[U-Boot-Users] Can U-boot Autodetect arch/ppc versus arch/powerpc from info in the uImage?

Wolfgang Denk wd at denx.de
Mon Dec 3 22:36:14 CET 2007

In message <D61182AC8012EA4EBC531B3AF23BE109480232 at tranzeo-mail2.12stewart.tranzeo.com> you wrote:
> I have looked at some of the u-boot code for booting up a linux kernel.
> It appears that the determination of whether or not to make use of
> flattened device tree (fdt) in the boot is a compile time selection.

No, this is not the case. You can use a FDT-enabled U-Boot to boot
kernel images which use a FDT, and of course such that don't, too.

> Can we determine during runtime from info in the uImage whether the
> linux kernel was built as arch/ppc or as arch/powerpc and then select
> the fdt support accordingly?

No. There is no such information available in the current image

> It will soon be possible to build a U-Boot for one or the other (for
> ppc4xx family).  I think I will need to implement a U-Boot that will

This is not correct. You can build U-Boot  without  FDT-support,  and
this will only work with old (arch/ppc) kernels, or with arch/powerpc
kernels  using  the  bootwrapper  (cuImage).  Or you can build U-Boot
*with* FDT-support, which can do exactly the  same,  *plus*  directly
boot FDT enabled Linux kernels.

> I think we need the U-Boot to be able to support both but detect which
> one the uImage was built under.

The first part of the sentence is true, and describes the current
state of things, and the second part is IMO not needed.

> In the image.h file, there appears to only be one selection for powerpc
> so there will likely be need for some other "magic" to make this work.
> Has anyone checked into this before, or come up with a workable
> solution?

I see no need for any such changes.

Best regards,

Wolfgang Denk

DENX Software Engineering GmbH,     MD: Wolfgang Denk & Detlev Zundel
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
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