Autoconfig

[Chris Torek]

In article <9600 at eddie.MIT.EDU> nessus at athena.mit.edu (Doug Alan) writes:
>I'm led to believe from reading "Building Berkeley UNIX* Kernels with
>Config", that if your system works, you should be able to power down
>your system, pull out a controller from the bus (replacing it with a
>grant card), and reboot the system, and your system will still boot,
>as long as the controller that you removed wasn't critical for booting.

More or less.

>... For some boards it works. ... For some controllers, the system hangs
>when it gets to the point in the autoconfig sequence where the missing
>controller would normally be found.

This is probably a driver bug: one that does something like

	((struct foodevice *)reg)->csr = FOO_INIT;
	while ((((struct foodevice *)reg)->csr & FOO_DONE) == 0)
		/* spin */;

or something equally wrong.

>A more peculiar mode of failure happens when I remove a second dis
>controller.  The autoconfig sequence finds the first controller twice!
>And both times it finds it at the same CSR address.

A small bug, fixed in 4.3BSD-tahoe.  (The test for ualloc[addr] is missing.)

>... We [also] have a uVax-II with two [Sigma] controllers and the
>aforementioned kernal.  It also has a Wespecorp tape controller.
>I want to put in a DHV11, but whenever I do, it doesn't work right.
>With the DHV11 in, autoconfig seems to find it fine, but if I try
>to [use it] it hangs. ... Another problem that seems to occur with
>the DHV11 in, is that some C programs, occasionally, when trying to
>dump core, cause the whole system to become wedged.

Sounds like either a hardware problem or a bug in one of the drivers
that hogs Unibus (Qbus) map resources.
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7163)
Domain:	chris at mimsy.umd.edu	Path:	uunet!mimsy!chris