net: dsa: tag_8021q: add helpers to deduce whether a VLAN ID is RX or TX VLAN

The sja1105 implementation can be blind about this, but the felix driver
doesn't do exactly what it's being told, so it needs to know whether it
is a TX or an RX VLAN, so it can install the appropriate type of TCAM
rule.
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

include/linux/dsa/8021q.h

@@ -64,6 +64,10 @@ int dsa_8021q_rx_source_port(u16 vid);
 
 u16 dsa_8021q_rx_subvlan(u16 vid);
 
+bool vid_is_dsa_8021q_rxvlan(u16 vid);
+
+bool vid_is_dsa_8021q_txvlan(u16 vid);
+
 bool vid_is_dsa_8021q(u16 vid);
 
 #else
@@ -123,6 +127,16 @@ u16 dsa_8021q_rx_subvlan(u16 vid)
 	return 0;
 }
 
+bool vid_is_dsa_8021q_rxvlan(u16 vid)
+{
+	return false;
+}
+
+bool vid_is_dsa_8021q_txvlan(u16 vid)
+{
+	return false;
+}
+
 bool vid_is_dsa_8021q(u16 vid)
 {
 	return false;

net/dsa/tag_8021q.c

@@ -133,10 +133,21 @@ u16 dsa_8021q_rx_subvlan(u16 vid)
 }
 EXPORT_SYMBOL_GPL(dsa_8021q_rx_subvlan);
 
+bool vid_is_dsa_8021q_rxvlan(u16 vid)
+{
+	return (vid & DSA_8021Q_DIR_MASK) == DSA_8021Q_DIR_RX;
+}
+EXPORT_SYMBOL_GPL(vid_is_dsa_8021q_rxvlan);
+
+bool vid_is_dsa_8021q_txvlan(u16 vid)
+{
+	return (vid & DSA_8021Q_DIR_MASK) == DSA_8021Q_DIR_TX;
+}
+EXPORT_SYMBOL_GPL(vid_is_dsa_8021q_txvlan);
+
 bool vid_is_dsa_8021q(u16 vid)
 {
-	return ((vid & DSA_8021Q_DIR_MASK) == DSA_8021Q_DIR_RX ||
-		(vid & DSA_8021Q_DIR_MASK) == DSA_8021Q_DIR_TX);
+	return vid_is_dsa_8021q_rxvlan(vid) || vid_is_dsa_8021q_txvlan(vid);
 }
 EXPORT_SYMBOL_GPL(vid_is_dsa_8021q);