Re: Representing Embedded Architectures at the Kernel Summit

[Geert Uytterhoeven <geert.uytterhoeven@gmail.com>]

On Tue, Jun 2, 2009 at 23:10, Russell King <rmk@arm.linux.org.uk> wrote:
> On Tue, Jun 02, 2009 at 11:29:46AM -0600, Grant Likely wrote:
>> Embedded PowerPC and Microblaze has tackled this problem with the
>> "Flattened Device Tree" data format which is derived from the
>> OpenFirmware specifications, and there is some interest and debate (as
>> discussed recently on the ARM mailing list) about making flattened
>> device tree usable by ARM also (which I'm currently
>> proof-of-concepting).
>
> Note that I have to point out that ARM will probably never be in a
> situation where you can have a one kernel image boots on everything.
> That _is_ practical today (and does happen with all PXA now) with what
> we have within a very big restriction - which is that the kernel must
> be built to support PXA and not Atmel SoCs.
>
> I really don't think combining SoC support is going to be realistic,
> device tree or not.  When we had just four machine types (RiscPC,
> EBSA110, EBSA285, Netwinder) I did look into this and came to the
> conclusion that it would be far too inefficient for there to be any
> win.
>
> The big problem we have is that the only commonality between different
> SoCs is that the CPU executes ARM instructions.  Everything else is
> entirely up to the SoC designer - eg location of memory, spacing of
> memory banks, type of interrupt controller, etc is all highly SoC
> specific.  Nothing outside of the ARM CPU itself is standardized.

That sounds very similar to m68k, which does support generic kernels
(except for Sun-3, which uses a completely different MMU)?

Gr{oetje,eeting}s,

						Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
							    -- Linus Torvalds