Device tree with early buffer allocations and aliased memory

[David VomLehn]

On Tue, Nov 09, 2010 at 10:25:37PM -0600, Grant Likely wrote:
> On Wed, Nov 03, 2010 at 01:50:37PM -0700, David VomLehn wrote:
> > This got eaten as junk mail, so pardon the slow response. Also, Stuart
...
> > On Sat, Oct 30, 2010 at 10:57:34PM -0500, Grant Likely wrote:
> > > On Wed, Oct 27, 2010 at 2:49 PM, David VomLehn <dvomlehn at cisco.com> wrote:
...
> > This still leaves the question of buffers. Buffers with statically and
> > dynamically assigned addresses need some sort of identifier so that
> > they can be referenced by device drivers. There may be more than one
> > buffer per device and a single device may use buffers with statically
> > assigned addresses and buffers with dynamically assigned addresses.
> > Buffers with statically assigned buffers addresses could be handled
> > with something like:
> > 
> > 	device-s {
> > 		compatible = "cisco,device-s";
> > 		cisco,static-buffers = 
> > 			"device-s-b1",<0x24000000 0x00100000>,
> > 			"device-s-b2",<0x60000000 0x00200000>;
> 
> Or, simply:
> 	cisco,static-buffer-b1 = <0x24000000 0x00100000>;
> 	cisco,static-buffer-b2 = <0x60000000 0x00200000>;
> 
> Try to avoid mixing string and cell values in the same property where
> appropriate.  Sometimes doing so is the best binding, but those cases
> are rare.

I started implementing the 'cisco,static-buffer-b1' solution and it feels pretty awkward.
When I want to get the property value, I have to know not only the constant property
name but also a buffer name. The buffer name is really one of the pieces of data I
want to get. I can, of course, write code to scan the node and do a partial match on
the property name, but that doesn't feel like the rest of the DT API.

Not only does this have me doing odd things to property names, but I have a number of
devices. If I should want another buffer, I must create another property name.
This solution has me creating a bunch of property names, which all I really
want is two: "cisco,static-buffers" and "cisco,dynamic-buffers".

I think this is an occasion where it makes sense to mix string and cell values in the
same property.

> g.

-- 
David VL