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

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Date:   Mon, 20 Mar 2017 17:29:07 +0100
From:   Philipp Zabel <p.zabel@...gutronix.de>
To:     Russell King - ARM Linux <linux@...linux.org.uk>
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, 2017-03-20 at 15:43 +0000, Russell King - ARM Linux wrote:
> On Mon, Mar 20, 2017 at 02:20:16PM +0100, Philipp Zabel wrote:
> > To set and read colorimetry information:
> > https://patchwork.linuxtv.org/patch/39350/
> 
> Thanks, I've applied all four of your patches, but there's a side effect
> from that.  Old media-ctl (modified by me):
> 
> - entity 53: imx219 0-0010 (2 pads, 2 links)
>              type V4L2 subdev subtype Unknown flags 0
>              device node name /dev/v4l-subdev9
>         pad0: Source
>                 [fmt:SRGGB8/816x616 field:none
>                  frame_interval:1/25]
>                 -> "imx6-mipi-csi2":0 [ENABLED]
>         pad1: Sink
>                 [fmt:SRGGB10/3280x2464 field:none
>                  crop.bounds:(0,0)/3280x2464
>                  crop:(0,0)/3264x2464
>                  compose.bounds:(0,0)/3264x2464
>                  compose:(0,0)/816x616]
>                 <- "imx219 pixel 0-0010":0 [ENABLED,IMMUTABLE]
> 
> New media-ctl:
> 
> - entity 53: imx219 0-0010 (2 pads, 2 links)
>              type V4L2 subdev subtype Unknown flags 0
>              device node name /dev/v4l-subdev9
>         pad0: Source
>                 [fmt:SRGGB8_1X8/816x616@...5 field:none colorspace:srgb xfer:srgb]
>                 -> "imx6-mipi-csi2":0 [ENABLED]
>         pad1: Sink
>                 <- "imx219 pixel 0-0010":0 [ENABLED,IMMUTABLE]
> 
> It looks like we successfully retrieve the frame interval for pad 0
> and print it, but when we try to retrieve the frame interval for pad 1,
> we get EINVAL (because that's what I'm returning, but I'm wondering if
> that's the correct thing to do...) and that prevents _all_ format
> information being output.

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

> 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.

>  
>  	if (format.field)
>  		printf(" field:%s", v4l2_subdev_field_to_string(format.field));
> 
> 

regards
Philipp