Re: [PATCH v3 19/23] media: atmel: atmel-isc-base: clamp wb gain coefficients

Jacopo Mondi
2022-01-12T09:03:10Z

Hi Eugen

On Mon, Dec 13, 2021 at 03:49:36PM +0200, Eugen Hristev wrote:
> White balance computed gains can overflow above the 13 bits hardware
> coefficient that can be used, in some specific scenarios like a subexposure
> from the sensor when the image is mostly black.
> In this case the computed gain has to be clamped to the maximum value
> allowed by the hardware.
>
> Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>
> ---
> drivers/media/platform/atmel/atmel-isc-base.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/drivers/media/platform/atmel/atmel-isc-base.c b/drivers/media/platform/atmel/atmel-isc-base.c
> index f1f1019f9d82..31c8e3029eee 100644
> --- a/drivers/media/platform/atmel/atmel-isc-base.c
> +++ b/drivers/media/platform/atmel/atmel-isc-base.c
> @@ -1415,6 +1415,10 @@ static void isc_wb_update(struct isc_ctrls *ctrls)
> /* multiply both gains and adjust for decimals */
> ctrls->gain[c] = s_gain[c] * gw_gain[c];
> ctrls->gain[c] >>= 9;
> +
> + /* make sure we are not out of range */
> + ctrls->gain[c] = clamp_val(ctrls->gain[c], 0, GENMASK(12, 0));

#include <linux/minmax.h>

What is the type of gain[c} ? If it's unsigned clamping with [0 is not
required. I would in that case gain[c] = min(gain[c], ...)

It's fine anyway
Reviewed-by: Jacopo Mondi <jacopo+renesas@jmondi.org>

Thanks
j

> +
> v4l2_dbg(1, debug, &isc->v4l2_dev,
> "isc wb: component %d, final gain %u\n",
> c, ctrls->gain[c]);
> --
> 2.25.1
>