building RaspPi Images

[Tim Kientzle]

On Feb 12, 2013, at 8:40 AM, Warner Losh wrote:

> The typical approach taken over in linux-land is to have a base config, then have customizations done with a file that just includes the base, and enables some of the disabled devices. You don't need several versions of the DTS at all, just one base one and several smallish files that describe different board configs.  Think of this as:
> 
> include "GENERIC"
> nodevice foo
> device bar
> option FRED
> nooption WILMA
> 
> FDT is powerful enough to cope with those things today, with the version we have in the tree.

Warner,

Could you point me to a good example of this?

I've dug around a little bit in the Linux DTS files
but I'm not sure I yet understand what I'm looking
at well enough to tell which ones are good examples
of this technique in action.

I also have a question about FDT device probe
ordering:  I found in tinkering with BeagleBone that
our current FDT implementation probes each
device in the order it appears in the FDT.
This caused me some confusion when I accidentally
had some device (I don't remember which one; call
it FOO) before the SCM controller (which handles pinmux).
The FOO attach blew up because it couldn't
get access to the SCM controller.  (Yes, the FOO
driver did explicitly list SCM as a requirement.)

I wonder if simple bus shouldn't somehow
accommodate this; otherwise, it seems like
it could be a problem for doing DTS inclusion
correctly.

Tim