Re: [PATCH] imx219: selection compliance fixes

[Jacopo Mondi <jacopo@jmondi.org>]

Hi Hans,

On Thu, Jul 02, 2020 at 03:50:04PM +0200, Hans Verkuil wrote:
> The top/left crop coordinates were 0, 0 instead of 8, 8 in the
> supported_modes array. This was a mismatch with the default values,
> so this is corrected. Found with v4l2-compliance.
>
> Also add V4L2_SEL_TGT_CROP_BOUNDS support: CROP_DEFAULT and CROP_BOUNDS
> always go together. Found with v4l2-compliance.

I actually introduced this with
e6d4ef7d58aa ("media: i2c: imx219: Implement get_selection")

>
> Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
> ---
>  drivers/media/i2c/imx219.c | 17 +++++++++--------
>  1 file changed, 9 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/media/i2c/imx219.c b/drivers/media/i2c/imx219.c
> index 0a546b8e466c..935e2a258ce5 100644
> --- a/drivers/media/i2c/imx219.c
> +++ b/drivers/media/i2c/imx219.c
> @@ -473,8 +473,8 @@ static const struct imx219_mode supported_modes[] = {
>  		.width = 3280,
>  		.height = 2464,
>  		.crop = {
> -			.left = 0,
> -			.top = 0,
> +			.left = 8,
> +			.top = 8,

Mmmm, why this change ?
This values are used to report V4L2_SEL_TGT_CROP rectangle, which
according to the documentation is defined as
"Crop rectangle. Defines the cropped area."
(not a much extensive description :)

Clearly this is a faulty definition, and I know from experience how
hard is proving to define pixel array properties and in which extent
the documentation has to go:
https://lists.libcamera.org/pipermail/libcamera-devel/2020-June/009115.html

My understanding is that target should report the current crop
rectangle, defined from the rectangle retrieved with the
V4L2_SEL_TGT_CROP_DEFAULT target, which, according documentation
reports the:
"Suggested cropping rectangle that covers the “whole picture”.
This includes only active pixels and excludes other non-active pixels such
as black pixels"

The TGT_CROP_DEFAULT then reports the active pixel array portion, and
needs to be defined in respect to the TGT_NATIVE_SIZE, which reports
the dimensions of the whole pixel matrix, including non-active pixels,
optical blanks active and non-active pixels.

The TGT_CROP rectangle is hence defined from the CROP_DEFAULT one, and
if the 'whole active area' is selected, its top-left corner is placed
in position (0, 0) (what's the point of defining it in respect to an
area which cannot be read anyway ?)

Unless TGT_CROP should be defined in respect to the NATIVE_SIZE
rectangle too, but that's not specified anywhere.

Anyway, those selection targets badly apply to image sensors, are
ill-defined as the definition of active pixels, optical blank (active
and non-active) pixels is not provided anywhere, and it's not specified
anywhere what is the reference area for each of those rectangles, so I
might very well got them wrongly.

>  			.width = 3280,
>  			.height = 2464
>  		},
> @@ -489,8 +489,8 @@ static const struct imx219_mode supported_modes[] = {
>  		.width = 1920,
>  		.height = 1080,
>  		.crop = {
> -			.left = 680,
> -			.top = 692,
> +			.left = 8 + 680,
> +			.top = 8 + 692,
>  			.width = 1920,
>  			.height = 1080
>  		},
> @@ -505,8 +505,8 @@ static const struct imx219_mode supported_modes[] = {
>  		.width = 1640,
>  		.height = 1232,
>  		.crop = {
> -			.left = 0,
> -			.top = 0,
> +			.left = 8,
> +			.top = 8,
>  			.width = 3280,
>  			.height = 2464
>  		},
> @@ -521,8 +521,8 @@ static const struct imx219_mode supported_modes[] = {
>  		.width = 640,
>  		.height = 480,
>  		.crop = {
> -			.left = 1000,
> -			.top = 752,
> +			.left = 8 + 1000,
> +			.top = 8 + 752,
>  			.width = 1280,
>  			.height = 960
>  		},
> @@ -1014,6 +1014,7 @@ static int imx219_get_selection(struct v4l2_subdev *sd,
>  		return 0;
>
>  	case V4L2_SEL_TGT_CROP_DEFAULT:
> +	case V4L2_SEL_TGT_CROP_BOUNDS:

Still not getting what is the purpose of two targets if the "always
have to go together" :)

>  		sel->r.top = IMX219_PIXEL_ARRAY_TOP;
>  		sel->r.left = IMX219_PIXEL_ARRAY_LEFT;
>  		sel->r.width = IMX219_PIXEL_ARRAY_WIDTH;
> --
> 2.27.0
>