PWM: Proper channel support

[Ayush1325]

Need the pwm api to provide the number of channels supported by a pwm controller.

[rajatmohan22]

hello? If this is still open I would love to work on this

[Ayush1325]

hello? If this is still open I would love to work on this

Yup, it's open. Feel free to work on it.

Just to clarify, what is needed is some way to get the number of channels from pwm controller. Both compile time method (such as in the pwm controller dts node) or runtime (some pwm api in zephyr) is fine.

[rajatmohan22]

Hey @Ayush1325 ,

This PR adds full support for finding out how many PWM channels there are in Greybus PWM using both devicetree and runtime probing. It fixes Issue #55 and makes sure that every Greybus PWM controller sends back the right channel_num, even if the devicetree doesn't have a channels property.

[CPPavithra]

Hi @Ayush1325 ,
I would like to work on this.
I recently submitted the PWM integration test suite (basic beginning). On native_sim, the test currently passes but reports 0 channels, which highlights the need for proper channel counting support.
I can use that test harness to implement the fix and verify that the correct channel count is reported via the protocol.

I noticed there was an earlier attempt, but since it has been inactive for a few months, is it alright if I take this forward?