linux-kernel - Re: [PATCH] iio: acpi: Add ACPI0008 Ambient Light Sensor

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Date:	Thu, 30 Apr 2015 11:44:36 +0200
From:	Marek Vasut <marex@...x.de>
To:	Gabriele Mazzotta <gabriele.mzt@...il.com>
Cc:	jic23@...nel.org, knaack.h@....de, lars@...afoo.de,
	pmeerw@...erw.net, marxin.liska@...il.com, rui.zhang@...el.com,
	linux-kernel@...r.kernel.org, linux-iio@...r.kernel.org
Subject: Re: [PATCH] iio: acpi: Add ACPI0008 Ambient Light Sensor

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
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