Hi all, I'm currently working on a linux kernel driver for a new sensor design. It's a special kind of light sensor that measures the reflection of emitted light. I'm trying to fit this type of sensor into the IIO subsystem but I hit some issues. Question 1: The sensor measures the absorbance[1] of a material. It's the negative logarithmic quotient of the received and emitted light. It's a unit-less value. As far as I can see there is currently no predefined IIO type in the kernel for this. I have search the list [2], but nothing matches. Do I overlook something or what channel type should I use for this sensor measurement value? Question 2: The sensor effectively returns a float value of the measurement. I grepped trough the existing IIO drivers, but there seems only one driver that deals with float values. The sps30 driver[3] gets a float from the device, but converts it to a integer value before passing it to the IIO subsystem. I know that it's possible to provide a 'scale' attribute per channel to userspace[4], which can be a float point number. So effectively the result of a measurement can be a float-point value after it's computed in userspace. Are floats really not supported as channel values? What is the recommend approach to deal with these measurement values? Question 3: Is there another kernel subsystem/UAPI that fits this type of sensor better? (My guess would be: No, IIO is the correct subsystem.) Thanks a lot for answering my question. Kind regards, Stefan [1]: https://en.wikipedia.org/wiki/Absorbance [2]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/include/uapi/linux/iio/types.h#n14 [3]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/iio/chemical/sps30.c#n39 [4]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/iio/dummy/iio_simple_dummy.c#n122
