[2/2] media: i2c: adv7604: Fix range of hue control

The ADV7604, ADV7611 and ADV7612 software manuals different the CP_HUE
value differently:

- For ADV7604 and ADV7611, the hue is specified as an unsigned 8-bit
  value, and calculated as

  (CP_HUE[7:0] * 180) / 256 - 90

  with the range set to [-90°, 90°]. Additionally, the values 0x00, 0x0f
  and 0xff are documented as corresponding to -90°, 0° and 90°
  respectively.

- For ADV7612, the hue is specified as a signed 8-bit value in the range
  [0°, 360°[ without any formula. Additionally, the value 0x00 is
  documented as corresponding to 0°.

The ADV7604 and ADV7611 documentation is clearly wrong as the example
values don't correspond to the formula. Furthermore, the [-90°, 90°]
range seems incorrect as it would cover only half of the hue space.

The ADV7612 documentation is better, although the range should likely be
[-180°, 180°[ if the value is signed. Given that the values wrap around,
this makes no difference in practice.

The hue values have been verified on ADV7612 to follow the
documentation. There is a high chance they do as well on ADV7604 and
ADV7611.

In any case, all software manuals document the register as 8-bit, so the
current range of the V4L2 hue control [0, 128] is not correct. Expand it
to cover the full 8-bit space, using unsigned values to avoid breaking
any application that may rely on 128 being a valid value.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
---
 drivers/media/i2c/adv7604.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

On 10/02/2023 23:56, Laurent Pinchart wrote:
> The ADV7604, ADV7611 and ADV7612 software manuals different the CP_HUE
> value differently:
> 
> - For ADV7604 and ADV7611, the hue is specified as an unsigned 8-bit
>   value, and calculated as
> 
>   (CP_HUE[7:0] * 180) / 256 - 90
> 
>   with the range set to [-90°, 90°]. Additionally, the values 0x00, 0x0f
>   and 0xff are documented as corresponding to -90°, 0° and 90°
>   respectively.
> 
> - For ADV7612, the hue is specified as a signed 8-bit value in the range
>   [0°, 360°[ without any formula. Additionally, the value 0x00 is
>   documented as corresponding to 0°.
> 
> The ADV7604 and ADV7611 documentation is clearly wrong as the example
> values don't correspond to the formula. Furthermore, the [-90°, 90°]
> range seems incorrect as it would cover only half of the hue space.
> 
> The ADV7612 documentation is better, although the range should likely be
> [-180°, 180°[ if the value is signed. Given that the values wrap around,
> this makes no difference in practice.
> 
> The hue values have been verified on ADV7612 to follow the
> documentation. There is a high chance they do as well on ADV7604 and
> ADV7611.
> 
> In any case, all software manuals document the register as 8-bit, so the
> current range of the V4L2 hue control [0, 128] is not correct. Expand it
> to cover the full 8-bit space, using unsigned values to avoid breaking
> any application that may rely on 128 being a valid value.
> 
> Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
> ---
>  drivers/media/i2c/adv7604.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/media/i2c/adv7604.c b/drivers/media/i2c/adv7604.c
> index 3af0e67f9edb..3d0898c4175e 100644
> --- a/drivers/media/i2c/adv7604.c
> +++ b/drivers/media/i2c/adv7604.c
> @@ -3548,7 +3548,7 @@ static int adv76xx_probe(struct i2c_client *client)
>  	v4l2_ctrl_new_std(hdl, &adv76xx_ctrl_ops,
>  			V4L2_CID_SATURATION, 0, 255, 1, 128);
>  	v4l2_ctrl_new_std(hdl, &adv76xx_ctrl_ops,
> -			V4L2_CID_HUE, 0, 128, 1, 0);
> +			V4L2_CID_HUE, 0, 255, 1, 0);
>  	ctrl = v4l2_ctrl_new_std_menu(hdl, &adv76xx_ctrl_ops,
>  			V4L2_CID_DV_RX_IT_CONTENT_TYPE, V4L2_DV_IT_CONTENT_TYPE_NO_ITC,
>  			0, V4L2_DV_IT_CONTENT_TYPE_NO_ITC);

Tested with the adv7604.

Reviewed-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Tested-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>

Thank you for looking at this!

	Hans