On Fri, Dec 23, 2022 at 09:44:14AM +0100, Krzysztof Kozlowski wrote:
just trim the code... we do not need to scroll over unrelated pieces.
ok
quoted
However, the irq_domain/irqchip handling code in this case will go to
drivers/net/dsa/, and it won't really be a "driver" (there is no struct
Why? Devicetree hierarchy has nothing to do with Linux driver hierarchy
and nothing stops you from putting irqchip code in respective directory
for such DT. Your parent device can be MFD, can be same old DSA switch
driver etc. Several options.
True, in fact I've already migrated in my tree the drivers for
nxp,sja1110-base-tx-mdio and nxp,sja1110-base-t1-mdio (which in the
current bindings, are under ethernet-switch/mdios/mdio@N) to dedicated
platform drivers under drivers/net/mdio/. The sja1105 driver will have
to support old bindings as well, so code in sja1105_mdio.c which
registers platform devices for MDIO nodes for compatibility will have to
stay.
But I don't want to keep doing that for other peripherals. The irqchip
is not a child of the ethernet-switch, not in any sense at all. The
ethernet-switch even has 2 IRQ lines which need to be provided by the
irqchip, so there would be a circular dependency in the device tree
description if the ethernet-switch was the parent.
fw_devlink doesn't really like that, and has been causing problems for
similar topologies with other DSA switches. There have been discussions
with Saravana Kannan, and he proposed introducing a FWNODE_FLAG_BROKEN_PARENT
flag, that says "don't create device links between a consumer and a
supplier, if the consumer needs a resource from the supplier to probe,
and the supplier needs to manually probe the consumer to finish its own
probing".
https://patchwork.kernel.org/project/netdevbpf/cover/20210826074526.825517-1-saravanak@google.com/
That patch didn't really go anywhere to my knowledge, but I'd prefer to
sidestep all that discussion about what constitutes a broken parent and
what doesn't, and here, introducing an irqchip driver which is a fwnode
child of the ethernet-switch driver seems like a big mistake, given past
experience.
I omitted this because I wanted to give you a bit of context, but I felt
like some of it was outside the scope of my real question, which is
mostly about how to deal with IORESOURCE_REG resources through generic
OF address code.