On Sat, Feb 11, 2023 at 04:50:39PM +0100, Andrew Lunn wrote: > I'm not sure that is true. The switches probe method should register > with the driver core any resources a switch provides. So switch #1 > MDIO bus driver is registered during its probe, allowing the probe of > switch #2 to happen. When switch #2 probes, it should register its > clock with the common clock framework, etc. > > However, the linking of resources together, the PTP clock in your > example, should happen in the switches setup() call, which only > happens once all the switches in the cluster have probed, so all the > needed resources should be available. > > Because we have these two phases, i think the above setup would work. I was thinking it wouldn't work because the PTP timer sub-driver would first have to request the clock input from the CCF, before registering its own clock output with the CCF. So the driver writer would be forced to request a clock from the CCF in the probe() phase, if it wanted to also register as a clock provider in the probe() phase. I.o.w., switch #1 would get an -EPROBE_DEFER waiting for the clock from switch #2, before it would get to call dsa_register_switch(). TLDR: the rule "provide all you have in stage 1, request all you need in stage 2" would only work if you don't need anything to register your providers.
