Re: RFC: gpio attachment for ppbus

[der Mouse <mouse%Rodents.Montreal.QC.CA@localhost>]

> Second, ppbus is extended to attach a gpiobus which supports 17 pins
> of the parallel port (the remaining pins are hardwired to GND).
> There are 12 output pins and 5 input pins, and it is not possible to
> change their direction or set any other characteristics.  A few pins
> are inverted by the hardware, the driver knows about them and adjusts
> the values read or written accordingly.  The ppbus(4) and gpio(4)
> manpages are updated, too.

> Please comment.  If possible, I would like to see this in 5.0 :)

I like it.  I've recently been doing a lot of parallel-port-driven
electronics, and I have hacks in the lpt driver for the purpose.  It'd
be good to have a non-hacky way to do that.

One thing I would suggest is that you document which order the data
pins and the control pins are written in, when changing both.  (Or does
the scaffolding allow userland to control that order?  I don't know
gpiobus.)

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