Hi Grant,

On Mon, Jun 13, 2011 at 07:32:15AM -0600, Grant Likely wrote:
[...]

+Linux board support code calls of_platform_populate(NULL, NULL, NULL)
+to kick of discovery of devices at the root of the tree.  The
+parameters are all NULL because when starting from the root of the
+tree, there is no need to provide a starting node (the first NULL), a
+parent struct device (the last NULL), and we're not using a match
+table (yet).  For a board that only needs to register devices,
+.init_machine() can be completely empty except for the
+of_platform_populate() call.
+
+In the Tegra example, this accounts for the /soc and /sound nodes, but
+what about the children of the soc node?  Shouldn't they be registered
+as platform devices too?  For Linux DT support, the generic behaviour
+is for child devices to be registered by the parent's device driver at
+driver .probe() time.  So, an i2c bus device driver will register a
+i2c_client for each child node, an spi bus driver will register
+it's spi_device children, and similarly for other bus_types.
+According to that model, a driver could be written that binds to the
+soc node and simply registers platform_devices for each of it's
+children.  The board support code would allocate and register an soc
+device, an soc device driver would bind to the soc device, and
+register platform_devices for /soc/interrupt-controller, /soc/serial,
+/soc/i2s, and /soc/i2c in it's .probe() hook.  Easy, right?  Although

I do not quite understand what the "soc device driver" is here.
Looking at the devicetree/test code, I do not find this driver and
its .probe() hook.  Instead, of_platform_bus_create will create
platform_device for the provided device_node, and also recursively
create devices for all the child nodes, no?

+it is a lot of mucking about for just registering platform devices.
+

-- 
Regards,
Shawn