On Tue, 5 Dec 2023 02:43:30 +0100 Marek Vasut <marex@xxxxxxx> wrote: > On 12/4/23 12:29, Jonathan Cameron wrote: > > On Mon, 27 Nov 2023 22:26:53 +0100 > > Marek Vasut <marex@xxxxxxx> wrote: > > > >> The ISL76682 is very basic ALS which only supports ALS or IR mode > >> in four ranges, 1k/4k/16k/64k LUX. There is no IRQ support or any > >> other fancy functionality. > >> > >> Reviewed-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx> > >> Reviewed-by: Matti Vaittinen <mazziesaccount@xxxxxxxxx> > >> Signed-off-by: Marek Vasut <marex@xxxxxxx> > > > > There is a additional question on what scale means for > > an IR channel. There aren't any well defined units (as it depends > > on the sensitivity curve) so in general we avoid providing scale > > for intensity readings. > > > > The datasheet has a vague go at working around this problem by > > using counts relative to IR measurement in daylight which would > > measure 210 LUX. (via faking that with a 850nm green led??) > > > > That's far from a standard.. > > > > We do have precedence of scale applied to intensity channels > > so I guess the ship has sailed. > > > > Perhaps we should just add an explicit not to the ABI docs > > to cover that changing the scale in these sensors will result > > in the counts changing, but multiplying raw by scale isn't going > > to give any sensible units. > > > > So probably not a thing to fix in this series, but to address > > separately. > > Is something like this what you have in mind ? Yes, something along those lines. We could add more detail on why but perhaps that would just confuse things more than just stating it is the case. > > diff --git a/Documentation/ABI/testing/sysfs-bus-iio > b/Documentation/ABI/testing/sysfs-bus-iio > index 0eadc08c3a139..584607f560d02 100644 > --- a/Documentation/ABI/testing/sysfs-bus-iio > +++ b/Documentation/ABI/testing/sysfs-bus-iio > @@ -618,7 +618,9 @@ KernelVersion: 2.6.35 > Contact: linux-iio@xxxxxxxxxxxxxxx > Description: > If a discrete set of scale values is available, they > - are listed in this attribute. > + are listed in this attribute. Unlike illumination, > + multiplying intensity by intensity_scale does not > + yield value with any standardized unit . > > What: /sys/bus/iio/devices/iio:deviceX/out_voltageY_hardwaregain > What: /sys/bus/iio/devices/iio:deviceX/in_intensity_hardwaregain >
