Kernel probe order issues

Andriy Gapon avg at icyb.net.ua
Mon Feb 1 09:37:40 UTC 2010


on 01/02/2010 10:51 Peter Jeremy said the following:
> Whilst trying to boot a brand new FreeBSD 8-stable/amd64 kernel,
> I ran into an unfortunate nasty with the kernel probe order.
> 
> This particular box has no PS/2 ports so I have a USB keyboard and
> have removed atkbd et al from my kernel config.  Unfortunately, whilst
> trying to merge changes from 5 different sources, I also accidently
> deleted my HDD controller.  Quite reasonably, the lack of disk
> controller made the kernel spit out an error message and "mountroot>"
> prompt.  Unfortunately, this occurs after the kernel has switched from
> BIOS to its own drivers but _before_ ukbd(4) is probed so I didn't
> have any keyboard.  (Some experimenting with a serial console
> confirmed that ukbd is probed after the root device).
> 
> This strikes me as undesirable.  Is there some way to bump up the
> probe/attach priority of console input devices to ensure that they
> exist before the kernel tries to read input?

It seems to be a problem with either your keyboard or your USB controller.
USB keyboard can be discovered much earlier than mountroot if the hardware is
ready.  No magical software priority bump can help here.


-- 
Andriy Gapon


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