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

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Message-ID: <56940003.2040209@kernel.org>
Date:	Mon, 11 Jan 2016 19:18:27 +0000
From:	Jonathan Cameron <jic23@...nel.org>
To:	Marek Vasut <marex@...x.de>
Cc:	Gabriele Mazzotta <gabriele.mzt@...il.com>, knaack.h@....de,
	lars@...afoo.de, pmeerw@...erw.net, marxin.liska@...il.com,
	linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] iio: light: acpi-als: Report data as processed rather
 than raw

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. 
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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