Subject: Re: [PATCH] powerpc: make the padding for the device tree a configurable option

From: Benjamin Herrenschmidt <[email-masked]>
Date: Thu, 20 May 2010 08:44:10 +1000

On Wed, 2010-05-19 at 16:33 -0500, Timur Tabi wrote:
> Benjamin Herrenschmidt wrote:
> 
> >> So to accommodate future boards where more padding is needed, we make the
> >> option for the -p parameter configurable.
> > 
> > Can't u-boot just allocate more space ?
> 
> Yes and no.  U-Boot has functions to increase the size of an fdt, but these
> functions can't be sure that the fdt will grow beyond its allocated space.
> So if U-Boot calls fdt_setprop() or fdt_add_subnode(), and there isn't
> enough space in the fdt, those functions will return with an error.

 .../...

It's still not kernel business to have to deal with u-boot memory
allocation constraints. The padding in the kernel built is intended to
make space for DT changes done by the zImage wrapper.

Maybe we could add to libfdt a way to provide a realloc() callback to it
when it hits the max size, and uboot can then move things around (or
fail).

Ben.