Grant Likely wrote:
On Tue, Jul 08, 2008 at 02:26:32PM +1000, David Gibson wrote:
Does anyone on this list have contacts with the makers of this board?
Its firmware apparently provides a flattened device tree to the OS.
And while this step towards world domination is flattering, it's an
example of what I feared when people first got enthusiastic about the
idea of including flattened device trees in firmwares. The tree has
not, AFAIK, been past this list, and has apparently not been reviewed
by someone knowledgeable about device trees. In short, it's crap, and
now that it's embedded in the firware we can't really fix it.
So, to any embedded hardware/firmware vendors doing Linux ports out
there. I certainly encourage you to use flattened device trees, but
can I please suggest you put the blob into your kernel image (in the
bootwrapper strictly speaking), rather than into the flashed firmware.
It's a lot easier to fix mistakes that way.
There are situations where it's nice to have the device tree in
firmware, but there are many others where it buys little to nothing.
People seem to be a bit overenthusaistic on the concept at the moment.
Total Ack! Allow me second that opinion.
g.
I'm a half-ack. ;-) I'm partial to u-boot's implementation rather than
using a bootwrapper for obvious reasons. The u-boot implementation
takes the blob as a boot parameter and passes it along to the kernel
after doing appropriate (optional) fixups. The usual implementation is
to burn it into a block of flash separate from u-boot itself or use tftp
to load it from the server.
Other than that quibble, I agree that burning the blob into the firmware
so that the firmware must be recompiled and reburned to change the blob
is very undesirable.
Best regards,
gvb
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