[RFC] consolidated libdt proposal

[Mark A. Greer]

Hi Hollis,

On Mon, Aug 07, 2006 at 04:58:41PM -0500, Hollis Blanchard wrote:
> On Sun, 2006-08-06 at 19:38 -0500, Hollis Blanchard wrote:
> > 
> > Hmm, so we'll have at least three copies of this code: uboot, kernel,
> > and Xen. Would it make sense to put this stuff into a libdt.a?
> > Technically, dtc has a "libdt" already, but it's absurdly incomplete
> > (I don't even know why it's there), so we could just replace it. 
> 
> Mark, I had a look at the code Pantelis wrote for u-boot, and it was
> pretty easy to adapt to meet Xen's (userspace-based) needs. I've
> attached my version below (and see ft_setup() at the bottom of the
> file). Does it meet your requirements for the kernel bootwrapper?

[Disclaimer: I did a fairly quick scan of your patch so I may have
misread or missed something.]

Except for not being able to extend a property (see below),
I think it does meet my needs (at least as I know them today).

However, I was hoping to keep the interfaces in the bootwrapper
similar to the ones used in the kernel.  To that end, I had a
routine to find a device node and other routines to find and modify
a property within that node.  I didn't notice a "finddevice" type of
function to find a device node.  Would you have a problem adding one?

> One limitation of the attached code is that it doesn't support changing
> the *size* of properties, though I don't think that would be too
> difficult to add if needed.

If we're going to allow cmdline editing in the bootwrapper, we would
need to extend the size of a property.  We've never really talked about
cmdline editing in the powerpc branch but I assume that its a good
thing(tm).  I know I would like to have it so, IMHO, I think we should
add it (and therefore require extending a property).

Mark