Re: FT u-boot shim

[Tom Rini <trini@kernel.crashing.org>]

On Fri, Apr 28, 2006 at 11:01:20AM -0500, Kumar Gala wrote:

> However, I really hate introducing some third project that is  
> required.  If we decide to pull ALL of boot wrappers out of the  
> kernel tree than I'd be ok with it.  But until that time I think this  
> lives under arch/powerpc/boot/...

The more I think about this, and hear about what some vendors do,
pulling arch/p*pc/boot/ out of the kernel is making more and more sense.
Especially with the serial headache, a depends-on-nothing,
can-translate-$(firmware information) tool might be best.

> What I envision as the way one boots for something like u-boot is one  
> of three options:
> 1. using an old u-boot + boot wrapper (bd_t -> wrapper -> kernel)
> 2. using a u-boot that is ft aware + dtb (boot command in u-boot  
> takes kernel & dtb images, updates blob and passes to kernel)
> 3. using a u-boot that is ft aware + built in dtb.

And more generally:
1. using an old firmware + kernel boot wrapper (firmware->dtb converter)
boots kernel.
2. using a dtb-aware firmware boots kernel (compressed or not) and
passes dtb in.

> The issue is that for a given system/board you may need to support  
> multiple or all three.  This raises the question where does the .dts  
> live.  For the time being I say it lives in the boot wrapper part of  
> the kernel tree.  Thus we handle the three cases as follows:

We could stick it in the seprate kernel boot wrapper project.  But I
really think this really has to live in two places.  The kernel should
be The Owner, as until *BSD or something adopts this, it's a
Linux-specific thing.  But any firmware that wishes to skip the kernel
boot wrapper and be a direct kernel booter, will need to own a copy.

-- 
Tom Rini
http://gate.crashing.org/~trini/