Re: [PATCH v3 15/17] media: i2c: os05b10: fix negative hblank calculation

[Jai Luthra]

Quoting Tarang Raval (2026-07-19 01:39:06)
> hblank is computed as "mode->hts - mode->width", but both are u32.
> For every mode hts < width (e.g. 1744 vs 2592 for 2592x1944), so the
> subtraction wraps in unsigned 32-bit arithmetic instead of going
> negative. That wrapped value ends up in the control's s64 min/max,
> which v4l2-compliance flags as out of range:
> 
>     fail: v4l2-test-controls.cpp(413): returned control value out of range
>     fail: v4l2-test-controls.cpp(476): invalid control 009e0902
> 
> and v4l2-ctl shows:
> 
>     horizontal_blanking 0x009e0902 (int): min=4294966448 max=4294966448
>     step=1 default=4294966448 value=-848 flags=read-only, has-min-max
> 
> The same bug exists in os05b10_init_controls(), which sets the
> control's default before os05b10_set_framing_limits() runs.
> 
> Fix both sites by casting to a signed type before subtracting, so the
> real (possibly negative) value is computed directly.
> 

While the framework accepts negative blankings, IMHO they physically don't
make much sense.

Many sensors scale their HTS register by some constant factor, so increment
of 1 in HTS does not mean 1 pixel on a line, but 4 or 8 or n pixels.
This also affects the internal "pixel rate" for framerate calculation.

Please look at imx283, imx678 etc.

Thanks,
    Jai

> Fixes: 3aa9296a23ec4 ("media: i2c: add os05b10 image sensor driver")
> Signed-off-by: Tarang Raval <tarang.raval@xxxxxxxxxxxxxxxxx>