M_IOCDATA

Generated by the Stream head and sent downstream as a response to an M_COPYIN or M_COPYOUT message. The message format is one M_IOCDATA message block followed by zero or more M_DATA blocks. The M_IOCDATA message block contains a copyresp(9S), defined in <sys/stream.h>.

struct copyresp {
	int			cp_cmd;							/* ioctl cmd (fr ioc_cmd) */
	cred_t *cp_cr;										/* full credentials */
	uint			cp_id;							/* ioctl id (from ioc_id) */
	caddr_t			 cp_rval;							/* status of request */
	mblk_t			*cp_private;							/* state info */
};

The first three members of the structure correspond to those of the iocblk(9S) in the M_IOCTL message that allows the same message blocks to be reused for all of the related transparent messages (M_COPYIN, M_COPYOUT, M_IOCACK, M_IOCNAK). The cp_rval field contains the result of the request at the Stream head. Zero indicates success and non-zero indicates failure. If failure is indicated, the module should not generate an M_IOCNAK message. It must abort all ioctl(2) processing, clean up its data structures, and return.

The cp_private field is copied from the cq_private field in the associated M_COPYIN or M_COPYOUT message. It is included in the M_IOCDATA message so the message can be self-describing. This is intended to simplify ioctl(2) processing by modules and drivers.

If the message is in response to an M_COPYIN message and success is indicated, the M_IOCDATA block will be followed by M_DATA blocks containing the data copied in.

If an M_IOCDATA block is reused, any unused fields defined for the resultant message block should be cleared (particularly in an M_IOCACK or M_IOCNAK).

This message should not be queued by a module or driver unless it processes the data for the ioctl in some way.