On Tue, Jun 14, 2011 at 8:05 AM, Far McKon far.mckon@buglabs.net wrote:

Grant, I don't see any system for indicating an expandable bus or a pulg in module so far? Am I missing something, or does this protocol/layout not allow for plug in or expansion modules?

The DT as we're using it now primarily captures the static structure of the system. Typically this means anything directly on-board, or unlikely to ever be hot-plugged (like a CPU module on a carrier board). The DT is expressive enough to capture the details of plugged in modules, but in general if the device can be detected and identified reliably by the hardware (like USB and PCI devices), then there is no real need to describe it in the DT.

With 'real' OpenFirmware, the firmware did indeed enumerate hot plugged devices in the DT, but we don't do that at all for the firmware using the flattened tree.

That said, you may have a need to describe the internal details of a plug in module, and you could do that with DT. XIlinx has done some work that allows a partial DT to be passed in at runtime to describe the behaviour of an FPGA module after it has been programmed with a bitstream.

g.