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Date: Thu, 9 May 2024 01:32:27 +0100
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Subject: Re: [PATCH v2] media: i2c: Fix imx412 exposure control
To: Dave Stevenson <dave.stevenson@raspberrypi.com>,
 Jacopo Mondi <jacopo.mondi@ideasonboard.com>
Cc: Sakari Ailus <sakari.ailus@linux.intel.com>,
 Mauro Carvalho Chehab <mchehab@kernel.org>,
 "Paul J. Murphy" <paul.j.murphy@intel.com>,
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 Daniele Alessandrelli <daniele.alessandrelli@intel.com>,
 Mauro Carvalho Chehab <mchehab+huawei@kernel.org>,
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From: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
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On 08/05/2024 17:31, Dave Stevenson wrote:
> For reference certainly imx327/290/462 which are all siblings in the
> Sony Starvis family do calculate exposure as
> exposure = 1 frame period - (SHS1 + 1) * (1H period)
> So 0 = max exposure and bigger values are shorter exposure time.

ack

> I'm not saying that the imx412 driver is right in doing this as well,
> but it seems there is a trend with the Sony Starvis family to program
> exposure in this different manner. Don't discount it as wrong for all
> drivers!

Understood. For the record the rpi imx477 driver writes the CID value 
provided by user-space.

https://github.com/raspberrypi/linux/blob/rpi-6.6.y/drivers/media/i2c/imx477.c#L1376

With an exposure multiplier we don't support upstream at the moment. So, 
I think this patch is the right fix after all.

---
bod