Pavel Machek wrote: > Exactly; if your hw can be damaged by software, it was misdesigned. > > Is the paragraph #1 really neccessary? > It provides a little background on the subject matter. I don't think it's mandatory, but I don't see the harm in keeping it. I think it improves the document overall from an editorial perspective, however. >> +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? >> +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. > 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. b.g. -- Bill Gatliff Embedded systems training and consulting http://billgatliff.com bgat@xxxxxxxxxxxxxxx -- 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
