net: dsa: let the core manage the tag_8021q context

The basic problem description is as follows:

Be there 3 switches in a daisy chain topology:

                                             |
    sw0p0     sw0p1     sw0p2     sw0p3     sw0p4
 [  user ] [  user ] [  user ] [  dsa  ] [  cpu  ]
                                   |
                                   +---------+
                                             |
    sw1p0     sw1p1     sw1p2     sw1p3     sw1p4
 [  user ] [  user ] [  user ] [  dsa  ] [  dsa  ]
                                   |
                                   +---------+
                                             |
    sw2p0     sw2p1     sw2p2     sw2p3     sw2p4
 [  user ] [  user ] [  user ] [  user ] [  dsa  ]

The CPU will not be able to ping through the user ports of the
bottom-most switch (like for example sw2p0), simply because tag_8021q
was not coded up for this scenario - it has always assumed DSA switch
trees with a single switch.

To add support for the topology above, we must admit that the RX VLAN of
sw2p0 must be added on some ports of switches 0 and 1 as well. This is
in fact a textbook example of thing that can use the cross-chip notifier
framework that DSA has set up in switch.c.

There is only one problem: core DSA (switch.c) is not able right now to
make the connection between a struct dsa_switch *ds and a struct
dsa_8021q_context *ctx. Right now, it is drivers who call into
tag_8021q.c and always provide a struct dsa_8021q_context *ctx pointer,
and tag_8021q.c calls them back with the .tag_8021q_vlan_{add,del}
methods.

But with cross-chip notifiers, it is possible for tag_8021q to call
drivers without drivers having ever asked for anything. A good example
is right above: when sw2p0 wants to set itself up for tag_8021q,
the .tag_8021q_vlan_add method needs to be called for switches 1 and 0,
so that they transport sw2p0's VLANs towards the CPU without dropping
them.

So instead of letting drivers manage the tag_8021q context, add a
tag_8021q_ctx pointer inside of struct dsa_switch, which will be
populated when dsa_tag_8021q_register() returns success.

The patch is fairly long-winded because we are partly reverting commit
5899ee367ab3 ("net: dsa: tag_8021q: add a context structure") which made
the driver-facing tag_8021q API use "ctx" instead of "ds". Now that we
can access "ctx" directly from "ds", this is no longer needed.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 11 insertions, 11 deletions

diff --git a/drivers/net/dsa/ocelot/felix.c b/drivers/net/dsa/ocelot/felix.c
index b52cc381cdc1..9e4ae15aa4fb 100644
--- a/drivers/net/dsa/ocelot/felix.c
+++ b/drivers/net/dsa/ocelot/felix.c
@@ -425,14 +425,14 @@ static int felix_setup_tag_8021q(struct dsa_switch *ds, int cpu)
 	ocelot_rmw_rix(ocelot, 0, cpu_flood, ANA_PGID_PGID, PGID_MC);
 	ocelot_rmw_rix(ocelot, 0, cpu_flood, ANA_PGID_PGID, PGID_BC);
 
-	felix->dsa_8021q_ctx = dsa_tag_8021q_register(ds, &felix_tag_8021q_ops,
-						      htons(ETH_P_8021AD));
-	if (!felix->dsa_8021q_ctx)
-		return -ENOMEM;
+	err = dsa_tag_8021q_register(ds, &felix_tag_8021q_ops,
+				     htons(ETH_P_8021AD));
+	if (err)
+		return err;
 
-	err = dsa_8021q_setup(felix->dsa_8021q_ctx, true);
+	err = dsa_8021q_setup(ds, true);
 	if (err)
-		goto out_free_dsa_8021_ctx;
+		goto out_tag_8021q_unregister;
 
 	err = felix_setup_mmio_filtering(felix);
 	if (err)
@@ -441,9 +441,9 @@ static int felix_setup_tag_8021q(struct dsa_switch *ds, int cpu)
 	return 0;
 
 out_teardown_dsa_8021q:
-	dsa_8021q_setup(felix->dsa_8021q_ctx, false);
-out_free_dsa_8021_ctx:
-	dsa_tag_8021q_unregister(felix->dsa_8021q_ctx);
+	dsa_8021q_setup(ds, false);
+out_tag_8021q_unregister:
+	dsa_tag_8021q_unregister(ds);
 	return err;
 }
 
@@ -458,11 +458,11 @@ static void felix_teardown_tag_8021q(struct dsa_switch *ds, int cpu)
 		dev_err(ds->dev, "felix_teardown_mmio_filtering returned %d",
 			err);
 
-	err = dsa_8021q_setup(felix->dsa_8021q_ctx, false);
+	err = dsa_8021q_setup(ds, false);
 	if (err)
 		dev_err(ds->dev, "dsa_8021q_setup returned %d", err);
 
-	dsa_tag_8021q_unregister(felix->dsa_8021q_ctx);
+	dsa_tag_8021q_unregister(ds);
 
 	for (port = 0; port < ds->num_ports; port++) {
 		if (dsa_is_unused_port(ds, port))