Re: fwnode_for_each_child_node() and OF backend discrepancy

[Michael Walle]

> > I was trying to fix the lan966x driver [1] which doesn't work if there
> > are disabled nodes in between.
>
> Can you elaborate what's wrong now in the behaviour of the driver? In
> the code it uses twice the _available variant.

Imagine the following device tree snippet:
 port0 {
   reg = <0>;
   status = "okay";
 }
 port1 {
   reg = <1>;
   status = "disabled";
 }
 port@2 {
   reg = <2>;
   status = "okay";
 }

The driver will set num_phys_ports to 2. When port@2 is probed, it
will have the (correct!) physical port number 2. That will then
trigger various EINVAL checks with "port_num >= num_phys_ports" or
WARN()s.

So the easiest fix would be to actual count all the child nodes
(regardless if they are available or not), assuming there are as
many nodes as physical ports.

But num_phys_ports being a property of the hardware I don't
think it's good to deduce it by counting the child nodes anyway,
but it should rather be a (hardcoded) property of the driver.

-michael

[1] 
https://elixir.bootlin.com/linux/v5.19-rc4/source/drivers/net/ethernet/microchip/lan966x/lan966x_main.c