Hi Hans,
On Tue, Aug 28, 2018 at 12:03:25PM +0200, Hans Verkuil wrote:
> Hi Philippe,
>
> On 28/08/18 09:55, Philippe De Muyter wrote:
> > add max_interval and step_interval to struct
> > v4l2_subdev_frame_interval_enum.
>
> Yeah, I never understood why this wasn't supported when this API was designed.
> Clearly an oversight.
>
> >
> > When filled correctly by the sensor driver, those fields must be
> > used as follows by the intermediate level :
> >
> > struct v4l2_frmivalenum *fival;
> > struct v4l2_subdev_frame_interval_enum fie;
> >
> > if (fie.max_interval.numerator == 0) {
> > fival->type = V4L2_FRMIVAL_TYPE_DISCRETE;
> > fival->discrete = fie.interval;
> > } else if (fie.step_interval.numerator == 0) {
> > fival->type = V4L2_FRMIVAL_TYPE_CONTINUOUS;
> > fival->stepwise.min = fie.interval;
> > fival->stepwise.max = fie.max_interval;
> > } else {
> > fival->type = V4L2_FRMIVAL_TYPE_STEPWISE;
> > fival->stepwise.min = fie.interval;
> > fival->stepwise.max = fie.max_interval;
> > fival->stepwise.step = fie.step_interval;
> > }
>
> This is a bit too magical for my tastes. I'd add a type field:
>
> #define V4L2_SUBDEV_FRMIVAL_TYPE_DISCRETE 0
> #define V4L2_SUBDEV_FRMIVAL_TYPE_CONTINUOUS 1
> #define V4L2_SUBDEV_FRMIVAL_TYPE_STEPWISE 2
Like that ?
struct v4l2_subdev_frame_interval_enum {
__u32 index;
__u32 pad;
__u32 code;
__u32 width;
__u32 height;
struct v4l2_fract interval;
__u32 which;
__u32 type;
struct v4l2_fract max_interval;
struct v4l2_fract step_interval;
__u32 reserved[3];
};
>
> Older applications that do not know about the type field will just
> see a single discrete interval containing the minimum interval.
> I guess that's OK as they will keep working.
That's actually what also happens with the above implementation, because
max_interval.numerator and step_interval.numerator were previously
reserved and thus 0, and if this code is moved to a helper function,
that does not matter if it's a little bit magical :).
Both implementations are equal to me, but the proposed one uses less
space from the 'reserved' field.
>
> While at it: it would be really nice if you can also add stepwise
> support to VIDIOC_SUBDEV_ENUM_FRAME_SIZE. I think the only thing
> you need to do there is to add two new fields: step_width and step_height.
> If 0, then that just means a step size of 1.
I'll look at that if I find enough interest and test opportunity for it,
but those things are unrelated except that they are missing :)
>
> Add some helper functions to translate between v4l2_subdev_frame_size/interval_enum
> and v4l2_frmsize/ivalenum and this becomes much cleaner.
OK
>
> Regards,
>
> Hans
>
> >
> > Signed-off-by: Philippe De Muyter <phdm@xxxxxxxxx>
> > ---
> > .../uapi/v4l/vidioc-subdev-enum-frame-interval.rst | 39 +++++++++++++++++++++-
> > include/uapi/linux/v4l2-subdev.h | 4 ++-
> > 2 files changed, 41 insertions(+), 2 deletions(-)
> >
> > diff --git a/Documentation/media/uapi/v4l/vidioc-subdev-enum-frame-interval.rst b/Documentation/media/uapi/v4l/vidioc-subdev-enum-frame-interval.rst
> > index 1bfe386..acc516e 100644
> > --- a/Documentation/media/uapi/v4l/vidioc-subdev-enum-frame-interval.rst
> > +++ b/Documentation/media/uapi/v4l/vidioc-subdev-enum-frame-interval.rst
> > @@ -51,6 +51,37 @@ EINVAL error code if one of the input fields is invalid. All frame
> > intervals are enumerable by beginning at index zero and incrementing by
> > one until ``EINVAL`` is returned.
> >
> > +If the sub-device can work only at the fixed set of frame intervals,
> > +driver must enumerate them with increasing indexes, by only filling
> > +the ``interval`` field. If the sub-device can work with a continuous
> > +range of frame intervals, driver must only return success for index 0
> > +and fill ``interval`` with the minimum interval, ``max_interval`` with
> > +the maximum interval, and ``step_interval`` with 0 or the step between
> > +the possible intervals.
> > +
> > +Callers are expected to use the returned information as follows :
> > +
> > +.. code-block:: c
> > +
> > + struct v4l2_frmivalenum * fival;
> > + struct v4l2_subdev_frame_interval_enum fie;
> > +
> > + if (fie.max_interval.numerator == 0) {
> > + fival->type = V4L2_FRMIVAL_TYPE_DISCRETE;
> > + fival->discrete = fie.interval;
> > + } else if (fie.step_interval.numerator == 0) {
> > + fival->type = V4L2_FRMIVAL_TYPE_CONTINUOUS;
> > + fival->stepwise.min = fie.interval;
> > + fival->stepwise.max = fie.max_interval;
> > + } else {
> > + fival->type = V4L2_FRMIVAL_TYPE_STEPWISE;
> > + fival->stepwise.min = fie.interval;
> > + fival->stepwise.max = fie.max_interval;
> > + fival->stepwise.step = fie.step_interval;
> > + }
> > +
> > +.. code-block:: c
> > +
> > Available frame intervals may depend on the current 'try' formats at
> > other pads of the sub-device, as well as on the current active links.
> > See :ref:`VIDIOC_SUBDEV_G_FMT` for more
> > @@ -92,8 +123,14 @@ multiple pads of the same sub-device is not defined.
> > - ``which``
> > - Frame intervals to be enumerated, from enum
> > :ref:`v4l2_subdev_format_whence <v4l2-subdev-format-whence>`.
> > + * - struct :c:type:`v4l2_fract`
> > + - ``max_interval``
> > + - Maximum period, in seconds, between consecutive video frames, or 0.
> > + * - struct :c:type:`v4l2_fract`
> > + - ``step_interval``
> > + - Frame interval step size, in seconds, or 0.
> > * - __u32
> > - - ``reserved``\ [8]
> > + - ``reserved``\ [4]
> > - Reserved for future extensions. Applications and drivers must set
> > the array to zero.
> >
> > diff --git a/include/uapi/linux/v4l2-subdev.h b/include/uapi/linux/v4l2-subdev.h
> > index 03970ce..c944644 100644
> > --- a/include/uapi/linux/v4l2-subdev.h
> > +++ b/include/uapi/linux/v4l2-subdev.h
> > @@ -128,7 +128,9 @@ struct v4l2_subdev_frame_interval_enum {
> > __u32 height;
> > struct v4l2_fract interval;
> > __u32 which;
> > - __u32 reserved[8];
> > + struct v4l2_fract max_interval;
> > + struct v4l2_fract step_interval;
> > + __u32 reserved[4];
> > };
> >
> > /**
> >
--
Philippe De Muyter +32 2 6101532 Macq SA rue de l'Aeronef 2 B-1140 Bruxelles
