net: dsa: provide a second modalias to tag proto drivers based on their name

Currently, tagging protocol drivers have a modalias of
"dsa_tag:id-<number>", where the number is one of DSA_TAG_PROTO_*_VALUE.

This modalias makes it possible for the request_module() call in
dsa_tag_driver_get() to work, given the input it has - an integer
returned by ds->ops->get_tag_protocol().

It is also possible to change tagging protocols at (pseudo-)runtime, via
sysfs or via device tree, and this works via the name string of the
tagging protocol rather than via its id (DSA_TAG_PROTO_*_VALUE).

In the latter case, there is no request_module() call, because there is
no association that the DSA core has between the string name and the ID,
to construct the modalias. The module is simply assumed to have been
inserted. This is actually slightly problematic when the tagging
protocol change should take place at probe time, since it's expected
that the dependency module should get autoloaded.

For this purpose, let's introduce a second modalias, so that the DSA
core can call request_module() by name. There is no reason to make the
modalias by name optional, so just modify the MODULE_ALIAS_DSA_TAG_DRIVER()
macro to take both the ID and the name as arguments, and generate two
modaliases behind the scenes.

Suggested-by: Michael Walle <michael@walle.cc>
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Tested-by: Michael Walle <michael@walle.cc> # on kontron-sl28 w/ ocelot_8021q
Tested-by: Michael Walle <michael@walle.cc>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 13 insertions, 8 deletions

diff --git a/net/dsa/tag_ksz.c b/net/dsa/tag_ksz.c
index 38fa19c1e2d5..37db5156f9a3 100644
--- a/net/dsa/tag_ksz.c
+++ b/net/dsa/tag_ksz.c
@@ -9,6 +9,11 @@
 #include <net/dsa.h>
 #include "dsa_priv.h"
 
+#define KSZ8795_NAME "ksz8795"
+#define KSZ9477_NAME "ksz9477"
+#define KSZ9893_NAME "ksz9893"
+#define LAN937X_NAME "lan937x"
+
 /* Typically only one byte is used for tail tag. */
 #define KSZ_EGRESS_TAG_LEN		1
 #define KSZ_INGRESS_TAG_LEN		1
@@ -74,7 +79,7 @@ static struct sk_buff *ksz8795_rcv(struct sk_buff *skb, struct net_device *dev)
 }
 
 static const struct dsa_device_ops ksz8795_netdev_ops = {
-	.name	= "ksz8795",
+	.name	= KSZ8795_NAME,
 	.proto	= DSA_TAG_PROTO_KSZ8795,
 	.xmit	= ksz8795_xmit,
 	.rcv	= ksz8795_rcv,
@@ -82,7 +87,7 @@ static const struct dsa_device_ops ksz8795_netdev_ops = {
 };
 
 DSA_TAG_DRIVER(ksz8795_netdev_ops);
-MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_KSZ8795);
+MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_KSZ8795, KSZ8795_NAME);
 
 /*
  * For Ingress (Host -> KSZ9477), 2 bytes are added before FCS.
@@ -147,7 +152,7 @@ static struct sk_buff *ksz9477_rcv(struct sk_buff *skb, struct net_device *dev)
 }
 
 static const struct dsa_device_ops ksz9477_netdev_ops = {
-	.name	= "ksz9477",
+	.name	= KSZ9477_NAME,
 	.proto	= DSA_TAG_PROTO_KSZ9477,
 	.xmit	= ksz9477_xmit,
 	.rcv	= ksz9477_rcv,
@@ -155,7 +160,7 @@ static const struct dsa_device_ops ksz9477_netdev_ops = {
 };
 
 DSA_TAG_DRIVER(ksz9477_netdev_ops);
-MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_KSZ9477);
+MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_KSZ9477, KSZ9477_NAME);
 
 #define KSZ9893_TAIL_TAG_OVERRIDE	BIT(5)
 #define KSZ9893_TAIL_TAG_LOOKUP		BIT(6)
@@ -183,7 +188,7 @@ static struct sk_buff *ksz9893_xmit(struct sk_buff *skb,
 }
 
 static const struct dsa_device_ops ksz9893_netdev_ops = {
-	.name	= "ksz9893",
+	.name	= KSZ9893_NAME,
 	.proto	= DSA_TAG_PROTO_KSZ9893,
 	.xmit	= ksz9893_xmit,
 	.rcv	= ksz9477_rcv,
@@ -191,7 +196,7 @@ static const struct dsa_device_ops ksz9893_netdev_ops = {
 };
 
 DSA_TAG_DRIVER(ksz9893_netdev_ops);
-MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_KSZ9893);
+MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_KSZ9893, KSZ9893_NAME);
 
 /* For xmit, 2 bytes are added before FCS.
  * ---------------------------------------------------------------------------
@@ -241,7 +246,7 @@ static struct sk_buff *lan937x_xmit(struct sk_buff *skb,
 }
 
 static const struct dsa_device_ops lan937x_netdev_ops = {
-	.name	= "lan937x",
+	.name	= LAN937X_NAME,
 	.proto	= DSA_TAG_PROTO_LAN937X,
 	.xmit	= lan937x_xmit,
 	.rcv	= ksz9477_rcv,
@@ -249,7 +254,7 @@ static const struct dsa_device_ops lan937x_netdev_ops = {
 };
 
 DSA_TAG_DRIVER(lan937x_netdev_ops);
-MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_LAN937X);
+MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_LAN937X, LAN937X_NAME);
 
 static struct dsa_tag_driver *dsa_tag_driver_array[] = {
 	&DSA_TAG_DRIVER_NAME(ksz8795_netdev_ops),