +	if (ret)
> > +		return ret;
> > +
> > +	fival->type = V4L2_FRMIVAL_TYPE_DISCRETE;
> > +	fival->discrete = fie.interval;
> 
> For some parallel sensors (mine is a E2V ev76c560) "any" frame interval is possible,
> and hence type should be V4L2_FRMIVAL_TYPE_CONTINUOUS.

For my sensor, any frame interval is also possible, but that isn't the
point here.

/dev/video* only talks to the CSI source pad, not it's sink pad.  The
sink pad gets configured with the sensor frame rate via the media
controller API.  /dev/video* itself has no control over the sensor
frame rate.

The media controller stuff completely changes the way the established
/dev/video* functionality works - the ability to select arbitary frame
sizes and frame rates supported by the ultimate sensor is gone.  All
that needs to be setup through the media controller pipeline, one
subdev at a time.

-- 
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