[libcamera-devel] [PATCH 2/2] media: imx258: Limit the max analogue gain to 480

[Umang Jain]

The range for analog gain mentioned in the datasheet is [0, 480].
The real gain formula mentioned in the datasheet is:

	Gain = 512 / (512 – X)

Hence, values larger than 511 clearly makes no sense. The gain
register field is also documented to be of 9-bits in the datasheet.

Certainly, it is enough to infer that, the kernel driver currently
advertises an arbitrary analog gain max. Fix it by rectifying the
value as per the data sheet i.e. 480.

Signed-off-by: Umang Jain <umang.jain at ideasonboard.com>
---
 drivers/media/i2c/imx258.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/media/i2c/imx258.c b/drivers/media/i2c/imx258.c
index 4e695096e5d0..81cdf37216ca 100644
--- a/drivers/media/i2c/imx258.c
+++ b/drivers/media/i2c/imx258.c
@@ -47,7 +47,7 @@
 /* Analog gain control */
 #define IMX258_REG_ANALOG_GAIN		0x0204
 #define IMX258_ANA_GAIN_MIN		0
-#define IMX258_ANA_GAIN_MAX		0x1fff
+#define IMX258_ANA_GAIN_MAX		480
 #define IMX258_ANA_GAIN_STEP		1
 #define IMX258_ANA_GAIN_DEFAULT		0x0
 
-- 
2.31.1