net: dsa: tag_sja1105: be dsa_loop-safe

Add support for tag_sja1105 running on non-sja1105 DSA ports, by making
sure that every time we dereference dp->priv, we check the switch's
dsa_switch_ops (otherwise we access a struct sja1105_port structure that
is in fact something else).

This adds an unconditional build-time dependency between sja1105 being
built as module => tag_sja1105 must also be built as module. This was
there only for PTP before.

Some sane defaults must also take place when not running on sja1105
hardware. These are:

- sja1105_xmit_tpid: the sja1105 driver uses different VLAN protocols
  depending on VLAN awareness and switch revision (when an encapsulated
  VLAN must be sent). Default to 0x8100.

- sja1105_rcv_meta_state_machine: this aggregates PTP frames with their
  metadata timestamp frames. When running on non-sja1105 hardware, don't
  do that and accept all frames unmodified.

- sja1105_defer_xmit: calls sja1105_port_deferred_xmit in sja1105_main.c
  which writes a management route over SPI. When not running on sja1105
  hardware, bypass the SPI write and send the frame as-is.
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/dsa/sja1105/sja1105_main.c

@@ -28,8 +28,6 @@
 #define SJA1105_UNKNOWN_MULTICAST	0x010000000000ull
 #define SJA1105_DEFAULT_VLAN		(VLAN_N_VID - 1)
 
-static const struct dsa_switch_ops sja1105_switch_ops;
-
 static void sja1105_hw_reset(struct gpio_desc *gpio, unsigned int pulse_len,
 			     unsigned int startup_delay)
 {
@@ -3100,7 +3098,7 @@ static void sja1105_teardown(struct dsa_switch *ds)
 	sja1105_static_config_free(&priv->static_config);
 }
 
-static const struct dsa_switch_ops sja1105_switch_ops = {
+const struct dsa_switch_ops sja1105_switch_ops = {
 	.get_tag_protocol	= sja1105_get_tag_protocol,
 	.setup			= sja1105_setup,
 	.teardown		= sja1105_teardown,
@@ -3149,6 +3147,7 @@ static const struct dsa_switch_ops sja1105_switch_ops = {
 	.port_bridge_tx_fwd_offload = dsa_tag_8021q_bridge_tx_fwd_offload,
 	.port_bridge_tx_fwd_unoffload = dsa_tag_8021q_bridge_tx_fwd_unoffload,
 };
+EXPORT_SYMBOL_GPL(sja1105_switch_ops);
 
 static const struct of_device_id sja1105_dt_ids[];
 

include/linux/dsa/sja1105.h

@@ -88,4 +88,22 @@ static inline void sja1110_process_meta_tstamp(struct dsa_switch *ds, int port,
 
 #endif /* IS_ENABLED(CONFIG_NET_DSA_SJA1105_PTP) */
 
+#if IS_ENABLED(CONFIG_NET_DSA_SJA1105)
+
+extern const struct dsa_switch_ops sja1105_switch_ops;
+
+static inline bool dsa_port_is_sja1105(struct dsa_port *dp)
+{
+	return dp->ds->ops == &sja1105_switch_ops;
+}
+
+#else
+
+static inline bool dsa_port_is_sja1105(struct dsa_port *dp)
+{
+	return false;
+}
+
+#endif
+
 #endif /* _NET_DSA_SJA1105_H */

net/dsa/Kconfig

@@ -138,7 +138,7 @@ config NET_DSA_TAG_LAN9303
 
 config NET_DSA_TAG_SJA1105
 	tristate "Tag driver for NXP SJA1105 switches"
-	depends on (NET_DSA_SJA1105 && NET_DSA_SJA1105_PTP) || !NET_DSA_SJA1105 || !NET_DSA_SJA1105_PTP
+	depends on NET_DSA_SJA1105 || !NET_DSA_SJA1105
 	select PACKING
 	help
 	  Say Y or M if you want to enable support for tagging frames with the

net/dsa/tag_sja1105.c

@@ -116,9 +116,14 @@ static inline bool sja1105_is_meta_frame(const struct sk_buff *skb)
 }
 
 /* Calls sja1105_port_deferred_xmit in sja1105_main.c */
-static struct sk_buff *sja1105_defer_xmit(struct sja1105_port *sp,
+static struct sk_buff *sja1105_defer_xmit(struct dsa_port *dp,
 					  struct sk_buff *skb)
 {
+	struct sja1105_port *sp = dp->priv;
+
+	if (!dsa_port_is_sja1105(dp))
+		return skb;
+
 	/* Increase refcount so the kfree_skb in dsa_slave_xmit
 	 * won't really free the packet.
 	 */
@@ -128,8 +133,13 @@ static struct sk_buff *sja1105_defer_xmit(struct sja1105_port *sp,
 	return NULL;
 }
 
-static u16 sja1105_xmit_tpid(struct sja1105_port *sp)
+static u16 sja1105_xmit_tpid(struct dsa_port *dp)
 {
+	struct sja1105_port *sp = dp->priv;
+
+	if (unlikely(!dsa_port_is_sja1105(dp)))
+		return ETH_P_8021Q;
+
 	return sp->xmit_tpid;
 }
 
@@ -155,7 +165,7 @@ static struct sk_buff *sja1105_imprecise_xmit(struct sk_buff *skb,
 	 */
 	tx_vid = dsa_8021q_bridge_tx_fwd_offload_vid(dp->bridge_num);
 
-	return dsa_8021q_xmit(skb, netdev, sja1105_xmit_tpid(dp->priv), tx_vid);
+	return dsa_8021q_xmit(skb, netdev, sja1105_xmit_tpid(dp), tx_vid);
 }
 
 static struct sk_buff *sja1105_xmit(struct sk_buff *skb,
@@ -174,9 +184,9 @@ static struct sk_buff *sja1105_xmit(struct sk_buff *skb,
 	 * is the .port_deferred_xmit driver callback.
 	 */
 	if (unlikely(sja1105_is_link_local(skb)))
-		return sja1105_defer_xmit(dp->priv, skb);
+		return sja1105_defer_xmit(dp, skb);
 
-	return dsa_8021q_xmit(skb, netdev, sja1105_xmit_tpid(dp->priv),
+	return dsa_8021q_xmit(skb, netdev, sja1105_xmit_tpid(dp),
 			     ((pcp << VLAN_PRIO_SHIFT) | tx_vid));
 }
 
@@ -200,7 +210,7 @@ static struct sk_buff *sja1110_xmit(struct sk_buff *skb,
 	 * tag_8021q TX VLANs.
 	 */
 	if (likely(!sja1105_is_link_local(skb)))
-		return dsa_8021q_xmit(skb, netdev, sja1105_xmit_tpid(dp->priv),
+		return dsa_8021q_xmit(skb, netdev, sja1105_xmit_tpid(dp),
 				     ((pcp << VLAN_PRIO_SHIFT) | tx_vid));
 
 	skb_push(skb, SJA1110_HEADER_LEN);
@@ -265,16 +275,16 @@ static struct sk_buff
 				bool is_link_local,
 				bool is_meta)
 {
-	struct sja1105_port *sp;
-	struct dsa_port *dp;
-
-	dp = dsa_slave_to_port(skb->dev);
-	sp = dp->priv;
-
 	/* Step 1: A timestampable frame was received.
 	 * Buffer it until we get its meta frame.
 	 */
 	if (is_link_local) {
+		struct dsa_port *dp = dsa_slave_to_port(skb->dev);
+		struct sja1105_port *sp = dp->priv;
+
+		if (unlikely(!dsa_port_is_sja1105(dp)))
+			return skb;
+
 		if (!test_bit(SJA1105_HWTS_RX_EN, &sp->data->state))
 			/* Do normal processing. */
 			return skb;
@@ -307,8 +317,13 @@ static struct sk_buff
 	 * frame, which serves no further purpose).
 	 */
 	} else if (is_meta) {
+		struct dsa_port *dp = dsa_slave_to_port(skb->dev);
+		struct sja1105_port *sp = dp->priv;
 		struct sk_buff *stampable_skb;
 
+		if (unlikely(!dsa_port_is_sja1105(dp)))
+			return skb;
+
 		/* Drop the meta frame if we're not in the right state
 		 * to process it.
 		 */