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

[Sergei Shtylyov <sergei.shtylyov@gmail.com>]

Hello!

On 2/11/23 1:56 AM, Laurent Pinchart wrote:

> The ADV7604, ADV7611 and ADV7612 software manuals different the CP_HUE

   s/different/document/?

> 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>
[...]

MBR, Sergey