net: dsa: keep the bridge_dev and bridge_num as part of the same structure

The main desire behind this is to provide coherent bridge information to
the fast path without locking.

For example, right now we set dp->bridge_dev and dp->bridge_num from
separate code paths, it is theoretically possible for a packet
transmission to read these two port properties consecutively and find a
bridge number which does not correspond with the bridge device.

Another desire is to start passing more complex bridge information to
dsa_switch_ops functions. For example, with FDB isolation, it is
expected that drivers will need to be passed the bridge which requested
an FDB/MDB entry to be offloaded, and along with that bridge_dev, the
associated bridge_num should be passed too, in case the driver might
want to implement an isolation scheme based on that number.

We already pass the {bridge_dev, bridge_num} pair to the TX forwarding
offload switch API, however we'd like to remove that and squash it into
the basic bridge join/leave API. So that means we need to pass this
pair to the bridge join/leave API.

During dsa_port_bridge_leave, first we unset dp->bridge_dev, then we
call the driver's .port_bridge_leave with what used to be our
dp->bridge_dev, but provided as an argument.

When bridge_dev and bridge_num get folded into a single structure, we
need to preserve this behavior in dsa_port_bridge_leave: we need a copy
of what used to be in dp->bridge.

Switch drivers check bridge membership by comparing dp->bridge_dev with
the provided bridge_dev, but now, if we provide the struct dsa_bridge as
a pointer, they cannot keep comparing dp->bridge to the provided
pointer, since this only points to an on-stack copy. To make this
obvious and prevent driver writers from forgetting and doing stupid
things, in this new API, the struct dsa_bridge is provided as a full
structure (not very large, contains an int and a pointer) instead of a
pointer. An explicit comparison function needs to be used to determine
bridge membership: dsa_port_offloads_bridge().

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Alvin Šipraga <alsi@bang-olufsen.dk>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

2 files changed, 4 insertions, 4 deletions

diff --git a/drivers/net/dsa/microchip/ksz_common.c b/drivers/net/dsa/microchip/ksz_common.c
index cebcb73cda76..40d6e3f4deb5 100644
--- a/drivers/net/dsa/microchip/ksz_common.c
+++ b/drivers/net/dsa/microchip/ksz_common.c
@@ -192,7 +192,7 @@ void ksz_get_ethtool_stats(struct dsa_switch *ds, int port, uint64_t *buf)
 EXPORT_SYMBOL_GPL(ksz_get_ethtool_stats);
 
 int ksz_port_bridge_join(struct dsa_switch *ds, int port,
-			 struct net_device *br)
+			 struct dsa_bridge bridge)
 {
 	/* port_stp_state_set() will be called after to put the port in
 	 * appropriate state so there is no need to do anything.
@@ -203,7 +203,7 @@ int ksz_port_bridge_join(struct dsa_switch *ds, int port,
 EXPORT_SYMBOL_GPL(ksz_port_bridge_join);
 
 void ksz_port_bridge_leave(struct dsa_switch *ds, int port,
-			   struct net_device *br)
+			   struct dsa_bridge bridge)
 {
 	/* port_stp_state_set() will be called after to put the port in
 	 * forwarding state so there is no need to do anything.
diff --git a/drivers/net/dsa/microchip/ksz_common.h b/drivers/net/dsa/microchip/ksz_common.h
index 54b456bc8972..88e5a5d56219 100644
--- a/drivers/net/dsa/microchip/ksz_common.h
+++ b/drivers/net/dsa/microchip/ksz_common.h
@@ -155,9 +155,9 @@ void ksz_mac_link_down(struct dsa_switch *ds, int port, unsigned int mode,
 int ksz_sset_count(struct dsa_switch *ds, int port, int sset);
 void ksz_get_ethtool_stats(struct dsa_switch *ds, int port, uint64_t *buf);
 int ksz_port_bridge_join(struct dsa_switch *ds, int port,
-			 struct net_device *br);
+			 struct dsa_bridge bridge);
 void ksz_port_bridge_leave(struct dsa_switch *ds, int port,
-			   struct net_device *br);
+			   struct dsa_bridge bridge);
 void ksz_port_fast_age(struct dsa_switch *ds, int port);
 int ksz_port_fdb_dump(struct dsa_switch *ds, int port, dsa_fdb_dump_cb_t *cb,
 		      void *data);