linux-kernel - Re: [PATCH v7 4/5] iio: light: ROHM BU27034 Ambient Light Sensor

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Message-ID: <c14e3897-0186-681e-45b6-d079111c893e@fi.rohmeurope.com>
Date:   Wed, 12 Apr 2023 11:55:26 +0000
From:   "Vaittinen, Matti" <Matti.Vaittinen@...rohmeurope.com>
To:     Matti Vaittinen <mazziesaccount@...il.com>,
        Jonathan Cameron <jic23@...nel.org>
CC:     Lars-Peter Clausen <lars@...afoo.de>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Paul Gazzillo <paul@...zz.com>,
        Dmitry Osipenko <dmitry.osipenko@...labora.com>,
        Shreeya Patel <shreeya.patel@...labora.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>
Subject: Re: [PATCH v7 4/5] iio: light: ROHM BU27034 Ambient Light Sensor

On 4/10/23 13:38, Matti Vaittinen wrote:
> On 4/8/23 14:21, Jonathan Cameron wrote:
>> On Fri, 31 Mar 2023 15:41:58 +0300
>> Matti Vaittinen <mazziesaccount@...il.com> wrote:
>>
>>> ROHM BU27034 is an ambient light sensor with 3 channels and 3 photo 
>>> diodes
>>> capable of detecting a very wide range of illuminance. Typical 
>>> application
>>> is adjusting LCD and backlight power of TVs and mobile phones.
>>>
>>> Add initial  support for the ROHM BU27034 ambient light sensor.
>>>
>>> NOTE:
>>>     - Driver exposes 4 channels. One IIO_LIGHT channel providing the
>>>       calculated lux values based on measured data from diodes #0 and
>>>       #1. In addition, 3 IIO_INTENSITY channels are emitting the raw
>>>       register data from all diodes for more intense user-space
>>>       computations.
>>>     - Sensor has GAIN values that can be adjusted from 1x to 4096x.
>>>     - Sensor has adjustible measurement times of 5, 55, 100, 200 and
>>>       400 mS. Driver does not support 5 mS which has special
>>>       limitations.
>>>     - Driver exposes standard 'scale' adjustment which is
>>>       implemented by:
>>>         1) Trying to adjust only the GAIN
>>>         2) If GAIN adjustment alone can't provide requested
>>>            scale, adjusting both the time and the gain is
>>>            attempted.
>>>     - Driver exposes writable INT_TIME property that can be used
>>>       for adjusting the measurement time. Time adjustment will also
>>>       cause the driver to try to adjust the GAIN so that the
>>>       overall scale is kept as close to the original as possible.
>>>
>>> Signed-off-by: Matti Vaittinen <mazziesaccount@...il.com>

As I wrote in the other (sysfs) mail - this driver version is buggy as 
it handles INT_TIMEs in micro seconds. The correct unit would be seconds.

I'll send an incremental fix to this and the gts-helpers on top of the 
iio/togreg (hopefully soon).

Yours,
	-- Matti

-- 
Matti Vaittinen
Linux kernel developer at ROHM Semiconductors
Oulu Finland

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