Re: [PATCH v7 7/7] media: uvcvideo: document UVC v1.5 ROI

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Yunke,

Thank you for the patch.

On Tue, Jun 28, 2022 at 04:57:05PM +0900, Yunke Cao wrote:
> Added documentation of V4L2_CID_UVC_REGION_OF_INTEREST_RECT and
> V4L2_CID_UVC_REGION_OF_INTEREST_AUTO.
> 
> Signed-off-by: Yunke Cao <yunkec@google.com>
> ---
>  .../userspace-api/media/drivers/uvcvideo.rst  | 61 +++++++++++++++++++
>  1 file changed, 61 insertions(+)
> 
> diff --git a/Documentation/userspace-api/media/drivers/uvcvideo.rst b/Documentation/userspace-api/media/drivers/uvcvideo.rst
> index a290f9fadae9..ee4c182aa274 100644
> --- a/Documentation/userspace-api/media/drivers/uvcvideo.rst
> +++ b/Documentation/userspace-api/media/drivers/uvcvideo.rst
> @@ -181,6 +181,7 @@ Argument: struct uvc_xu_control_mapping
>  	UVC_CTRL_DATA_TYPE_BOOLEAN	Boolean
>  	UVC_CTRL_DATA_TYPE_ENUM		Enumeration
>  	UVC_CTRL_DATA_TYPE_BITMASK	Bitmask
> +	UVC_CTRL_DATA_TYPE_RECT		Rectangular area
>  
>  
>  UVCIOC_CTRL_QUERY - Query a UVC XU control
> @@ -255,3 +256,63 @@ Argument: struct uvc_xu_control_query
>  	__u8	query		Request code to send to the device
>  	__u16	size		Control data size (in bytes)
>  	__u8	*data		Control value
> +

You can add a second blank line here, as above the "Extension Unit (XU)
support" title.

> +Private V4L2 controls

"Driver-specific V4L2 controls" would be better, those controls are not
private.

> +---------------------
> +
> +A few UVC specific V4L2 control IDs are listed below.

s/UVC specific/UVC-specific/

But I'd write

The uvcvideo driver implements the following UVC-specific controls:

> +
> +``V4L2_CID_UVC_REGION_OF_INTEREST_RECT (struct)``
> +	This control determines the region of interest (ROI). ROI is an

s/is an/is a/

> +	rectangular area represented by a struct :c:type:`v4l2_rect`. The
> +	rectangle is in global sensor coordinates and pixel units. It is
> +	independent of the field of view, not impacted by any cropping or
> +	scaling.
> +
> +	Use ``V4L2_CTRL_WHICH_MIN_VAL`` and ``V4L2_CTRL_WHICH_MAX_VAL`` to query
> +	the range of rectangle sizes. For example, a device can have a minimum
> +	ROI rectangle of 1x1@0x0 and a maximum of 640x480@0x0.

Minimum and maximum values for rectangles are ill-defined. Are the top
and left coordinates always 0 ? If so that should be documented.

> +
> +	Setting a ROI allows the camera to optimize the capture for the region.
> +	The value of ``V4L2_CID_REGION_OF_INTEREST_AUTO`` control determines
> +	the detailed behavior.
> +
> +
> +``V4L2_CID_UVC_REGION_OF_INTEREST_AUTO (bitmask)``
> +	This determines which, if any, on board features should track to the
> +	Region of Interest specified by the current value of
> +	``V4L2_CID_UVD__REGION_OF_INTEREST_RECT``.
> +
> +	Max value is a mask indicating all supported Auto
> +	Controls.

No need to wrap this line.

> +
> +.. flat-table::
> +    :header-rows:  0
> +    :stub-columns: 0
> +
> +    * - ``V4L2_REGION_OF_INTEREST_AUTO_EXPOSURE``

s/V4L2/V4L2_UVC/

Same below.

> +      - Setting this to true enables automatic exposure time for the specified

s/exposure time/exposure/ (as it can also include gain)

> +	region.

It's not that it enables automatic exposure for the specified region, is
that it causes the automatic exposure to track the region of interest
instead of the whole image. Same below.

> +    * - ``V4L2_REGION_OF_INTEREST_AUTO_IRIS``
> +      - Setting this to true enables automatic iris aperture for the specified
> +	region.
> +    * - ``V4L2_REGION_OF_INTEREST_AUTO_WHITE_BALANCE``
> +      - Setting this to true enables automatic white balance adjustment for the
> +	specified region.
> +    * - ``V4L2_REGION_OF_INTEREST_AUTO_FOCUS``
> +      - Setting this to true enables automatic focus adjustment for the
> +	specified region.
> +    * - ``V4L2_REGION_OF_INTEREST_AUTO_FACE_DETECT``
> +      - Setting this to true enables automatic face detection for the
> +	specified region.
> +    * - ``V4L2_REGION_OF_INTEREST_AUTO_DETECT_AND_TRACK``
> +      - Setting this to true enables automatic face detection and tracking. The
> +	current value of ``V4L2_CID_REGION_OF_INTEREST_RECT`` may be updated by
> +	the driver.
> +    * - ``V4L2_REGION_OF_INTEREST_AUTO_IMAGE_STABILIZATION``
> +      - Setting this to true enables automatic image stabilization. The
> +	current value of ``V4L2_CID_REGION_OF_INTEREST_RECT`` may be updated by
> +	the driver.

How so ?

> +    * - ``V4L2_REGION_OF_INTEREST_AUTO_HIGHER_QUALITY``
> +      - Setting this to true enables automatically capture the specified region
> +	with higher quality if possible.

Could you please clarify this one ? I'm not sure to understand what it
means.

-- 
Regards,

Laurent Pinchart