iocblk(D4)

NAME
     iocblk - STREAMS ioctl structure

SYNOPSIS
     #include <sys/stream.h>
     #include <sys/ddi.h>

DESCRIPTION
     The iocblk structure describes a user's ioctl(2) request.

USAGE
     The iocblk structure is used in M_IOCTL, M_IOCACK, and M_IOCNAK messages.
     Modules and drivers usually convert M_IOCTL messages into M_IOCACK or
     M_IOCNAK messages by changing the type and updating the relevant fields
     in the iocblk structure.

     Data cannot be copied to the user's buffer with an M_IOCACK message if
     the ioctl is transparent.

     No data can be copied to the user's buffer with an M_IOCNAK message.

     When processing a transparent ioctl, the iocblk structure is usually
     overlaid with a copyreq(D4) structure.  The stream head guarantees that
     the message is large enough to contain either structure.

   Structure Definitions
     The iocblk structure contains the following members:

     int     ioc_cmd;    /* ioctl command */
     cred_t  *ioc_cr;    /* user credentials */
     uint_t  ioc_id;     /* ioctl ID */
     uint_t  ioc_count;  /* number of bytes of data */
     int     ioc_error;  /* error code for M_IOCACK or M_IOCNAK */
     int     ioc_rval;   /* return value for M_IOCACK */
     The ioc_cmd field is the ioctl command request specified by the user.

     The ioc_cr field contains a pointer to the user credentials.

     The ioc_id field is the ioctl ID, used to uniquely identify the ioctl
     request in the stream.

     The ioc_count field specifies the amount of user data contained in the
     M_IOCTL message.  User data will appear in M_DATA message blocks linked
     to the M_IOCTL message block.  If ioc_count is set to the special value
     TRANSPARENT, then the ioctl request is ``transparent.''  This means that
     the user did not use the I_STR format of STREAMS ioctls and the module or
     driver will have to obtain any user data with M_COPYIN messages, and
     change any user data with M_COPYOUT messages.  In this case, the M_DATA
     message block linked to the M_IOCTL message block contains the value of
     the arg parameter in the ioctl system call.  For an M_IOCACK message, the
     ioc_count field specifies the amount of data to copy back to the user's
     buffer.
     The ioc_error field can be used to set an error for either an M_IOCACK or
     an M_IOCNAK message.

     The ioc_rval field can be used to set the return value in an M_IOCACK
     message.  This will be returned to the user as the return value for the
     ioctl system call that generated the request.

REFERENCES
     copyreq(D4), copyresp(D4), datab(D4), messages(D5), msgb(D4)