net/mlx5: SD, Handle possible devcom ERR_PTR

Check if devcom holds an error pointer and return immediately.

This fixes Smatch static checker warning:
drivers/net/ethernet/mellanox/mlx5/core/lib/sd.c:221 sd_register()
error: 'devcom' dereferencing possible ERR_PTR()

Enhance mlx5_devcom_register_component() so it stops returning NULL,
making it easier for its callers.

Fixes: d3d0576 ("net/mlx5: SD, Implement devcom communication and primary election")
Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Link: https://lore.kernel.org/all/f09666c8-e604-41f6-958b-4cc55c73faf9@gmail.com/T/
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Reviewed-by: Gal Pressman <gal@nvidia.com>
Link: https://lore.kernel.org/r/20240411115444.374475-3-tariqt@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: Tariq Toukan

drivers/net/ethernet/mellanox/mlx5/core/en_main.c

@@ -209,8 +209,8 @@ static int mlx5e_devcom_init_mpv(struct mlx5e_priv *priv, u64 *data)
 						      *data,
 						      mlx5e_devcom_event_mpv,
 						      priv);
-	if (IS_ERR_OR_NULL(priv->devcom))
-		return -EOPNOTSUPP;
+	if (IS_ERR(priv->devcom))
+		return PTR_ERR(priv->devcom);
 
 	if (mlx5_core_is_mp_master(priv->mdev)) {
 		mlx5_devcom_send_event(priv->devcom, MPV_DEVCOM_MASTER_UP,

drivers/net/ethernet/mellanox/mlx5/core/eswitch_offloads.c

@@ -3060,7 +3060,7 @@ void mlx5_esw_offloads_devcom_init(struct mlx5_eswitch *esw, u64 key)
 						     key,
 						     mlx5_esw_offloads_devcom_event,
 						     esw);
-	if (IS_ERR_OR_NULL(esw->devcom))
+	if (IS_ERR(esw->devcom))
 		return;
 
 	mlx5_devcom_send_event(esw->devcom,

drivers/net/ethernet/mellanox/mlx5/core/lib/devcom.c

@@ -220,7 +220,7 @@ mlx5_devcom_register_component(struct mlx5_devcom_dev *devc,
 	struct mlx5_devcom_comp *comp;
 
 	if (IS_ERR_OR_NULL(devc))
-		return NULL;
+		return ERR_PTR(-EINVAL);
 
 	mutex_lock(&comp_list_lock);
 	comp = devcom_component_get(devc, id, key, handler);

drivers/net/ethernet/mellanox/mlx5/core/lib/sd.c

@@ -213,8 +213,8 @@ static int sd_register(struct mlx5_core_dev *dev)
 	sd = mlx5_get_sd(dev);
 	devcom = mlx5_devcom_register_component(dev->priv.devc, MLX5_DEVCOM_SD_GROUP,
 						sd->group_id, NULL, dev);
-	if (!devcom)
-		return -ENOMEM;
+	if (IS_ERR(devcom))
+		return PTR_ERR(devcom);
 
 	sd->devcom = devcom;
 

drivers/net/ethernet/mellanox/mlx5/core/main.c

@@ -956,7 +956,7 @@ static void mlx5_register_hca_devcom_comp(struct mlx5_core_dev *dev)
 		mlx5_devcom_register_component(dev->priv.devc, MLX5_DEVCOM_HCA_PORTS,
 					       mlx5_query_nic_system_image_guid(dev),
 					       NULL, dev);
-	if (IS_ERR_OR_NULL(dev->priv.hca_devcom_comp))
+	if (IS_ERR(dev->priv.hca_devcom_comp))
 		mlx5_core_err(dev, "Failed to register devcom HCA component\n");
 }