linux-kernel - Re: [PATCH v5 00/39] i.MX Media Driver

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Message-ID: <20170320163547.GP21222@n2100.armlinux.org.uk>
Date:   Mon, 20 Mar 2017 16:35:47 +0000
From:   Russell King - ARM Linux <linux@...linux.org.uk>
To:     Philipp Zabel <p.zabel@...gutronix.de>
Cc:     Steve Longerbeam <steve_longerbeam@...tor.com>,
        Steve Longerbeam <slongerbeam@...il.com>, robh+dt@...nel.org,
        mark.rutland@....com, shawnguo@...nel.org, kernel@...gutronix.de,
        fabio.estevam@....com, mchehab@...nel.org, hverkuil@...all.nl,
        nick@...anahar.org, markus.heiser@...marIT.de,
        laurent.pinchart+renesas@...asonboard.com, bparrot@...com,
        geert@...ux-m68k.org, arnd@...db.de, sudipm.mukherjee@...il.com,
        minghsiu.tsai@...iatek.com, tiffany.lin@...iatek.com,
        jean-christophe.trotin@...com, horms+renesas@...ge.net.au,
        niklas.soderlund+renesas@...natech.se, robert.jarzmik@...e.fr,
        songjun.wu@...rochip.com, andrew-ct.chen@...iatek.com,
        gregkh@...uxfoundation.org, shuah@...nel.org,
        sakari.ailus@...ux.intel.com, pavel@....cz,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-media@...r.kernel.org,
        devel@...verdev.osuosl.org
Subject: Re: [PATCH v5 00/39] i.MX Media Driver

On Mon, Mar 20, 2017 at 05:29:07PM +0100, Philipp Zabel wrote:
> According to the documentation [1], you are doing the right thing:
> 
>     The struct v4l2_subdev_frame_interval pad references a non-existing
>     pad, or the pad doesn’t support frame intervals.
> 
> But v4l2_subdev_call returns -ENOIOCTLCMD if the g_frame_interval op is
> not implemented at all, which is turned into -ENOTTY by video_usercopy.
> 
> [1] https://linuxtv.org/downloads/v4l-dvb-apis/uapi/v4l/vidioc-subdev-g-frame-interval.html#return-value

Thanks for confirming.

> > Maybe something like the following would be a better idea?
> > 
> >  utils/media-ctl/media-ctl.c | 10 +++++-----
> >  1 file changed, 5 insertions(+), 5 deletions(-)
> > 
> > diff --git a/utils/media-ctl/media-ctl.c b/utils/media-ctl/media-ctl.c
> > index f61963a..a50a559 100644
> > --- a/utils/media-ctl/media-ctl.c
> > +++ b/utils/media-ctl/media-ctl.c
> > @@ -81,22 +81,22 @@ static void v4l2_subdev_print_format(struct media_entity *entity,
> >  	struct v4l2_mbus_framefmt format;
> >  	struct v4l2_fract interval = { 0, 0 };
> >  	struct v4l2_rect rect;
> > -	int ret;
> > +	int ret, err_fi;
> >  
> >  	ret = v4l2_subdev_get_format(entity, &format, pad, which);
> >  	if (ret != 0)
> >  		return;
> >  
> > -	ret = v4l2_subdev_get_frame_interval(entity, &interval, pad);
> > -	if (ret != 0 && ret != -ENOTTY)
> > -		return;
> > +	err_fi = v4l2_subdev_get_frame_interval(entity, &interval, pad);
> 
> Not supporting frame intervals doesn't warrant a visible error message,
> I think -EINVAL should also be ignored above, if the spec is to be
> believed.
> 
> >  
> >  	printf("\t\t[fmt:%s/%ux%u",
> >  	       v4l2_subdev_pixelcode_to_string(format.code),
> >  	       format.width, format.height);
> >  
> > -	if (interval.numerator || interval.denominator)
> > +	if (err_fi == 0 && (interval.numerator || interval.denominator))
> >  		printf("@%u/%u", interval.numerator, interval.denominator);
> > +	else if (err_fi != -ENOTTY)
> > +		printf("@<error: %s>", strerror(-err_fi));
> 
> Or here.

I don't mind which - I could change this to:

	else if (err_fi != -ENOTTY && err_fi != -EINVAL)

Or an alternative would be to print an error (ignoring ENOTTY and EINVAL)
to stderr at the "v4l2_subdev_get_frame_interval" callsite and continue
on (ensuring that interval is zeroed).

-- 
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