[PATCH v2] net: dsa: use more appropriate NET_NAME_* constants for user ports

[Rasmus Villemoes <linux@rasmusvillemoes.dk>]

When a user port has a label in device tree, the corresponding
netdevice is "predictably named by the kernel".

Expose that information properly for the benefit of userspace tools
that make decisions based on the name_assign_type attribute,
e.g. a systemd-udev rule with "kernel" in NamePolicy.

Similarly, when we fall back to the eth%d scheme, the proper constant
to use is NET_NAME_ENUM. See also commit e9f656b7a214 ("net: ethernet:
set default assignment identifier to NET_NAME_ENUM"), which in turn
quoted commit 685343fc3ba6 ("net: add name_assign_type netdev
attribute"):

    ... when the kernel has given the interface a name using global
    device enumeration based on order of discovery (ethX, wlanY, etc)
    ... are labelled NET_NAME_ENUM.

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
---

v2: switch to NET_NAME_ENUM in the eth%d case (Andrew, Jakub). Update
commit message accordingly.

 net/dsa/dsa2.c  |  3 ---
 net/dsa/slave.c | 13 +++++++++++--
 2 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/net/dsa/dsa2.c b/net/dsa/dsa2.c
index e504a18fc125..522fc1b6e8c6 100644
--- a/net/dsa/dsa2.c
+++ b/net/dsa/dsa2.c
@@ -1364,9 +1364,6 @@ static struct dsa_port *dsa_port_touch(struct dsa_switch *ds, int index)
 
 static int dsa_port_parse_user(struct dsa_port *dp, const char *name)
 {
-	if (!name)
-		name = "eth%d";
-
 	dp->type = DSA_PORT_TYPE_USER;
 	dp->name = name;
 
diff --git a/net/dsa/slave.c b/net/dsa/slave.c
index a9fde48cffd4..821ab79bb60a 100644
--- a/net/dsa/slave.c
+++ b/net/dsa/slave.c
@@ -2374,16 +2374,25 @@ int dsa_slave_create(struct dsa_port *port)
 {
 	struct net_device *master = dsa_port_to_master(port);
 	struct dsa_switch *ds = port->ds;
-	const char *name = port->name;
 	struct net_device *slave_dev;
 	struct dsa_slave_priv *p;
+	const char *name;
+	int assign_type;
 	int ret;
 
 	if (!ds->num_tx_queues)
 		ds->num_tx_queues = 1;
 
+	if (port->name) {
+		name = port->name;
+		assign_type = NET_NAME_PREDICTABLE;
+	} else {
+		name = "eth%d";
+		assign_type = NET_NAME_ENUM;
+	}
+
 	slave_dev = alloc_netdev_mqs(sizeof(struct dsa_slave_priv), name,
-				     NET_NAME_UNKNOWN, ether_setup,
+				     assign_type, ether_setup,
 				     ds->num_tx_queues, 1);
 	if (slave_dev == NULL)
 		return -ENOMEM;
-- 
2.37.2