[PATCH 9/9] net: dsa: mt7530: use external PCS driver

[Andrew Lunn]

> The SerDes PCS units are only available for port 5 and 6. The code
> should make sure that the corresponding interface modes are only used
> on these two ports, so a BUG_ON(!mt753x_is_mac_port(port)) would also
> do the trick, I guess. However, as dsa_port_phylink_mac_select_pcs may
> also return ERR_PTR(-EOPNOTSUPP), returning ERR_PTR(-EINVAL) felt like
> the right thing to do in that case.
> Are you suggesting to use BUG_ON() instead or rather return
> ERR_PTR(-EOPNOTSUPP)?

BUG_ON() is considered to mean something which you cannot recover from
has happened, and going further will only cause more file system
corruption, memory corruption, etc. WARN_ON() is better, since it
gives the user a chance to perform a controlled shutdown, so
potentially not loosing files etc.

But even a WARN_ON() seems a bit extreme. If -EINVAL is sufficient to
cause either the whole device, or the port to fail to probe, that
should be enough to get the DT developers attention. Then either a
dev_err() or a dev_dbg() to help narrow down which check failed.

	  Andrew