linux-kernel - Re: [PATCH v2 2/3] iio: light: Add support for AL3000a illuminance sensor

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Message-ID: <20250217142433.12183a17@jic23-huawei>
Date: Mon, 17 Feb 2025 14:24:33 +0000
From: Jonathan Cameron <jic23@...nel.org>
To: Svyatoslav Ryhel <clamor95@...il.com>
Cc: Lars-Peter Clausen <lars@...afoo.de>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Thierry Reding <thierry.reding@...il.com>, Jonathan
 Hunter <jonathanh@...dia.com>, Javier Carrasco
 <javier.carrasco.cruz@...il.com>, Matti Vaittinen
 <mazziesaccount@...il.com>, Andy Shevchenko
 <andriy.shevchenko@...ux.intel.com>, Emil Gedenryd
 <emil.gedenryd@...s.com>, Arthur Becker <arthur.becker@...tec.com>, Mudit
 Sharma <muditsharma.info@...il.com>, Per-Daniel Olsson
 <perdaniel.olsson@...s.com>, Subhajit Ghosh
 <subhajit.ghosh@...aklogic.com>, Ivan Orlov <ivan.orlov0322@...il.com>,
 David Heidelberg <david@...t.cz>, linux-iio@...r.kernel.org,
 devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-tegra@...r.kernel.org
Subject: Re: [PATCH v2 2/3] iio: light: Add support for AL3000a illuminance
 sensor


Hi,

> > > +static int al3000a_read_raw(struct iio_dev *indio_dev,
> > > +                         struct iio_chan_spec const *chan, int *val,
> > > +                         int *val2, long mask)
> > > +{
> > > +     struct al3000a_data *data = iio_priv(indio_dev);
> > > +     int ret, gain;
> > > +
> > > +     switch (mask) {
> > > +     case IIO_CHAN_INFO_RAW:
> > > +             ret = regmap_read(data->regmap, AL3000A_REG_DATA, &gain);
> > > +             if (ret < 0)
> > > +                     return ret;
> > > +
> > > +             *val = lux_table[gain & AL3000A_GAIN_MASK];  
> >
> > I may have misinterpreted the other thread.  IS this value in lux?
> > If it is make this channel IIO_CHAN_INFO_PROCESSED instead.
> >  
> 
> This is actually a really good hint, I will check if this works out
> and if yes, then definitely will use it. Thank you.

From your other reply it seems we have no idea of the correct scaling.
If that is the case, then channel type should be IIO_INTENSITY as
I assume we also have no idea if the light sensitivity curve is
matched to that required for illuminance (which approximates the
sensitivity of the human eye).  Various datasheets provide completely
garbage conversion formulas btw so even if we have data this can
be problematic. One recent sensor was using a green filter and
saying illuminance in lux was 1.2 * green which was assuming their
own definition of white light.

Jonathan