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, 9 insertions, 9 deletions

diff --git a/include/linux/dsa/8021q.h b/include/linux/dsa/8021q.h
index 9945898a90c3..77939c0c8dd5 100644
--- a/include/linux/dsa/8021q.h
+++ b/include/linux/dsa/8021q.h
@@ -34,20 +34,20 @@ struct dsa_8021q_context {
 	__be16 proto;
 };
 
-struct dsa_8021q_context *dsa_tag_8021q_register(struct dsa_switch *ds,
-						 const struct dsa_8021q_ops *ops,
-						 __be16 proto);
+int dsa_tag_8021q_register(struct dsa_switch *ds,
+			   const struct dsa_8021q_ops *ops,
+			   __be16 proto);
 
-void dsa_tag_8021q_unregister(struct dsa_8021q_context *ctx);
+void dsa_tag_8021q_unregister(struct dsa_switch *ds);
 
-int dsa_8021q_setup(struct dsa_8021q_context *ctx, bool enabled);
+int dsa_8021q_setup(struct dsa_switch *ds, bool enabled);
 
-int dsa_8021q_crosschip_bridge_join(struct dsa_8021q_context *ctx, int port,
-				    struct dsa_8021q_context *other_ctx,
+int dsa_8021q_crosschip_bridge_join(struct dsa_switch *ds, int port,
+				    struct dsa_switch *other_ds,
 				    int other_port);
 
-int dsa_8021q_crosschip_bridge_leave(struct dsa_8021q_context *ctx, int port,
-				     struct dsa_8021q_context *other_ctx,
+int dsa_8021q_crosschip_bridge_leave(struct dsa_switch *ds, int port,
+				     struct dsa_switch *other_ds,
 				     int other_port);
 
 struct sk_buff *dsa_8021q_xmit(struct sk_buff *skb, struct net_device *netdev,