Re: [PATCHv2 4/6] videodev2.h: add V4L2_CTRL_FLAG_REQUIRES_REQUESTS

[Hans Verkuil <hverkuil-cisco@xs4all.nl>]

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.

Regards,

	Hans

> 
> Signed-off-by: Hans Verkuil <hverkuil-cisco@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
>