| Message ID | 20220614083614.240641-2-benjamin.gaignard@collabora.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Move HEVC stateless controls out of staging | expand |
Hi Benjamin, On 6/14/22 10:35, Benjamin Gaignard wrote: > From: Hans Verkuil <hverkuil-cisco@xs4all.nl> > > Add a new flag that indicates that this control is a dynamically sized > array. Also document this flag. > > Currently dynamically sized arrays are limited to one dimensional arrays, > but that might change in the future if there is a need for it. > > The initial use-case of dynamic arrays are stateless codecs. A frame > can be divided in many slices, so you want to provide an array containing > slice information for each slice. Typically the number of slices is small, > but the standard allow for hundreds or thousands of slices. Dynamic arrays > are a good solution since sizing the array for the worst case would waste > substantial amounts of memory. > > Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl> > --- > .../userspace-api/media/v4l/vidioc-queryctrl.rst | 8 ++++++++ > include/uapi/linux/videodev2.h | 1 + > 2 files changed, 9 insertions(+) > > diff --git a/Documentation/userspace-api/media/v4l/vidioc-queryctrl.rst b/Documentation/userspace-api/media/v4l/vidioc-queryctrl.rst > index 88f630252d98..a20dfa2a933b 100644 > --- a/Documentation/userspace-api/media/v4l/vidioc-queryctrl.rst > +++ b/Documentation/userspace-api/media/v4l/vidioc-queryctrl.rst > @@ -625,6 +625,14 @@ See also the examples in :ref:`control`. > ``V4L2_CTRL_FLAG_GRABBED`` flag when buffers are allocated or > streaming is in progress since most drivers do not support changing > the format in that case. > + * - ``V4L2_CTRL_FLAG_DYNAMIC_ARRAY`` > + - 0x0800 > + - This control is a dynamically sized 1-dimensional array. It > + behaves the same as a regular array, except that the number > + of elements as reported by the ``elems`` field is between 1 and > + ``dims[0]``. So setting the control with a differently sized > + array will change the ``elems`` field when the control is > + queried afterwards. I am proposing a change to the dynamic array implementation: initially dynamic array controls start off as empty arrays (0 elements). This also allows userspace to set a dynamic array control to an empty array. It probably would also make sense to add a min_dyn_elems to set the minimum allowed number of elements for a dynamic array. This would most likely be either 0 or 1. In the context of this HEVC series, does it help to allow empty dynamic arrays? For V4L2_CID_STATELESS_HEVC_ENTRY_POINT_OFFSETS in particular it looks like it would make sense since I think (correct me if I am wrong) there can be 0 entry point offsets. So with empty arrays supported would the field num_entry_point_offsets still be needed? If you want to test, then let me know and I mail a very simple patch adding support for empty arrays (not yet min_dyn_elems, though). Regards, Hans > > Return Value > ============ > diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h > index 5311ac4fde35..9018aa984db3 100644 > --- a/include/uapi/linux/videodev2.h > +++ b/include/uapi/linux/videodev2.h > @@ -1890,6 +1890,7 @@ struct v4l2_querymenu { > #define V4L2_CTRL_FLAG_HAS_PAYLOAD 0x0100 > #define V4L2_CTRL_FLAG_EXECUTE_ON_WRITE 0x0200 > #define V4L2_CTRL_FLAG_MODIFY_LAYOUT 0x0400 > +#define V4L2_CTRL_FLAG_DYNAMIC_ARRAY 0x0800 > > /* Query flags, to be ORed with the control ID */ > #define V4L2_CTRL_FLAG_NEXT_CTRL 0x80000000
Le 15/06/2022 à 11:33, Hans Verkuil a écrit : > Hi Benjamin, > > On 6/14/22 10:35, Benjamin Gaignard wrote: >> From: Hans Verkuil <hverkuil-cisco@xs4all.nl> >> >> Add a new flag that indicates that this control is a dynamically sized >> array. Also document this flag. >> >> Currently dynamically sized arrays are limited to one dimensional arrays, >> but that might change in the future if there is a need for it. >> >> The initial use-case of dynamic arrays are stateless codecs. A frame >> can be divided in many slices, so you want to provide an array containing >> slice information for each slice. Typically the number of slices is small, >> but the standard allow for hundreds or thousands of slices. Dynamic arrays >> are a good solution since sizing the array for the worst case would waste >> substantial amounts of memory. >> >> Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl> >> --- >> .../userspace-api/media/v4l/vidioc-queryctrl.rst | 8 ++++++++ >> include/uapi/linux/videodev2.h | 1 + >> 2 files changed, 9 insertions(+) >> >> diff --git a/Documentation/userspace-api/media/v4l/vidioc-queryctrl.rst b/Documentation/userspace-api/media/v4l/vidioc-queryctrl.rst >> index 88f630252d98..a20dfa2a933b 100644 >> --- a/Documentation/userspace-api/media/v4l/vidioc-queryctrl.rst >> +++ b/Documentation/userspace-api/media/v4l/vidioc-queryctrl.rst >> @@ -625,6 +625,14 @@ See also the examples in :ref:`control`. >> ``V4L2_CTRL_FLAG_GRABBED`` flag when buffers are allocated or >> streaming is in progress since most drivers do not support changing >> the format in that case. >> + * - ``V4L2_CTRL_FLAG_DYNAMIC_ARRAY`` >> + - 0x0800 >> + - This control is a dynamically sized 1-dimensional array. It >> + behaves the same as a regular array, except that the number >> + of elements as reported by the ``elems`` field is between 1 and >> + ``dims[0]``. So setting the control with a differently sized >> + array will change the ``elems`` field when the control is >> + queried afterwards. > I am proposing a change to the dynamic array implementation: initially > dynamic array controls start off as empty arrays (0 elements). This also > allows userspace to set a dynamic array control to an empty array. > > It probably would also make sense to add a min_dyn_elems to set the minimum > allowed number of elements for a dynamic array. This would most likely be > either 0 or 1. > > In the context of this HEVC series, does it help to allow empty dynamic arrays? > > For V4L2_CID_STATELESS_HEVC_ENTRY_POINT_OFFSETS in particular it looks like > it would make sense since I think (correct me if I am wrong) there can be 0 > entry point offsets. So with empty arrays supported would the field > num_entry_point_offsets still be needed? yes it possible to have 0 entry point offsets in bitstream but in this case I think the stack won't use V4L2_CID_STATELESS_HEVC_ENTRY_POINT_OFFSETS because it have not data to send. I have introduce num_entry_point_offsets field because most of the drivers only need this information and not the full offsets array so I think it is needed. For now none of the drivers use V4L2_CID_STATELESS_HEVC_ENTRY_POINT_OFFSETS control, it is here to be future proof. Regards, Benjamin > > If you want to test, then let me know and I mail a very simple patch adding > support for empty arrays (not yet min_dyn_elems, though). > > Regards, > > Hans > >> >> Return Value >> ============ >> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h >> index 5311ac4fde35..9018aa984db3 100644 >> --- a/include/uapi/linux/videodev2.h >> +++ b/include/uapi/linux/videodev2.h >> @@ -1890,6 +1890,7 @@ struct v4l2_querymenu { >> #define V4L2_CTRL_FLAG_HAS_PAYLOAD 0x0100 >> #define V4L2_CTRL_FLAG_EXECUTE_ON_WRITE 0x0200 >> #define V4L2_CTRL_FLAG_MODIFY_LAYOUT 0x0400 >> +#define V4L2_CTRL_FLAG_DYNAMIC_ARRAY 0x0800 >> >> /* Query flags, to be ORed with the control ID */ >> #define V4L2_CTRL_FLAG_NEXT_CTRL 0x80000000
Hi >Hi Benjamin, > >On 6/14/22 10:35, Benjamin Gaignard wrote: >> From: Hans Verkuil <hverkuil-cisco@xs4all.nl> >> >> Add a new flag that indicates that this control is a dynamically sized >> array. Also document this flag. >> >> Currently dynamically sized arrays are limited to one dimensional arrays, >> but that might change in the future if there is a need for it. >> >> The initial use-case of dynamic arrays are stateless codecs. A frame >> can be divided in many slices, so you want to provide an array containing >> slice information for each slice. Typically the number of slices is small, >> but the standard allow for hundreds or thousands of slices. Dynamic arrays >> are a good solution since sizing the array for the worst case would waste >> substantial amounts of memory. >> >> Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl> >> --- >> .../userspace-api/media/v4l/vidioc-queryctrl.rst | 8 ++++++++ >> include/uapi/linux/videodev2.h | 1 + >> 2 files changed, 9 insertions(+) >> >> diff --git a/Documentation/userspace-api/media/v4l/vidioc-queryctrl.rst b/Documentation/userspace-api/media/v4l/vidioc-queryctrl.rst >> index 88f630252d98..a20dfa2a933b 100644 >> --- a/Documentation/userspace-api/media/v4l/vidioc-queryctrl.rst >> +++ b/Documentation/userspace-api/media/v4l/vidioc-queryctrl.rst >> @@ -625,6 +625,14 @@ See also the examples in :ref:`control`. >> ``V4L2_CTRL_FLAG_GRABBED`` flag when buffers are allocated or >> streaming is in progress since most drivers do not support changing >> the format in that case. >> + * - ``V4L2_CTRL_FLAG_DYNAMIC_ARRAY`` >> + - 0x0800 >> + - This control is a dynamically sized 1-dimensional array. It >> + behaves the same as a regular array, except that the number >> + of elements as reported by the ``elems`` field is between 1 and >> + ``dims[0]``. So setting the control with a differently sized >> + array will change the ``elems`` field when the control is >> + queried afterwards. > >I am proposing a change to the dynamic array implementation: initially >dynamic array controls start off as empty arrays (0 elements). This also >allows userspace to set a dynamic array control to an empty array. > >It probably would also make sense to add a min_dyn_elems to set the minimum >allowed number of elements for a dynamic array. This would most likely be >either 0 or 1. > >In the context of this HEVC series, does it help to allow empty dynamic arrays? I'd assumed that the control simply wouldn't be set if empty, but yes I think it makes sense to allow empty otherwise there would be no way of clearing the control if it was ever set? >For V4L2_CID_STATELESS_HEVC_ENTRY_POINT_OFFSETS in particular it looks like >it would make sense since I think (correct me if I am wrong) there can be 0 >entry point offsets. So with empty arrays supported would the field >num_entry_point_offsets still be needed? Yes - assuming that the entry_point array is still 1D (I think that was what was decided) then still you need it to work out which entry points belong to which slice. Regards JC >If you want to test, then let me know and I mail a very simple patch adding >support for empty arrays (not yet min_dyn_elems, though). > >Regards, > > Hans > >> >> Return Value >> ============ >> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h >> index 5311ac4fde35..9018aa984db3 100644 >> --- a/include/uapi/linux/videodev2.h >> +++ b/include/uapi/linux/videodev2.h >> @@ -1890,6 +1890,7 @@ struct v4l2_querymenu { >> #define V4L2_CTRL_FLAG_HAS_PAYLOAD 0x0100 >> #define V4L2_CTRL_FLAG_EXECUTE_ON_WRITE 0x0200 >> #define V4L2_CTRL_FLAG_MODIFY_LAYOUT 0x0400 >> +#define V4L2_CTRL_FLAG_DYNAMIC_ARRAY 0x0800 >> >> /* Query flags, to be ORed with the control ID */ >> #define V4L2_CTRL_FLAG_NEXT_CTRL 0x80000000
diff --git a/Documentation/userspace-api/media/v4l/vidioc-queryctrl.rst b/Documentation/userspace-api/media/v4l/vidioc-queryctrl.rst index 88f630252d98..a20dfa2a933b 100644 --- a/Documentation/userspace-api/media/v4l/vidioc-queryctrl.rst +++ b/Documentation/userspace-api/media/v4l/vidioc-queryctrl.rst @@ -625,6 +625,14 @@ See also the examples in :ref:`control`. ``V4L2_CTRL_FLAG_GRABBED`` flag when buffers are allocated or streaming is in progress since most drivers do not support changing the format in that case. + * - ``V4L2_CTRL_FLAG_DYNAMIC_ARRAY`` + - 0x0800 + - This control is a dynamically sized 1-dimensional array. It + behaves the same as a regular array, except that the number + of elements as reported by the ``elems`` field is between 1 and + ``dims[0]``. So setting the control with a differently sized + array will change the ``elems`` field when the control is + queried afterwards. Return Value ============ diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h index 5311ac4fde35..9018aa984db3 100644 --- a/include/uapi/linux/videodev2.h +++ b/include/uapi/linux/videodev2.h @@ -1890,6 +1890,7 @@ struct v4l2_querymenu { #define V4L2_CTRL_FLAG_HAS_PAYLOAD 0x0100 #define V4L2_CTRL_FLAG_EXECUTE_ON_WRITE 0x0200 #define V4L2_CTRL_FLAG_MODIFY_LAYOUT 0x0400 +#define V4L2_CTRL_FLAG_DYNAMIC_ARRAY 0x0800 /* Query flags, to be ORed with the control ID */ #define V4L2_CTRL_FLAG_NEXT_CTRL 0x80000000