[Power.org:parch] devicetree: Musings on reserved regions

[Jimi Xenidis]

On Feb 8, 2011, at 12:45 AM, Benjamin Herrenschmidt wrote:
> 
> On Mon, 2011-02-07 at 22:05 -0700, Grant Likely wrote:
>> 
>> Hmmm, of all the ideas, I think I like this one the best.  It is a
>> little more verbose than I was thinking, but making each reserved
>> region (or set of reserved regions) have separate node has some very
>> real advantages.  For one, the address decoding *just works* with our
>> existing helpers.  Also it means that device nodes can directly
>> indicate the reserved regions associated with it by way of a phandle.
> 
> But that means that anything that needs to setup a simple memory
> allocator (and thus needs to know what to avoid) will need to walk the
> entire tree for nodes with a "reserved" property, be able to parse
> addresses down to that node (not always obvious accross some bus types),
> etc...
> 
> Or do we propose to keep a "consolidated" reserve map in addition to
> having nodes self-describe which part of this reserve map they are
> responsible for, which thus gives the OS the option to:
> 
> - Reserve it all
> - Then, based on specific knowledge of some nodes, maybe release
> or juts "tag" (for diag purposes) portions of reserved memory

Excellent point.
I always thought we were keeping the reservation list and it starts "anonymous".
Only later to we want to "name" it.
We could define a standard property (for any node) called "reserved" that is the range within the list.
I suppose if it is empty, then it is all of "reg"
-JX


> 
> Ben.