write(2)/read(2) commands
-------------------------
There is only one buffer/struct defined for writing/reading to the sol_umad
driver:

struct ib_user_mad {
	struct ib_user_mad_hdr	hdr;	 /* Header struct */
	u64			data[0]; /* MAD payload data */
};

where 'struct ib_user_mad_hdr' is:

struct ib_user_mad_hdr {
	uint32_t   id;		/* ID of agent MAD received with/to be sent */
				/* with */
	uint32_t   status;	/* 0 on successful receive, ETIMEDOUT if no */
				/* response received (transaction ID in */
				/* data[] will be set to TID of original */
				/* request) (ignored on send) */
	uint32_t   timeout_ms;	/* Milliseconds to wait for response (unset */
				/* on receive) */
	uint32_t   retries;	/* Number of automatic retries to attempt */
	uint32_t   length;	/* */
	uint32_t   qpn;		/* Remote QP number received from/to be sent */
				/* to */
	uint32_t   qkey;	/* Remote Q_Key to be sent with (unset on */
				/* receive) */
	uint16_t   lid;		/* Remote lid received from/to be sent to */
	uint8_t    sl;		/* Service level received with/to be sent */
				/* with */
	uint8_t    path_bits;	/* Local path bits received with/to be sent */
				/* with */
	uint8_t    grh_present;	/* If set, GRH was received/should be sent */
	uint8_t    gid_index;	/* Local GID index to send with (unset on */
				/* receive) */
	uint8_t    hop_limit;	/* Hop limit in GRH  */
	uint8_t    traffic_class;	/* Traffic class in GRH  */
	uint8_t    gid[16];	/* Remote GID in GRH */
	uint32_t  flow_label;	/* Flow label in GRH */
	uint16_t   pkey_index;	/* P_Key index */
	uint8_t    reserved[6];
};

ioctl(2) commands
-----------------
There are three ioctl requests supported:

	IB_USER_MAD_REGISTER_AGENT	/* MAD registration request */
	IB_USER_MAD_UNREGISTER_AGENT	/* MAD unregistration request */
	IB_USER_MAD_ENABLE_PKEY		/* Enable extended interface request */
	

Details of which are:

ioctl request:	IB_USER_MAD_REGISTER_AGENT

ioctl arg: 	pointer to an struct ib_user_mad_reg_req defined as:

struct ib_user_mad_reg_req {
	uint32_t   	id;	/* Set by the kernel; used to identify agent */
				/* in future requests */

	packed_ulong	method_mask[IB_USER_MAD_LONGS_PER_METHOD_MASK];

				/* The caller will receive unsolicited MADs */
				/* for any method where @method_mask = 1 */

	uint8_t    qpn;		/* Queue pair number; must be 0 or 1 */

	uint8_t    mgmt_class;	/* Indicates which management class of MADs */
				/* should be receive by the caller. This */
				/* field is only required if the user wishes */
				/* to receive unsolicited MADs, otherwise it */
				/* should be 0. */

	uint8_t    mgmt_class_version;

				/* Indicates which version of MADs for the */
				/* given  management class to receive */

	uint8_t    oui[3];	/* Indicates IEEE OUI when mgmt_class is a */
				/* vendor class in the range from 0x30 to */
				/* 0x4f. Otherwise not used. */

	uint8_t    rmpp_version;	/* If set, indicates the RMPP version */
					/* used */
};




ioctl request:	IB_USER_MAD_UNREGISTER_AGENT

ioctl arg: 	pointer to an uint32_t that is the 'id' obtained from a
		previous IB_USER_MAD_REGISTER_AGENT   operation.





ioctl request:	IB_USER_MAD_ENABLE_PKEY

ioctl arg: 	NULL	

This ioctl enables the newer read(2)/write(2) interface defined by
struct ib_user_mad above. This interface allows specifying/receiving the
P_Key index.  To use this interface, an application must call the
IB_USER_MAD_ENABLE_PKEY ioctl on the user MAD file handle before any other
actions with the file handle.