---
name: "mlx5dv_query_port"
section: "3"
platform: "linux"
package: "rdma-core"
version: "65.0-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/mlx5dv_query_port"
---

# mlx5dv\_query\_port(3)

Query non standard attributes of IB device port.

## NAME

mlx5dv\_query\_port - Query non standard attributes of IB device port.

## SYNOPSIS

-

  ```
  #include <infiniband/mlx5dv.h>
  int mlx5dv_query_port(struct ibv_context *context,
                uint32_t port_num,
                struct mlx5dv_port *info);
  ```

## DESCRIPTION

Query port info which can be used for some device commands over the DEVX interface and when directly accessing the hardware resources.

A function that lets a user query hardware and configuration attributes associated with the port.

## USAGE

A user should provide the port number to query. On successful query *flags* will store a subset of the requested attributes which are supported/relevant for that port.

## ARGUMENTS

- *context*

  RDMA device context to work on.

- *port\_num*

  Port number to query.

- \## *info*

  Stores the returned attributes from the kernel.

-

  ```
  struct mlx5dv_port {
      uint64_t flags;
      uint16_t vport;
      uint16_t vport_vhca_id;
      uint16_t esw_owner_vhca_id;
      uint16_t rsvd0;
      uint64_t vport_steering_icm_rx;
      uint64_t vport_steering_icm_tx;
      struct mlx5dv_reg reg_c0;
  };
  ```

- *flags*

  Bit field of attributes, on successful query *flags* stores the valid filled attributes.

  MLX5DV\_QUERY\_PORT\_VPORT: The vport number of that port. MLX5DV\_QUERY\_PORT\_VPORT\_VHCA\_ID: The VHCA ID of *vport\_num*. MLX5DV\_QUERY\_PORT\_ESW\_OWNER\_VHCA\_ID: The E-Switch owner of *vport\_num*. MLX5DV\_QUERY\_PORT\_VPORT\_STEERING\_ICM\_RX: The ICM RX address when directing traffic. MLX5DV\_QUERY\_PORT\_VPORT\_STEERING\_ICM\_TX: The ICM TX address when directing traffic. MLX5DV\_QUERY\_PORT\_VPORT\_REG\_C0: Register C0 value used to identify egress of *vport\_num*.

- *vport*

  The VPORT number of that port.

- *vport\_vhca\_id*

  The VHCA ID of *vport\_num*.

- *rsvd0*

  A reserved field. Not to be used.

- *esw\_owner\_vhca\_id*

  The E-Switch owner of *vport\_num*.

- *vport\_steering\_ica\_rx*

  The ICM RX address when directing traffic.

- *vport\_steering\_icm\_tx*

  The ICM TX address when directing traffic.

- \## reg\_c0

  Register C0 value used to identify traffic of *vport\_num*.

-

  ```
  struct mlx5dv_reg {
          uint32_t value;
          uint32_t mask;
  };
  ```

- *value*

  The value that should be used as match.

- *mask*

  The mask that should be used when matching.

## RETURN VALUE

returns 0 on success, or the value of errno on failure (which indicates the failure reason).

## EXAMPLE

-

  ```
  for (i = 1; i <= ports; i++) {
      ret = mlx5dv_query_port(context, i, &port_info);
      if (ret) {
          printf("Error querying port %d\n", i);
          break;
      }
      printf("Port: %d:\n", i);
      if (port_info.flags & MLX5DV_QUERY_PORT_VPORT)
          printf("\tvport_num: 0x%x\n", port_info.vport_num);
      if (port_info.flags & MLX5DV_QUERY_PORT_VPORT_REG_C0)
          printf("\treg_c0: val: 0x%x mask: 0x%x\n",
                  port_info.reg_c0.value,
                  port_info.reg_c0.mask);
  }
  ```

Mark Bloch ⟨mbloch@nvidia.com⟩\\c