int ibv_query_port(struct ibv_context *context, uint8_t port_num,
                   struct ibv_port_attr *port_attr);

Description

ibv_query_port() returns the attributes of a port of an RDMA device context.

Here is the full description of struct ibv_port_attr:

* supported, but not really relevant

Most of the port attributes, returned by ibv_query_port(), aren't constant and may be changed, mainly by the SM (in InfiniBand), or by the Hardware. It is highly recommended avoiding saving the result of this query, or to flush them when a new SM (re)configures the subnet.

Parameters

Return Values

Examples

Query a port attributes:

struct ibv_port_attr port_attr;
int port_num = 1;
 
rc = ibv_query_port(ctx, port_num, &port_attr);
if (rc) {
	fprintf(stderr, "Error, failed to query port %d attributes in device '%s'\n",
		port_num, ibv_get_device_name(ctx->device));
	return -1;
}

show_port_attr.c

FAQs

I'm using iWarp/IBoE, do I need all of the values that ibv_query_port() returns?

No. Check the protocol columns, to understand which attributes are relevant for you.

I'm using IB, do I need all of the values that ibv_query_port() returns?

No. There are fields that you will use more often (such as state), some you may use when debugging problems (the counters) and some of them are informative for other services.

Calling every time to ibv_query_port() when I need a port attribute takes time, can I cache some of the attributes?

Actually, yes. The attributes, which indicates the port supported attributes (such as supported table length and capabilities) won't change, but others, which are configured by the SM, state and counters may change.

In InfiniBand, if you want, you can cache the returned structure and query it only when an unaffiliated asynchronous event occurred (this will be discussed later on in other posts).

Written by: Dotan Barak on July 21, 2012.on February 17, 2015.