Appended devicetree with Torvalds' HEAD

[Nicolas Pitre]

On Thu, 8 Sep 2011, Linus Walleij wrote:

> On Tue, Sep 6, 2011 at 9:24 PM, Linus Walleij <linus.walleij at linaro.org> wrote:
> > On Tue, Sep 6, 2011 at 7:52 PM, Nicolas Pitre <nicolas.pitre at linaro.org> wrote:
> >
> >> They sure do, (or so I hope).
> >> My latest patchset is here:
> >
> > OK I have cloned your git and already made some minor adjustments,
> > will return with more details when/if I get this going.
> 
> Hm it doesn't boot, if I configure out the DT support it
> works fine. (On v3.1-rc4 and ux500) How typical :-/
> 
> I tried to regression-test it on a legacy system but then
> I ran into a problem that may be serious: that platform does
> not use a compressed zImage, it users the plain vmlinux
> converted to binary with objcopy.
> 
> Is there a particular reason why we want to append the
> device tree to the zImage rather than to vmlinux?

Absolutely.

The ultimate goal of DT is to separate the board configuration data from 
the kernel image.  This is why we expect all bootloaders to provide this 
DTB eventually, so that the kernel could be upgraded at will, and even 
booted on future boards unchanged.

So this ability to simply append the DTB to a zImage is just a 
convenience to accommodate legacy bootloaders.  It should _not_ become 
the primary way of providing a DTB to the kernel.  At least by appending 
it to zImage it can be done independently from the kernel build process 
and performed right before the kernel is stored on the boot media.


Nicolas