Re: [RFC 0/6] Proposal for a Generic PWM Device API

[Bill Gatliff <bgat@billgatliff.com>]

Mike Frysinger wrote:
> if you'd seriously play with a Blackfin board, i think we can arrange that

I'd seriously *love* to play with one, but I'm pretty strapped for time for
another couple of months.  The only purpose it would serve near-term would be to
prove out the input capabilities of a device that I probably wouldn't have time
to write a driver for.  :(

> while true, hardware that can support PWM as both input/output would
> suffer from two frameworks.  if there's ambiguity in behavior (using
> "get" in an output mode), then we can just stick it in the
> documentation and move on.  the GPIO framework already has this
> behavior (set a pin to output and then try and read the data) and i
> dont recall it ever being an issue there.

Good point.  I think I'm sold on the idea now.

We'd need a PWM_CONFIG_<something> to tell the hardware to switch to
"measurement mode" if such a mode is supported (suggestions for <something>
welcomed).  The config function would return an error if the measurement mode
wasn't supported by the device.  PWM_CONFIG_INPUT and PWM_CONFIG_OUTPUT, perhaps?

In output mode, the pwm_get_*() methods would return the driven values if the
device didn't support a (simultaneous) measurement mode, or cached values if the
device's configuration registers were write-only.  In measurement mode, they'd
return the measured values.

I think this'll work.



b.g.
-- 
Bill Gatliff
bgat@billgatliff.com