> >> +pwm_free() -- Marks a PWM channel as no longer in use. The PWM device > >> +is stopped before it is released by the API. > >> > > > > free is normally used for something else. Rename to open/close? > ... or request/release? Works for me. > >> +pwm_start(), pwm_stop() -- Turns the PWM signal on and off. Except > >> +where stated otherwise by a driver author, signals are stopped at the > >> +end of the current period, at which time the output is set to its > >> +inactive state. > >> > > > > What does it mean to stop a signal? What is the difference between 0% > > duty cycle and stop() ? > > > > Depends on the hardware. For a true PWM peripheral, a 0% duty cycle > might still have the base peripheral clock for the device running. > Whereas a pwm_stop() signal could be used to turn off the clock to the > peripheral. If it is just powersaving... I'd do it automatically when 0% duty is selected...? Or is that infeasible due to latency...? > > Is polarity realy required? Can't driver just replace duty with > > 100%-duty > > Actually, yes in some cases. Users can always do the 100%-duty math, > but some hardware asserts a specific output state when you stop the > peripheral that's potentially different from 0% duty. Also, some > hardware begins the PWM cycle with the output high, while others do with > the output low. It isn't necessarily the case that the user cares, but > I was thinking that having the API allow for different polarity might > prevent some applications having to optionally do the %duty vs. > 100-%duty conversion themselves. Ok, ok, but this should go into the docs. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html -- To unsubscribe from this list: send the line "unsubscribe linux-embedded" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
