GPIO revisited

[Marc Balmer <marc%msys.ch@localhost>]

NetBSD has had support for General Purpose Input/Output devices since  
the 4.0 release, when the GPIO framework from OpenBSD 3.6 was  
imported. Since the import of the GPIO framework into NetBSD, I have  
reworked larger parts of that subsystem in OpenBSD to address some  
problems and drawbacks (see http://www.vnode.ch/reworking_gpio for  
motivation and details).

I have now prepared these changes and more for NetBSD and continued to  
improve on them. The new GPIO framework retains backwards  
compatibility while adding new features: it integrates with the  
kauth(9) security framework, has it's own config file format  
gpio.conf(5), and integrates with the system startup scripts in /etc/ 
rc.d.

As the old API has been kept for backwards compatibility, a new API  
has been introduced, which means that we will loose compatibility with  
OpenBSD on the API level, the command line interface, however, is the  
same (for now).

Over the last weeks I have discussed my work with tron, tonnerre,  
dyoung, wiz, and jmcneill (thanks, guys!).  The diff has gone through  
several iterations already and is commit-ready, imo.  Nevertheless I  
want to give you an opportunity to look at it and comment on it before  
I finally commit it.

The most preeminent changes from a user perspective are...
	... a much more natural command line syntaxt, e.g. "# gpioctl gpio0  
error_led on" and a configuration file /etc/gpio.conf

The most preeminent change from a technical level is...
	... that drivers using gpio pins can be attached (and detached) at  
runtime, no longer a custom kernel configuration is needed. e.g "#  
gpioctl gpio0 attach gpioow 6 1"

The most preeminent change from a security point of view is...
	... that the gpio layout can be locked by integration with the  
kauth(9) framework, preventing layout changes at securelevel > 0  
(securlevel being handled through the securelevel kauth module)

The diff itself can be found online at http://www.netbsd.org/~mbalmer/diffs/gpio_13.diff 
.  I have left older versions of the diff there as well for your  
amusement.  Apply it against NetBSD -current.

Please make sure that you also check for higher numbered gpio diffs,  
as I might put a new diff online if I have to change sth.  Stay tuned  
to http://www.netbsd.org/~mbalmer/diffs/ ;)

- Marc Balmer