linux-kernel - Re: [PATCH] iio: light: acpi-als: Report data as processed rather than raw

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Message-ID: <CABFtUbRT2bWsUCn6sCxytZDoAV5hC9rojpJUwXJrt2EEXyCSVA@mail.gmail.com>
Date:	Tue, 12 Jan 2016 16:27:33 +0100
From:	Gabriele Mazzotta <gabriele.mzt@...il.com>
To:	Jonathan Cameron <jic23@...nel.org>
Cc:	Marek Vasut <marex@...x.de>, Hartmut Knaack <knaack.h@....de>,
	Lars-Peter Clausen <lars@...afoo.de>,
	Peter Meerwald-Stadler <pmeerw@...erw.net>,
	Martin Liška <marxin.liska@...il.com>,
	linux-iio@...r.kernel.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] iio: light: acpi-als: Report data as processed rather
 than raw

2016-01-11 20:18 GMT+01:00 Jonathan Cameron <jic23@...nel.org>:
> On 09/01/16 17:27, Marek Vasut wrote:
>> On Saturday, January 09, 2016 at 05:31:24 PM, Jonathan Cameron wrote:
>>> On 07/01/16 15:21, Gabriele Mazzotta wrote:
>>>> As per the ACPI specification (Revision 5.0) [1], the data coming
>>>> from the sensor represent the ambient light illuminance reading
>>>> expressed in lux. Use IIO_CHAN_INFO_PROCESSED instead of
>>>> IIO_CHAN_INFO_RAW to signify that the data are pre-processed.
>>>>
>>>> [1] http://www.acpi.info/DOWNLOADS/ACPIspec50.pdf
>>>>
>>>> Signed-off-by: Gabriele Mazzotta <gabriele.mzt@...il.com>
>>>
>>> Hm. Whilst it's a fix in a sense, the original didn't really 'break'
>>> the ABI so I worry a little that this change may break others.
>>> Irritating as it is, perhaps we should keep the _RAW and add _PROCESSED
>>> (which will then be exactly the same value).
>>> We'll also then need a comment in the code, that leaving the _RAW
>>> elements was for ABI compatibility.
>>>
>>> What do others think?
>>
>> I'm not an IIO guru, but this does sound sensible. Do you know if any userland
>> code which actually uses the ACPI ALS already ?
> It's more than likely as Gnome at least supports using them to control screen
> brightness.  Hopefully that code is able to cope with the correct ABI though as
> well as the old one.  Anyhow, we seem to have a reasonable consensus.

I looked into this and Gnome uses iio-proxy-sensor to handle iio
devices. As of now it, only looks for in_illuminance_input, so it
currently doesn't work with acpi-als. I've also found a bug report [1]
of an acpi-als user stating the same.

[1] https://github.com/hadess/iio-sensor-proxy/issues/46

> Gabriele, are you happy to do a version of the patch with the _RAW version
> left along side your _PROCESSED version and a comment saying that it is for
> compatibility only?
>
> Jonathan
>>
>> Best regards,
>> Marek Vasut
>> --
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>