Re: [PATCH v4 4/9] media: Documentation: dw100: Add user documentation for the DW100 driver

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On 28/03/2022 16:13, Xavier Roumegue wrote:
> Add user documentation for the DW100 driver.
> 
> Signed-off-by: Xavier Roumegue <xavier.roumegue@xxxxxxxxxxx>
> ---
>  .../userspace-api/media/drivers/dw100.rst     | 23 +++++++++++++++++++
>  .../userspace-api/media/drivers/index.rst     |  1 +
>  2 files changed, 24 insertions(+)
>  create mode 100644 Documentation/userspace-api/media/drivers/dw100.rst
> 
> diff --git a/Documentation/userspace-api/media/drivers/dw100.rst b/Documentation/userspace-api/media/drivers/dw100.rst
> new file mode 100644
> index 000000000000..4cd55c75628e
> --- /dev/null
> +++ b/Documentation/userspace-api/media/drivers/dw100.rst
> @@ -0,0 +1,23 @@
> +.. SPDX-License-Identifier: GPL-2.0
> +
> +DW100 dewarp driver
> +===========================
> +
> +The Vivante DW100 Dewarp Processor IP core found on i.MX8MP SoC applies a
> +programmable geometrical transformation on input image to correct distorsion
> +introduced by lenses.
> +
> +The transformation function is exposed by the hardware as a grid map with 16x16
> +pixel macroblocks indexed using X, Y vertex coordinates. Each x, y coordinate
> +register uses 16 bits to record the coordinate address in UQ12.4 fixed point

'UQ12.4' is a mostly TI notation it seems: https://en.wikipedia.org/wiki/Q_(number_format)

I would replace this with: ...in an unsigned 12.4 fixed point format

And in the control documentation this can be documented more precisely (I'll comment on
that patch).

Regards,

	Hans

> +format.
> +
> +The dewarping map can be set from application through a dedicated v4l2 control.
> +If not set or invalid, the driver computes an identity map prior to start the
> +processing engine. The map is evaluated as invalid if the array size does not
> +match the expected size inherited from the destination image resolution.
> +
> +More details on the DW100 hardware operations can be found in
> +*chapter 13.15 DeWarp* of IMX8MP_ reference manuel.
> +
> +.. _IMX8MP: https://www.nxp.com/webapp/Download?colCode=IMX8MPRM
> diff --git a/Documentation/userspace-api/media/drivers/index.rst b/Documentation/userspace-api/media/drivers/index.rst
> index 12e3c512d718..8826777321b0 100644
> --- a/Documentation/userspace-api/media/drivers/index.rst
> +++ b/Documentation/userspace-api/media/drivers/index.rst
> @@ -33,6 +33,7 @@ For more details see the file COPYING in the source distribution of Linux.
>  
>  	ccs
>  	cx2341x-uapi
> +	dw100
>          hantro
>  	imx-uapi
>  	max2175




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