On 2/13/19 11:38 AM, Paul Kocialkowski wrote:
> Hi,
>
> On Mon, 2019-02-11 at 14:04 +0100, Hans Verkuil wrote:
>> On 2/11/19 11:13 AM, Hans Verkuil wrote:
>>> Indicate if a control can only be set through a request, as opposed
>>> to being set directly. This is necessary for stateless codecs where
>>> it makes no sense to set the state controls directly.
>>
>> Kwiboo on irc pointed out that this clashes with this line the in
>> Initialization
>> section of the stateless decoder API:
>>
>> "Call VIDIOC_S_EXT_CTRLS() to set all the controls (parsed headers, etc.)
>> required
>> by the OUTPUT format to enumerate the CAPTURE formats."
>>
>> So for now ignore patches 4-6: I need to think about this some more.
>>
>> My worry here is what happens when userspace is adding these controls to a
>> request and at the same time sets them directly. That may cause weird
>> side-effects.
>
> This seems to be a very legitimate concern, as nothing guarantees that
> the controls setup by v4l2_ctrl_request_setup won't be overridden
> before the driver uses them.
>
> One solution could be to mark the controls as "in use" when the request
> has new data for them, clear that in v4l2_ctrl_request_complete and
> return EBUSY when trying to set the control in between the two calls.
>
> This way, we ensure that any control set via a request will retain the
> value passed with the request, which is independent from the control
> itself (so we don't need special handling for stateless codec
> controls). It also allows setting the control outside of a request for
> enumerating formats.
>
> What do you think?
That's a good idea. I'll see if I can make that work.
Regards,
Hans
>
> Cheers,
>
> Paul
>
>> Regards,
>>
>> Hans
>>
>>> Signed-off-by: Hans Verkuil <hverkuil-ci...@xs4all.nl>
>>> ---
>>> .../media/uapi/v4l/vidioc-queryctrl.rst | 4 ++++
>>> .../media/videodev2.h.rst.exceptions | 1 +
>>> include/uapi/linux/videodev2.h | 23 ++++++++++---------
>>> 3 files changed, 17 insertions(+), 11 deletions(-)
>>>
>>> diff --git a/Documentation/media/uapi/v4l/vidioc-queryctrl.rst
>>> b/Documentation/media/uapi/v4l/vidioc-queryctrl.rst
>>> index f824162d0ea9..b08c69cedb92 100644
>>> --- a/Documentation/media/uapi/v4l/vidioc-queryctrl.rst
>>> +++ b/Documentation/media/uapi/v4l/vidioc-queryctrl.rst
>>> @@ -539,6 +539,10 @@ 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_REQUIRES_REQUESTS``
>>> + - 0x0800
>>> + - This control cannot be set directly, but only through a request
>>> + (i.e. by setting ``which`` to ``V4L2_CTRL_WHICH_REQUEST_VAL``).
>>>
>>>
>>> Return Value
>>> diff --git a/Documentation/media/videodev2.h.rst.exceptions
>>> b/Documentation/media/videodev2.h.rst.exceptions
>>> index 64d348e67df9..0caa72014dba 100644
>>> --- a/Documentation/media/videodev2.h.rst.exceptions
>>> +++ b/Documentation/media/videodev2.h.rst.exceptions
>>> @@ -351,6 +351,7 @@ replace define V4L2_CTRL_FLAG_VOLATILE control-flags
>>> replace define V4L2_CTRL_FLAG_HAS_PAYLOAD control-flags
>>> replace define V4L2_CTRL_FLAG_EXECUTE_ON_WRITE control-flags
>>> replace define V4L2_CTRL_FLAG_MODIFY_LAYOUT control-flags
>>> +replace define V4L2_CTRL_FLAG_REQUIRES_REQUESTS control-flags
>>>
>>> replace define V4L2_CTRL_FLAG_NEXT_CTRL control
>>> replace define V4L2_CTRL_FLAG_NEXT_COMPOUND control
>>> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
>>> index 7f035d44666e..a78bfdc1df97 100644
>>> --- a/include/uapi/linux/videodev2.h
>>> +++ b/include/uapi/linux/videodev2.h
>>> @@ -1736,17 +1736,18 @@ struct v4l2_querymenu {
>>> } __attribute__ ((packed));
>>>
>>> /* Control flags */
>>> -#define V4L2_CTRL_FLAG_DISABLED 0x0001
>>> -#define V4L2_CTRL_FLAG_GRABBED 0x0002
>>> -#define V4L2_CTRL_FLAG_READ_ONLY 0x0004
>>> -#define V4L2_CTRL_FLAG_UPDATE 0x0008
>>> -#define V4L2_CTRL_FLAG_INACTIVE 0x0010
>>> -#define V4L2_CTRL_FLAG_SLIDER 0x0020
>>> -#define V4L2_CTRL_FLAG_WRITE_ONLY 0x0040
>>> -#define V4L2_CTRL_FLAG_VOLATILE 0x0080
>>> -#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_DISABLED 0x0001
>>> +#define V4L2_CTRL_FLAG_GRABBED 0x0002
>>> +#define V4L2_CTRL_FLAG_READ_ONLY 0x0004
>>> +#define V4L2_CTRL_FLAG_UPDATE 0x0008
>>> +#define V4L2_CTRL_FLAG_INACTIVE 0x0010
>>> +#define V4L2_CTRL_FLAG_SLIDER 0x0020
>>> +#define V4L2_CTRL_FLAG_WRITE_ONLY 0x0040
>>> +#define V4L2_CTRL_FLAG_VOLATILE 0x0080
>>> +#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_REQUIRES_REQUESTS 0x0800
>>>
>>> /* Query flags, to be ORed with the control ID */
>>> #define V4L2_CTRL_FLAG_NEXT_CTRL 0x80000000
>>>
