iocblk(D4)iocblk(D4)NAMEiocblk - 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.
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iocblk(D4)iocblk(D4)
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.
REFERENCEScopyreq(D4), copyresp(D4), datab(D4), messages(D5), msgb(D4)
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