[OLPC-devel] Re: Device tree

[Ronald G Minnich]

Mitch Bradley wrote:
> [Changing name of thread...]
> 
> a) I think we need our own sub-architecture, sooner rather than later.  
> I could give a bunch of reasons, but I suspect that they are obvious to 
> everyone here, considering how little our hardware resembles a legacy PC.
> 
> b) Do we really need PCI autoconfiguration at this point?  The wiki 
> hardware spec doesn't mention the mini-PCI connector.  Can we just 
> pretend that it doesn't exist?  That would remove a lot of variables 
> from the startup and suspend/resume sequence.  Removing unnecessary 
> variables is a Very Good Thing.

I'd say leave it in, as we do wish to let people have at the mini pci 
connector, it is not that expensive to enumerate the PCI (it's a tiny 
tree!), I think the kernel can easily reload all the config info (the 
infrastructure is there and works), and we don't want simple stuff like 
lspci -H1 or -H2 to fail.

I don't think it's really going to kill us.

Also, in an earlier note I outlined an easy way to do the S3 resume from 
the linuxbios side, and one of the smart kernel guys pointed out how 
easy it is to pick that up from the kernel and resume PCI config space. 
I think we're ok.

> 
> c) I will go out on a limb and say that I could add rudimentary OF 
> device tree support to either or both of LinuxBIOS and a custom kernel 
> in a very short time.  Especially if the actual configuration is mostly 
> known.  No methods, just properties.  You may well ask: Why bother with 
> a device tree if the configuration is known?  The answer: Because when 
> we do the 2nd generation hardware and kernel, we will wish that we had.

I could not agree more. I would like to work with you on the linuxbios 
side, so we can add it in as a linuxbios device, and make sure it gets 
done in conformance with how linuxbios works -- stefan and richard are 
also able to help here.

And, if this could grow to real OF properties support in linux for the 
long term, it's a good thing. The alternatives (ACPI and EFI) are just 
disgusting.

thanks

ron