net/devlink: Support querying hardware address of port function

PCI PF and VF devlink port can manage the function represented by
a devlink port.

Enable users to query port function's hardware address.

Example of a PCI VF port which supports a port function:
$ devlink port show pci/0000:06:00.0/2
pci/0000:06:00.0/2: type eth netdev enp6s0pf0vf1 flavour pcivf pfnum 0 vfnum 1
  function:
    hw_addr 00:11:22:33:44:66

$ devlink port show pci/0000:06:00.0/2 -jp
{
    "port": {
        "pci/0000:06:00.0/2": {
            "type": "eth",
            "netdev": "enp6s0pf0vf1",
            "flavour": "pcivf",
            "pfnum": 0,
            "vfnum": 1,
            "function": {
                "hw_addr": "00:11:22:33:44:66"
            }
        }
    }
}
Signed-off-by: Parav Pandit <parav@mellanox.com>
Reviewed-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/devlink.h

@@ -1107,6 +1107,18 @@ struct devlink_ops {
 	int (*trap_policer_counter_get)(struct devlink *devlink,
 					const struct devlink_trap_policer *policer,
 					u64 *p_drops);
+	/**
+	 * @port_function_hw_addr_get: Port function's hardware address get function.
+	 *
+	 * Should be used by device drivers to report the hardware address of a function managed
+	 * by the devlink port. Driver should return -EOPNOTSUPP if it doesn't support port
+	 * function handling for a particular port.
+	 *
+	 * Note: @extack can be NULL when port notifier queries the port function.
+	 */
+	int (*port_function_hw_addr_get)(struct devlink *devlink, struct devlink_port *port,
+					 u8 *hw_addr, int *hw_addr_len,
+					 struct netlink_ext_ack *extack);
 };
 
 static inline void *devlink_priv(struct devlink *devlink)

include/uapi/linux/devlink.h

@@ -451,6 +451,8 @@ enum devlink_attr {
 	DEVLINK_ATTR_TRAP_POLICER_RATE,			/* u64 */
 	DEVLINK_ATTR_TRAP_POLICER_BURST,		/* u64 */
 
+	DEVLINK_ATTR_PORT_FUNCTION,			/* nested */
+
 	/* add new attributes above here, update the policy in devlink.c */
 
 	__DEVLINK_ATTR_MAX,
@@ -497,4 +499,12 @@ enum devlink_resource_unit {
 	DEVLINK_RESOURCE_UNIT_ENTRY,
 };
 
+enum devlink_port_function_attr {
+	DEVLINK_PORT_FUNCTION_ATTR_UNSPEC,
+	DEVLINK_PORT_FUNCTION_ATTR_HW_ADDR,	/* binary */
+
+	__DEVLINK_PORT_FUNCTION_ATTR_MAX,
+	DEVLINK_PORT_FUNCTION_ATTR_MAX = __DEVLINK_PORT_FUNCTION_ATTR_MAX - 1
+};
+
 #endif /* _UAPI_LINUX_DEVLINK_H_ */

net/core/devlink.c

@@ -563,6 +563,49 @@ static int devlink_nl_port_attrs_put(struct sk_buff *msg,
 	return 0;
 }
 
+static int
+devlink_nl_port_function_attrs_put(struct sk_buff *msg, struct devlink_port *port,
+				   struct netlink_ext_ack *extack)
+{
+	struct devlink *devlink = port->devlink;
+	const struct devlink_ops *ops;
+	struct nlattr *function_attr;
+	bool empty_nest = true;
+	int err = 0;
+
+	function_attr = nla_nest_start_noflag(msg, DEVLINK_ATTR_PORT_FUNCTION);
+	if (!function_attr)
+		return -EMSGSIZE;
+
+	ops = devlink->ops;
+	if (ops->port_function_hw_addr_get) {
+		int uninitialized_var(hw_addr_len);
+		u8 hw_addr[MAX_ADDR_LEN];
+
+		err = ops->port_function_hw_addr_get(devlink, port, hw_addr, &hw_addr_len, extack);
+		if (err == -EOPNOTSUPP) {
+			/* Port function attributes are optional for a port. If port doesn't
+			 * support function attribute, returning -EOPNOTSUPP is not an error.
+			 */
+			err = 0;
+			goto out;
+		} else if (err) {
+			goto out;
+		}
+		err = nla_put(msg, DEVLINK_PORT_FUNCTION_ATTR_HW_ADDR, hw_addr_len, hw_addr);
+		if (err)
+			goto out;
+		empty_nest = false;
+	}
+
+out:
+	if (err || empty_nest)
+		nla_nest_cancel(msg, function_attr);
+	else
+		nla_nest_end(msg, function_attr);
+	return err;
+}
+
 static int devlink_nl_port_fill(struct sk_buff *msg, struct devlink *devlink,
 				struct devlink_port *devlink_port,
 				enum devlink_command cmd, u32 portid,
@@ -608,6 +651,8 @@ static int devlink_nl_port_fill(struct sk_buff *msg, struct devlink *devlink,
 	spin_unlock_bh(&devlink_port->type_lock);
 	if (devlink_nl_port_attrs_put(msg, devlink_port))
 		goto nla_put_failure;
+	if (devlink_nl_port_function_attrs_put(msg, devlink_port, extack))
+		goto nla_put_failure;
 
 	genlmsg_end(msg, hdr);
 	return 0;