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.

quoted

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.

quoted

 
 	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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