On Mon, 4 Apr 2011, Eric Miao wrote:
> >> * And very hardware specific code moved out to a controllable place,
> >> i.e. something like BIOS
> >
> > Sorry, but I must vehemently disagree here. BIOSes are a problem for
> > Open Source, not a solution. On X86 they use BIOS services only when
> > there is simply no other choice, because the BIOS is too often buggy and
> > it is more difficult and risky to update than the kernel.
> >
> > If you rely on the BIOS to do X, it will work when the BIOS gets it
> > right. If you do X yourself, it will work whether or not the BIOS gets
> > it right. This means that if there's even one BIOS version you have to
> > deal with out there that gets X wrong, you have to do it yourself and
> > then there is no incentive to rely on the BIOS even in the cases where
> > it does get it right so to maintain only one code path.
> >
> > And relying on a BIOS could make many kernel improvements impossible to
> > implement as the execution context assumed by the BIOS may not be
> > guaranteed anymore (think about UP vs SMP, different preemption modes,
> > different realtime kernel modes, etc.) And of course it is impossible
> > to anticipate what execution context and requirements the kernel might
> > need in the future, hence this can't be provisioned for (and much less
> > validated) into the BIOS design in advance.
>
> Not BIOS exactly, since we don't have BIOS for ARM. The problem with
> BIOS is that we don't have control, and when it's wrong we have nowhere
> to fix it.
>
> There are some ways out - e.g. if u-boot is standardized, we can
> definitely move part of the non-generic code there. Or I'm actually
> still thinking about using kernel as a bootloader, though not very clear
> on how, and we may still end up placing crap there... :-)
BIOS/firmware/bootloader. It's all the same thing when it comes to
updating them in deployed hardware: it is harder and much risquier than
updating the kernel or some DT data in the bootloader's environment.
And there is real danger of version skews that were never tested and
planned.
Standardizing on U-Boot is not a given. Many real devices out there are
not using it.
I still like the idea of using the kernel as a bootloader. But once
you've put the crap in there, some people will be tempted to simply use
the same working crap in the real kernel. Hence better make that crap
into something palatable from the start.
Nicolas
_______________________________________________
linaro-dev mailing list
linaro-dev@lists.linaro.org
http://lists.linaro.org/mailman/listinfo/linaro-dev
