net: dsa: remove the "dsa_to_port in a loop" antipattern from the core

Ever since Vivien's conversion of the ds->ports array into a dst->ports
list, and the introduction of dsa_to_port, iterations through the ports
of a switch became quadratic whenever dsa_to_port was needed.

dsa_to_port can either be called directly, or indirectly through the
dsa_is_{user,cpu,dsa,unused}_port helpers.

Use the newly introduced dsa_switch_for_each_port() iteration macro
that works with the iterator variable being a struct dsa_port *dp
directly, and not an int i. It is an expensive variable to go from i to
dp, but cheap to go from dp to i.

This macro iterates through the entire ds->dst->ports list and filters
by the ports belonging just to the switch provided as argument.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 3 insertions, 4 deletions

diff --git a/include/net/dsa.h b/include/net/dsa.h
index 440b6aca22c7..1cd9c2461f0d 100644
--- a/include/net/dsa.h
+++ b/include/net/dsa.h
@@ -504,12 +504,11 @@ static inline bool dsa_is_user_port(struct dsa_switch *ds, int p)
 
 static inline u32 dsa_user_ports(struct dsa_switch *ds)
 {
+	struct dsa_port *dp;
 	u32 mask = 0;
-	int p;
 
-	for (p = 0; p < ds->num_ports; p++)
-		if (dsa_is_user_port(ds, p))
-			mask |= BIT(p);
+	dsa_switch_for_each_user_port(dp, ds)
+		mask |= BIT(dp->index);
 
 	return mask;
 }