Correctness of acpi-als channel mask

Correctness of acpi-als channel mask

[Gabriele Mazzotta]

Hi,

I have a question regarding the acpi-als driver.

Currently acpi-als uses IIO_CHAN_INFO_RAW to report the data coming
from the sensor. However, as per the ACPI specification [1] (section
9.2.2), these values represent the ambient light illuminance expressed
in lux. Wouldn't IIO_CHAN_INFO_PROCESSED be more appropriate in this
case as the data are in theory pre-processed by the firmware of the
platform?

[1] http://www.acpi.info/DOWNLOADS/ACPIspec50.pdf

Regards,
Gabriele

Re: Correctness of acpi-als channel mask

[Jonathan Cameron]

On 17/12/15 20:32, Gabriele Mazzotta wrote:
> Hi,
> 
> I have a question regarding the acpi-als driver.
> 
> Currently acpi-als uses IIO_CHAN_INFO_RAW to report the data coming
> from the sensor. However, as per the ACPI specification [1] (section
> 9.2.2), these values represent the ambient light illuminance expressed
> in lux. Wouldn't IIO_CHAN_INFO_PROCESSED be more appropriate in this
> case as the data are in theory pre-processed by the firmware of the
> platform?
Looks like it to me as well.  Cc'd Marek and Martin.
> 
> [1] http://www.acpi.info/DOWNLOADS/ACPIspec50.pdf
> 
> Regards,
> Gabriele
> --
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> 

Re: Correctness of acpi-als channel mask

[Marek Vasut]

On Saturday, December 19, 2015 at 05:09:33 PM, Jonathan Cameron wrote:
> On 17/12/15 20:32, Gabriele Mazzotta wrote:
> > Hi,
> > 
> > I have a question regarding the acpi-als driver.
> > 
> > Currently acpi-als uses IIO_CHAN_INFO_RAW to report the data coming
> > from the sensor. However, as per the ACPI specification [1] (section
> > 9.2.2), these values represent the ambient light illuminance expressed
> > in lux. Wouldn't IIO_CHAN_INFO_PROCESSED be more appropriate in this
> > case as the data are in theory pre-processed by the firmware of the
> > platform?
> 
> Looks like it to me as well.  Cc'd Marek and Martin.

Gotta say, I haven't looked at ACPI for a while now. My impression is that these 
data are RAW and the system software can adjust them based on the values in _ALR
table. The result of that would be _PROCESSED I think. But I might be entirely 
wrong.

> > [1] http://www.acpi.info/DOWNLOADS/ACPIspec50.pdf
> > 
> > Regards,
> > Gabriele
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-iio" in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html

Best regards,
Marek Vasut

Re: Correctness of acpi-als channel mask

[Marek Vasut]

On Monday, December 21, 2015 at 11:08:55 AM, Gabriele Mazzotta wrote:
> 2015-12-21 0:33 GMT+01:00 Marek Vasut <marex@denx.de>:
> > On Saturday, December 19, 2015 at 05:09:33 PM, Jonathan Cameron wrote:
> >> On 17/12/15 20:32, Gabriele Mazzotta wrote:
> >> > Hi,
> >> > 
> >> > I have a question regarding the acpi-als driver.
> >> > 
> >> > Currently acpi-als uses IIO_CHAN_INFO_RAW to report the data coming
> >> > from the sensor. However, as per the ACPI specification [1] (section
> >> > 9.2.2), these values represent the ambient light illuminance expressed
> >> > in lux. Wouldn't IIO_CHAN_INFO_PROCESSED be more appropriate in this
> >> > case as the data are in theory pre-processed by the firmware of the
> >> > platform?
> >> 
> >> Looks like it to me as well.  Cc'd Marek and Martin.
> > 
> > Gotta say, I haven't looked at ACPI for a while now. My impression is
> > that these data are RAW and the system software can adjust them based on
> > the values in _ALR table. The result of that would be _PROCESSED I
> > think. But I might be entirely wrong.
> 
> I'm not sure of this. _ALR returns an ambient light illuminance to
> display luminance mapping that suggests how to adjust the screen
> backlight. There are then _ALC and _ALT which report the ambient light
> color chromaticity and the ambient light color temperature respectively.

ALC and ALT are optional I believe (at least I recall my crappy old hardware
on which I first implemented this didn't have them at all). Thanks for 
clarifying what the ALR means, I never really understood how that was supposed 
to work in the first place .

> So I don't think there are adjustments we can perform.

If you think _PROCESSED is more appropriate, I will not oppose it. At this 
point, you are the bigger expert on ALS :)

> >> > [1] http://www.acpi.info/DOWNLOADS/ACPIspec50.pdf
> >> > 
> >> > Regards,
> >> > Gabriele
> >> > --
> >> > To unsubscribe from this list: send the line "unsubscribe linux-iio"
> >> > in the body of a message to majordomo@vger.kernel.org
> >> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> > 
> > Best regards,
> > Marek Vasut

Best regards,
Marek Vasut