Re: [PATCH 0/6] Generic PWM API implementation

[David Brownell <david-b@pacbell.net>]

On Friday 13 November 2009, Grant Likely wrote:
> 		  Right now, I don't
> see a fundamental difference is between GPIO and PWM pin management.
> It is essentially the same problem, and in many cases PWM pins can
> also be used as GPIOs. 

Pin management for a given SoC is going to be relevant to setting
every signal, no matter what peripheral it's associated with.  The
same argument applies to an MDIO bus, I2C, 1-wire, and more.

And I don't buy it in those cases either.


> I think the question should be flipped around; 
> rather than asking for a compelling reason for them to be merged; I
> want to know the compelling reason to keep them separate.  What is the
> fundamental difference that keeps them apart?

PWM is about periodic signal generation without CPU intervention.

GPIO is about explicit CPU management/interrogation of single
signals.


> What I would like to see is the PWM functions added to the GPIO API.

No.  If you want a pin mux interface, come up with one of them.

It shouldn't be a PWM interface, a GPIO interface, an I2C interface,
a SPI interface, an MDIO interface, a 1-wire interface ... or any of
dozens of other things.  It'd be purely for pinmux.