PWM.clear_channel followed by init_channel fails

[mlv]

I need to change the subcycle_time_us of a channel after it's been initialized, but it seems to be impossible.

First, I tried PWM.clear_channel(chan) before PWM.init_channel(chan, subcycle_time_us=new_stu), but it gave an error that the channel was already initialized. Next, I tried a more draconian cleanup() call (I don't want to touch other channels, and this would mean initializing all of them which I really don't want to do, but even that didn't work.

It looks like the problem is the virtbase pointer in the channel structure. It's used throughout pwm.c to indicate whether the channel has been initialized. init_channel checks if it's set, and assumes it's initialized if it is set. But clear_channel doesn't clear it (and neither does shutdown (called by cleanup)). As there's no way to clear virtbase, there's no way to change the subcycle_time_us of a channel.