Re: [PATCH] x86: provide a DMI based port 0x80 I/O delay override.

[Christer Weinigel <christer@weinigel.se>]

On Tue, 1 Jan 2008 17:43:38 +0100
Ingo Molnar <mingo@elte.hu> wrote:

> if someone runs a fresh new kernel on an ancient device then timings 
> _will_ change a bit, no matter what we do. Alignments change, the 
> compiler output will change (old compilers get deprecated so a new 
> compiler might have to be picked), cache effects change - and this is 
> inevitable. The important thing is to not eliminate the delays - but
> we sure dont have to keep them cycle accurate (we couldnt even if we
> wanted to). The only way to get the _exact same_ behavior is to not
> change the kernel at all.

What I'm afraid is that udelay will be significantly slower, which
might hit anything that does a lot of gettimeofday calls (poking at the
PIT timer)  on embedded 386/486 systems.  On the other hand, those
systems might not want to upgrade to 2.6 anyway.  

And why do people keep buying HP hardware?  HP seem to be quite
Linux-unfriendly on the desktop [1] and on their laptops.  Apparently
HP doesn't even bother to try Linux on any of their non-server systems.

[1] Try running Linux on a HP DC7700 machine, there seems to be a lot
of magic stuff in those machines that doesn't work well with Linux.
They had some ACPI crap that stopped FC7 from booting without a lot of
magic PCI access options and audio still does not work.  

/Christer