Re: [PATCH v2 2/2] iio: light: Add support for APDS9306 Light Sensor

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On 11/6/23 14:04, Subhajit Ghosh wrote:
On 6/11/23 21:43, Jonathan Cameron wrote:
On Tue, 31 Oct 2023 19:08:08 +1030
Subhajit Ghosh <subhajit.ghosh@xxxxxxxxxxxxxx> wrote:

Scale on the intensity channel is interesting...  What are the units?
There tend not to be any well defined units for intensity (as opposed
to illuminance).  There may be gain on the signal, but it won't be in untils that map directly to a scale userspace should apply.  This is one of the
rare reasons for using the HARDWARE_GAIN element of the ABI.

A tricky corner however as relationship between raw value and hardwaregain
is not tightly defined (as it can be really weird!)
Hi Jonathan,

Thank you for taking time for reviewing and clearing all my tiny doubts and
queries especially for the dt and versioning part. Much appreciated.

In the above case, should I not expose scale for the "clear" channel? Rather,
how should I expose the "clear" channel to userspace?
What is the scale?  What units to you get after applying it?
The scale is in Lux. The output after applying is Lux.

Hi Subhajit,

I am by no means an expert here but maybe you could check if the channel should be of type 'illuminance'? (To me 'Lux' sounds like an unit of illuminance rather than intensity).

Yours,
	-- Matti

--
Matti Vaittinen
Linux kernel developer at ROHM Semiconductors
Oulu Finland

~~ When things go utterly wrong vim users can always type :help! ~~




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