Since kernel 4.12, the function bond_miimon_commit in the bond interface refuses to setup a slave interface which does not report speed / duplex information. In my particular use case I bond ethernet and wifi (iwlfifi) interfaces in active-backup mode. The update to 4.12 broke my network, since the wifi interface does not seem to report speed / duplex information.

I guess it can be argued that some bonding modes require that information to make decisions, but not all modes do, for example round-robin or active-backup. I see no rationale for failing to setup the slave, at least, in those modes.