diff mbox series

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

Message ID 20211213134940.324266-20-eugen.hristev@microchip.com
State Accepted
Commit 3f050110617de71c6bc65867fc56bdb30ee07f38
Headers show
Series [v3,01/23] MAINTAINERS: add microchip csi2dc | expand

Commit Message

Eugen Hristev Dec. 13, 2021, 1:49 p.m. UTC
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(+)

Comments

Jacopo Mondi Jan. 12, 2022, 9:04 a.m. UTC | #1
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
>
diff mbox series

Patch

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