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Since 2014, the DSA OF bindings support the > > +``phy-handle`` property, which is a universal mechanism to reference a PHY, > > +be it internal or external. > > + > > +New switch drivers are encouraged to require the more universal ``phy-handle`` > > +property even for user ports with internal PHYs. This allows device trees to > > +interoperate with simpler variants of the drivers such as those from U-Boot, > > +which do not have the (redundant) fallback logic for ``ds->user_mii_bus``. > > Considering this policy, should we not emphasize that ds->user_mii_bus > and ds->ops->phy_{read,write}() ought to be left unpopulated by new > drivers, with the remark that if a driver wants to set up an MDIO bus, > it should store the corresponding struct mii_bus pointer in its own > driver private data? Just to make things crystal clear. > > Regardless I think this is good! > > Reviewed-by: Alvin Šipraga I think something that makes a limited amount of sense is for DSA to probe on OF, but not describe the MDIO controller in OF. Then, you'd need ds->user_mii_bus. But new drivers should probably not do that either; they should look into the MFD model and make the MDIO controller be separate from (not a child of) the DSA switch. Then use a phy-handle to it. So for new drivers, even this doesn't make too much sense, and neither is it best to allocate the mii_bus from driver private code. What makes no sense whatsoever is commit fe7324b93222 ("net: dsa: OF-ware slave_mii_bus"). Because DSA provides ds->user_mii_bus to do something reasonable when the MDIO controller isn't described in OF, but this change assumes that it _is_ described in OF! I'm not sure how and where to best put in words "let's not make DSA a library for everything, just keep it for the switch". I'll think about it some more.