Re: [PATCH net] net/mlx4: always create the eth and ib auxiliary devices

[Simon Horman <horms@kernel.org>]

On Tue, Oct 20, 2026 at 05:42:39PM +0100, Peter Morrow wrote:
> Since commit 7d22b1cb9d84 ("mlx4: Connect the infiniband part to the
> auxiliary bus"), mlx4_core creates the "ib" auxiliary device only for
> an IB port or a device that advertises IBoE. Before it, each mlx4
> interface was offered every device and decided in its own add callback.
> mlx4_ib_add() accepted Ethernet ports without IBoE and registered them
> for raw packet QPs only.
> 
> ConnectX-3 VFs on Azure have an Ethernet port and no IBoE, so since
> v6.6 they get no RDMA device. DPDK's mlx4 PMD, which needs only raw
> packet QPs, then cannot open them:
> 
>   net_mlx4: cannot access device, is mlx4_ib loaded?
> 
> Restore the old behaviour by creating both auxiliary devices for every
> device and letting mlx4_en and mlx4_ib decide in probe, as their add
> callbacks did. mlx4_ib_probe() returns -ENODEV when there are no usable
> ports, and mlx4_en_probe() binds a device without Ethernet ports but
> creates no netdevs, as mlx4_en_add() did.
> 
> Tested on 6.12.111 on an Azure VM with two ConnectX-3 VFs: each gets an
> eth and an ib auxiliary device, and DPDK attaches both VFs and passes
> traffic through them.
> 
> Fixes: 7d22b1cb9d84 ("mlx4: Connect the infiniband part to the auxiliary bus")
> Closes: https://lore.kernel.org/r/20261014133951.3219055-1-pdmorrow@gmail.com
> Suggested-by: Leon Romanovsky <leon@kernel.org>
> Assisted-by: LLM
> Signed-off-by: Peter Morrow <pdmorrow@gmail.com>

Thanks, this looks good to me.
And I think the minimal approach taken here is appropriate for net.

Reviewed-by: Simon Horman <horms@kernel.org>

I do, however, wonder if a follow-up is warranted.
It seems to me that the is_supported callback could
be removed entirely. Leaving either:
1. struct mlx4_adev_device with a single member, .suffix
2. mlx4_adev_devices as an array of of strings

To explore this idea a little further I tried coding-up approach 2.
Which lead to the following (compile tested only):

diff --git a/drivers/net/ethernet/mellanox/mlx4/intf.c b/drivers/net/ethernet/mellanox/mlx4/intf.c
index 82e467c45d23..f2f35306aeb3 100644
--- a/drivers/net/ethernet/mellanox/mlx4/intf.c
+++ b/drivers/net/ethernet/mellanox/mlx4/intf.c
@@ -41,34 +41,7 @@
 static DEFINE_MUTEX(intf_mutex);
 static DEFINE_IDA(mlx4_adev_ida);
 
-static bool is_eth_supported(struct mlx4_dev *dev)
-{
-	for (int port = 1; port <= dev->caps.num_ports; port++)
-		if (dev->caps.port_type[port] == MLX4_PORT_TYPE_ETH)
-			return true;
-
-	return false;
-}
-
-static bool is_ib_supported(struct mlx4_dev *dev)
-{
-	for (int port = 1; port <= dev->caps.num_ports; port++)
-		if (dev->caps.port_type[port] == MLX4_PORT_TYPE_IB)
-			return true;
-
-	if (dev->caps.flags & MLX4_DEV_CAP_FLAG_IBOE)
-		return true;
-
-	return false;
-}
-
-static const struct mlx4_adev_device {
-	const char *suffix;
-	bool (*is_supported)(struct mlx4_dev *dev);
-} mlx4_adev_devices[] = {
-	{ "eth", is_eth_supported },
-	{ "ib", is_ib_supported },
-};
+static const char * const mlx4_adev_devices[] = { "eth", "ib" };
 
 int mlx4_adev_init(struct mlx4_dev *dev)
 {
@@ -109,8 +82,8 @@ static void adev_release(struct device *dev)
 
 static struct mlx4_adev *add_adev(struct mlx4_dev *dev, int idx)
 {
+	const char *suffix = mlx4_adev_devices[idx];
 	struct mlx4_priv *priv = mlx4_priv(dev);
-	const char *suffix = mlx4_adev_devices[idx].suffix;
 	struct auxiliary_device *adev;
 	struct mlx4_adev *madev;
 	int ret;
@@ -222,7 +195,7 @@ int mlx4_do_bond(struct mlx4_dev *dev, bool enable)
 		priv->adev[i] = add_adev(dev, i);
 		if (IS_ERR(priv->adev[i])) {
 			mlx4_warn(dev, "Device[%d] (%s) failed to load\n", i,
-				  mlx4_adev_devices[i].suffix);
+				  mlx4_adev_devices[i]);
 			priv->adev[i] = NULL;
 			continue;
 		}
@@ -269,21 +242,13 @@ static int add_drivers(struct mlx4_dev *dev)
 	int i, ret = 0;
 
 	for (i = 0; i < ARRAY_SIZE(mlx4_adev_devices); i++) {
-		bool is_supported = false;
-
 		if (priv->adev[i])
 			continue;
 
-		if (mlx4_adev_devices[i].is_supported)
-			is_supported = mlx4_adev_devices[i].is_supported(dev);
-
-		if (!is_supported)
-			continue;
-
 		priv->adev[i] = add_adev(dev, i);
 		if (IS_ERR(priv->adev[i])) {
 			mlx4_warn(dev, "Device[%d] (%s) failed to load\n", i,
-				  mlx4_adev_devices[i].suffix);
+				  mlx4_adev_devices[i]);
 			/* We continue to rescan drivers and leave to the caller
 			 * to make decision if to release everything or
 			 * continue. */
@@ -297,23 +262,15 @@ static int add_drivers(struct mlx4_dev *dev)
 static void delete_drivers(struct mlx4_dev *dev)
 {
 	struct mlx4_priv *priv = mlx4_priv(dev);
-	bool delete_all;
 	int i;
 
-	delete_all = !(dev->persist->interface_state & MLX4_INTERFACE_STATE_UP);
+	if (dev->persist->interface_state & MLX4_INTERFACE_STATE_UP)
+		return;
 
 	for (i = ARRAY_SIZE(mlx4_adev_devices) - 1; i >= 0; i--) {
-		bool is_supported = false;
-
 		if (!priv->adev[i])
 			continue;
 
-		if (mlx4_adev_devices[i].is_supported && !delete_all)
-			is_supported = mlx4_adev_devices[i].is_supported(dev);
-
-		if (is_supported)
-			continue;
-
 		del_adev(&priv->adev[i]->adev);
 		priv->adev[i] = NULL;
 	}