linux-kernel - Re: [PATCH] iio: light: acpi-als: Add a tuning parameter interface.

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Message-ID: <CAFqH_513e24aOZ8NJ+m0WtzKmf-n3R8FwwApFGWCdgoQbJRdNA@mail.gmail.com>
Date:   Tue, 6 Sep 2016 18:48:03 +0200
From:   Enric Balletbo Serra <eballetbo@...il.com>
To:     Lars-Peter Clausen <lars@...afoo.de>
Cc:     Enric Balletbo i Serra <enric.balletbo@...labora.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-iio@...r.kernel.org, Jonathan Cameron <jic23@...nel.org>
Subject: Re: [PATCH] iio: light: acpi-als: Add a tuning parameter interface.

Hi Lars,

2016-09-06 12:31 GMT+02:00 Lars-Peter Clausen <lars@...afoo.de>:
> On 09/06/2016 12:25 PM, Enric Balletbo i Serra wrote:
>> From: Bryan Freed <bfreed@...omium.org>
>>
>> Add IIO_CHAN_INFO_CALIBSCALE to the channel to scale up or down
>> the raw measurements through the IIO framework.
>>
>> Add IIO_CHAN_INFO_PROCESSED to provide the interface to read the
>> scaled measurements through the in_illuminance_input file.
>
> What is the use-case for this, how is this interface supposed to be used?

The idea behind this is be able to do a per-device calibration. The
use case we're thinking is:

 1. Read raw measurements from sensor in controlled environment (at
30, 500 and 1000 lux)
 2. do some math to calculate the calibration value.
 3. write the value to calibscale (in_illuminance_calibscale)
 4. read the calibrated measurement (in_illuminance_input)

Regards,
  Enric