[RFC PATCH v2 net-next 10/15] net: dsa: Pass ndo_setup_tc slave callback to drivers

[Vladimir Oltean <olteanv@gmail.com>]

DSA currently handles shared block filters (for the classifier-action
qdisc) in the core due to what I believe are simply pragmatic reasons -
hiding the complexity from drivers and offerring a simple API for port
mirroring.

Extend the dsa_slave_setup_tc function by passing all other qdisc
offloads to the driver layer, where the driver may choose what it
implements and how. DSA is simply a pass-through in this case.

There is an open question related to the drivers potentially needing to
do work in process context, but .ndo_setup_tc is called in atomic
context. At the moment the drivers are left to handle this on their own.
The risk is that once accepting the offload callback right away in the
DSA core, then the driver would have no way to signal an error back. So
right now the driver has to do as much error checking as possible in the
atomic context and only defer (probably) the actual configuring of the
offload.

Signed-off-by: Vladimir Oltean <olteanv@gmail.com>
---
 include/net/dsa.h |  3 +++
 net/dsa/slave.c   | 12 ++++++++----
 2 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/include/net/dsa.h b/include/net/dsa.h
index 96acb14ec1a8..232b5d36815d 100644
--- a/include/net/dsa.h
+++ b/include/net/dsa.h
@@ -154,6 +154,7 @@ struct dsa_mall_tc_entry {
 	};
 };
 
+struct tc_taprio_qopt_offload;
 
 struct dsa_port {
 	/* A CPU port is physically connected to a master device.
@@ -515,6 +516,8 @@ struct dsa_switch_ops {
 				   bool ingress);
 	void	(*port_mirror_del)(struct dsa_switch *ds, int port,
 				   struct dsa_mall_mirror_tc_entry *mirror);
+	int	(*port_setup_tc)(struct dsa_switch *ds, int port,
+				 enum tc_setup_type type, void *type_data);
 
 	/*
 	 * Cross-chip operations
diff --git a/net/dsa/slave.c b/net/dsa/slave.c
index 9a88035517a6..75d58229a4bd 100644
--- a/net/dsa/slave.c
+++ b/net/dsa/slave.c
@@ -1035,12 +1035,16 @@ static int dsa_slave_setup_tc_block(struct net_device *dev,
 static int dsa_slave_setup_tc(struct net_device *dev, enum tc_setup_type type,
 			      void *type_data)
 {
-	switch (type) {
-	case TC_SETUP_BLOCK:
+	struct dsa_port *dp = dsa_slave_to_port(dev);
+	struct dsa_switch *ds = dp->ds;
+
+	if (type == TC_SETUP_BLOCK)
 		return dsa_slave_setup_tc_block(dev, type_data);
-	default:
+
+	if (!ds->ops->port_setup_tc)
 		return -EOPNOTSUPP;
-	}
+
+	return ds->ops->port_setup_tc(ds, dp->index, type, type_data);
 }
 
 static void dsa_slave_get_stats64(struct net_device *dev,
-- 
2.17.1