Re: [PATCH] parport_pc.c PnP BIOS sanity check

Eric W. Biederman
2001-08-10T09:25:18Z

"H. Peter Anvin" <hpa@zytor.com> writes:

> Followup to: <E15UV8M-0005SE-00@the-village.bc.nu>
> By author: Alan Cox <alan@lxorguk.ukuu.org.uk>
> In newsgroup: linux.dev.kernel
> >
> > > The following would seem to be required to protect against
> > > the case in which PnP BIOS reports an IRQ of 0 for a
> > > parport with disabled IRQ. // Thomas jdthood_AT_yahoo.co.uk
> >
> > IRQ 0 is a legal valid IRQ. I suspect the problem is that pnpbios shouldnt
> > be reporting an IRQ or we should be using some kind of NO_IRQ cookie
> >
>
> IRQ 0 is hardwired to the system timer in PC systems, though, so it
> could simply be assumed that IRQ 0 will never be used for any other
> purposes.
>
> Reminds me back in the days when you had to worry about DRQs as well;
> DRQ 0 was hardwired in the original PC but then became available in
> the AT; there was a whole bunch of things that assumed DRQ 0 wasn't
> usable, even though it was perfectly fine. Not to mention the
> motherboard I had which would lock up solid if anything ever used
> DRQ 5.
>
> Good riddance, all this crap...

If we are going to list all of the silly assumptions, we still have
the assumption that 640KB-1MB on x86 cannot be used as ram. It is
less painful but still annoying when you put perfectly valid ram
there. :)

Eric