Hi All,
I have few queries on of_platform_populate and of_platform_bus_probe functions.
Use-case is, I want to explicitly register platform devices from some nodes at
post-core or late-init level(like child@1).
And I don't want of_platform_populate to register platform devices for that
node again, so I pass "simple-bus" in match-table.
Problem is that exiting code for of_platform_populate probes it.
Looking at the function documentation, which states
of_platform_bus_probe will only create children of the root which are
selected by the @matches argument.
of_platform_populate walks the device tree and creates devices from
nodes. It differs in that it follows the modern convention of requiring
all device nodes to have a 'compatible' property, and it is suitable for
creating devices which are children of the root node.
Lets say If we call of_platform_populate(NULL, match_table, NULL, NULL)
on a device trees like the below with
struct of_device_id match_table[] = {
{ .compatible = "simple-bus", }
{}
};
parent@0{
compatible = "xxx,parent1", "simple-bus";
...
child@0 {
compatible = "xxx,child0", "simple-bus";
...
};
child@1 {
compatible = "xxx,child1";
...
};
child@2 {
compatible = "xxx,child2", "simple-bus";
...
};
};
of_platform_bus_probe would create platform-devices for parent@0,
child@0 and child@2
where as
of_platform_populate would create platform-devices for parent@0,
child@0, child@1 and child@2 nodes.
So the question is
why do we need to have @matches argument to of_platform_populate in the
first place, if it creates all the devices by walking the dt nodes?
It is bit confusing, As some platforms use of_platform_populate(NULL,
of_default_bus_match_table, NULL, NULL) assuming that only matching
nodes will end up having platform device.
Also
some platforms use of_platform_bus_probe(NULL, match_table, NULL),
where match table is of_default_bus_match_table.
Am not 100% sure what is the right solution, but I think lot of platforms would
want behavior like of_platform_bus_probe which takes lookups aswell.
If the suggestion is to use of_platform_bus_probe, Which I can't use as It does
not take Auxdata(lookups).
Thanks,
srini
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