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Date: Mon, 4 Dec 2023 11:29:41 +0000
From: Jonathan Cameron <jic23@kernel.org>
To: Marek Vasut <marex@denx.de>
Cc: linux-iio@vger.kernel.org, Andy Shevchenko
 <andriy.shevchenko@linux.intel.com>, Matti Vaittinen
 <mazziesaccount@gmail.com>, Alexander Stein
 <alexander.stein@ew.tq-group.com>, Andre Werner
 <andre.werner@systec-electronic.com>, Bjorn Helgaas <bhelgaas@google.com>,
 Conor Dooley <conor+dt@kernel.org>, Fabio Estevam <festevam@denx.de>,
 Guenter Roeck <linux@roeck-us.net>, Krzysztof Kozlowski
 <krzysztof.kozlowski+dt@linaro.org>, Lars-Peter Clausen <lars@metafoo.de>,
 Luca Ceresoli <luca.ceresoli@bootlin.com>, Mark Brown <broonie@kernel.org>,
 Naresh Solanki <naresh.solanki@9elements.com>, Patrick Rudolph
 <patrick.rudolph@9elements.com>, Rob Herring <robh+dt@kernel.org>, Stefan
 Windfeldt-Prytz <stefan.windfeldt-prytz@axis.com>, Vincent Tremblay
 <vincent@vtremblay.dev>, devicetree@vger.kernel.org
Subject: Re: [PATCH v6 2/2] iio: light: isl76682: Add ISL76682 driver
Message-ID: <20231204112941.770e22cb@jic23-huawei>
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On Mon, 27 Nov 2023 22:26:53 +0100
Marek Vasut <marex@denx.de> wrote:

> The ISL76682 is very basic ALS which only supports ALS or IR mode
> in four ranges, 1k/4k/16k/64k LUX. There is no IRQ support or any
> other fancy functionality.
> 
> Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> Reviewed-by: Matti Vaittinen <mazziesaccount@gmail.com>
> Signed-off-by: Marek Vasut <marex@denx.de>

There is a additional question on what scale means for
an IR channel.  There aren't any well defined units (as it depends
on the sensitivity curve) so in general we avoid providing scale
for intensity readings.

The datasheet has a vague go at working around this problem by
using counts relative to IR measurement in daylight which would
measure 210 LUX.  (via faking that with a 850nm green led??)

That's far from a standard..

We do have precedence of scale applied to intensity channels
so I guess the ship has sailed.

Perhaps we should just add an explicit not to the ABI docs
to cover that changing the scale in these sensors will result
in the counts changing, but multiplying raw by scale isn't going
to give any sensible units.

So probably not a thing to fix in this series, but to address
separately.

Jonathan