Russell King - ARM Linux Admin wrote:
>
> Philip Blundell writes:
> > as the console could. On platforms where the interrupt lines are fixed
> > (NetWinder and CATS for example, but not EBSA-285) it can do everything.
>
> Indeed - totally embedded machines like the NetWinder it is a good idea
> since you know 100% what you're dealing with. However, when talking about
> a plug in card, I'd rather not have 50 different initialisation themes in
> the kernel.
>
> > Also, experience shows that we tend to end up having code in the kernel to go
> > through and fix up things that the console didn't do the way we wanted them in
> > any case. We might as well not bother and just let the kernel do the whole
> > lot in the first place.
>
> I have two points here:
>
> 1. the kernel cannot possibly know the way the bus needs to be set up
> in every case.
>
Well, err, yes it can. The Alpha/MIPs cases work on a huge variety of
systems. The kernel can know as well as a BIOS how to set up a PCI subsystem.
> 2. a freebios could set up the PCI bus how we wanted it in the first place,
> while releaving the kernel of the task of knowing system X, Y and Z's
> peculiarities.
In this case, so long as you implement the PCI BIOS bits - these include
query callbacks to discover the PCI topology - then this is a perfectly
valid approach. Its advantage would be that the kernels could remain
(or become) generic. Of course, you'd still have to port the BIOS but that
couldn't be harder than porting a kernel.
I'm not saying that this is the right approach, but for MILO I embedded real
Linux device drivers into an environment that was a cut-down Linux kernel.
The advantage was the enormous set of device drivers, the disadvantage was
the need to have the code in the kernel in the first place. If your BIOS
can be simpler then all to the good. Have you seen uHAL?
Dave
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