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From: Marek Vasut <marex@denx.de>
To: Gabriele Mazzotta <gabriele.mzt@gmail.com>
Subject: Re: [PATCH] iio: acpi: Add ACPI0008 Ambient Light Sensor
Date: Thu, 30 Apr 2015 11:44:36 +0200
Cc: jic23@kernel.org,
 knaack.h@gmx.de,
 lars@metafoo.de,
 pmeerw@pmeerw.net,
 marxin.liska@gmail.com,
 rui.zhang@intel.com,
 linux-kernel@vger.kernel.org,
 linux-iio@vger.kernel.org
References: <1430306845-7117-1-git-send-email-gabriele.mzt@gmail.com> <201504291633.18558.marex@denx.de> <1724765.vloEsYdA9s@xps13>
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On Wednesday, April 29, 2015 at 05:36:32 PM, Gabriele Mazzotta wrote:
[...]
> > > I'm sorry, I've just noticed that I haven't changed the value of
> > > realbits in acpi_als_channels. This makes me wonder what would be the
> > > proper value, given that this is a generic driver and all the
> > > information I have are those in the ACPI specification (which states
> > > what I reported here above).
> > > 
> > > Should I just set realbits to 32?
> > 
> > I believe the ALS reports only 16bit signel value, no ?
> > My observation with a strong coherent light source is that
> > the saturated sensor reported 0xffff .
> 
> Probably it's the same for me. I couldn't get to the point where
> ALI reports 0xffff, just really close, I will have to try with some
> stronger lights. However, looking at my ACPI table, I can see that
> the value returned by _ALI is just the composition of two 8 bits
> variables put side by side, so yes, I can say that even on my system
> it's a 16bit value.

What kind of hardware are you testing this on ?

> The problem here is that I'm not sure we can assume this as true in
> general since the ACPI specification doesn't say anything.

Maybe someone more knowledgable can speak up.

Best regards,
Marek Vasut