net: dsa: felix: reimplement tagging protocol change with function pointers

The error handling for the current tagging protocol change procedure is
a bit brittle (we dismantle the previous tagging protocol entirely
before setting up the new one). By identifying which parts of a tagging
protocol are unique to itself and which parts are shared with the other,
we can implement a protocol change procedure where error handling is a
bit more robust, because we start setting up the new protocol first, and
tear down the old one only after the setup of the specific and shared
parts succeeded.

The protocol change is a bit too open-coded too, in the area of
migrating host flood settings and MDBs. By identifying what differs
between tagging protocols (the forwarding masks for host flooding) we
can implement a more straightforward migration procedure which is
handled in the shared portion of the protocol change, rather than
individually by each protocol.

Therefore, a more structured approach calls for the introduction of a
structure of function pointers per tagging protocol. This covers setup,
teardown and the host forwarding mask. In the future it will also cover
how to prepare for a new DSA master.

The initial tagging protocol setup (at driver probe time) and the final
teardown (at driver removal time) are also adapted to call into the
structured methods of the specific protocol in current use. This is
especially relevant for teardown, where we previously called
felix_del_tag_protocol() only for the first CPU port. But by not
specifying which CPU port this is for, we gain more flexibility to
support multiple CPU ports in the future.
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/dsa/ocelot/felix.h

@@ -59,6 +59,19 @@ struct felix_info {
 				      struct resource *res);
 };
 
+/* Methods for initializing the hardware resources specific to a tagging
+ * protocol (like the NPI port, for "ocelot" or "seville", or the VCAP TCAMs,
+ * for "ocelot-8021q").
+ * It is important that the resources configured here do not have side effects
+ * for the other tagging protocols. If that is the case, their configuration
+ * needs to go to felix_tag_proto_setup_shared().
+ */
+struct felix_tag_proto_ops {
+	int (*setup)(struct dsa_switch *ds);
+	void (*teardown)(struct dsa_switch *ds);
+	unsigned long (*get_host_fwd_mask)(struct dsa_switch *ds);
+};
+
 extern const struct dsa_switch_ops felix_switch_ops;
 
 /* DSA glue / front-end for struct ocelot */
@@ -71,6 +84,7 @@ struct felix {
 	resource_size_t			switch_base;
 	resource_size_t			imdio_base;
 	enum dsa_tag_protocol		tag_proto;
+	const struct felix_tag_proto_ops *tag_proto_ops;
 	struct kthread_worker		*xmit_worker;
 	unsigned long			host_flood_uc_mask;
 	unsigned long			host_flood_mc_mask;