linux-kernel - Re: [PATCH 2/2] iio: light: Add support for Capella cm36686 and cm36672p sensors

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Message-ID: <0b001503-5882-446c-a0df-642a9f75e7e3@baylibre.com>
Date: Tue, 3 Feb 2026 10:36:49 -0600
From: David Lechner <dlechner@...libre.com>
To: Erikas Bitovtas <xerikasxx@...il.com>, Jonathan Cameron
 <jic23@...nel.org>, Nuno Sá <nuno.sa@...log.com>,
 Andy Shevchenko <andy@...nel.org>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Kevin Tsai <ktsai@...ellamicro.com>
Cc: linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org, ~postmarketos/upstreaming@...ts.sr.ht,
 phone-devel@...r.kernel.org
Subject: Re: [PATCH 2/2] iio: light: Add support for Capella cm36686 and
 cm36672p sensors

On 2/3/26 9:41 AM, Erikas Bitovtas wrote:
>> Pro tip: when you reply, trim out the not relevant parts like this.
> 
> Noted.
>> We could start with hard-coding the als_trans_ratio in this driver for the
>> scale (and write comments explaining where it came from and what we know
>> and don't know). Then at least we would have a scale. And if anyone needs
>> something more accurate and reverse-engineers it we could fix it up later
>> with a DT property or something like that.
>>
> 
> In arch/arm/boot/dts/qcom/libra/common-proximity.dtsi Xiaomi sets this property
> to 16, and they set integration time in their driver to 160ms. Maybe
> als_trans_ratio has something to do with integration time? 

I assume you have the hardware and can do a test to confirm this. :-)

> In that case, we can
> calculate the scale from a formula, like this:
> scale = cm36686_als_it_times[index][1] / 10000 * 40000
> val = scale / 1000000
> val2 = scale % 1000000
> This would allow us to preserve lux value when changing integration time.