miocack(9F) Kernel Functions for Drivers miocack(9F)NAME
miocack - Positively acknowledge an M_IOCTL message
SYNOPSIS
#include <sys/stream.h>
#include <sys/strsun.h>
void miocack(queue_t *wq, mblk_t *mp, intcount, int rval);
INTERFACE LEVEL
Solaris DDI specific (Solaris DDI).
PARAMETERS
wq Write queue associated with the read queue to send the M_IOCACK on.
mp M_IOCTL message.
count Value to set the ioc_count of the iocblk(9S) to.
rval Value to set the ioc_rval of the iocblk(9S) to.
DESCRIPTION
The miocack() function converts an M_IOCTL message into a M_IOCACK message and sends the resulting message upstream.
To convert the message, miocack() changes the message type to M_IOCACK, sets the 'ioc_count' and 'ioc_rval' members of the iocblk(9S) asso-
ciated with mp to the passed-in values, and clears the 'ioc_error' field. If the caller specifies a non-zero value for count, it is
expected that the caller has already set 'mp->b_cont' field to point to a message block with a length of at least count bytes.
Callers that only need to perform the message conversion, or need to perform additional steps between the conversion and the sending
of the M_IOCACK should use mioc2ack(9F).
RETURN VALUES
None.
CONTEXT
This function can be called from user, kernel or interrupt context.
NOTES
Callers must not hold any locks across a miocack() that can be acquired as part of put(9E) processing.
SEE ALSO mioc2ack(9F), put(9E), iocblk(9S)
STREAMS Programming Guide
SunOS 5.11 9 June 2004 miocack(9F)
Check Out this Related Man Page
mkiocb(9F) Kernel Functions for Drivers mkiocb(9F)NAME
mkiocb - allocates a STREAMS ioctl block for M_IOCTL messages in the kernel.
SYNOPSIS
#include <sys/stream.h>
mblk_t *mkiocb(uint_t command);
INTERFACE LEVEL
Solaris DDI specific (Solaris DDI).
PARAMETERS
command ioctl command for the ioc_cmd field.
DESCRIPTION
STREAMS modules or drivers might need to issue an ioctl to a lower module or driver. The mkiocb() function tries to allocate (using
allocb(9F)) a STREAMS M_IOCTL message block (iocblk(9S)). Buffer allocation fails only when the system is out of memory. If no buffer is
available, the qbufcall(9F) function can help a module recover from an allocation failure.
The mkiocb function returns a mblk_t structure which is large enough to hold any of the ioctl messages (iocblk(9S), copyreq(9S) or copy-
resp(9S)), and has the following special properties:
b_wptr Set to b_rptr + sizeof(struct iocblk).
b_cont Set to NULL..
b_datap->db_type Set to M_IOCTL.
The fields in the iocblk structure are initialized as follows:
ioc_cmd Set to the command value passed in.
ioc_id Set to a unique identifier.
ioc_cr Set to point to a credential structure encoding the maximum system privilege and which does not need to be freed in any fash-
ion.
ioc_count Set to 0.
ioc_rval Set to 0.
ioc_error Set to 0.
ioc_flags Set to IOC_NATIVE to reflect that this is native to the running kernel.
RETURN VALUES
Upon success, the mkiocb() function returns a pointer to the allocated mblk_t of type M_IOCTL.
On failure, it returns a null pointer.
CONTEXT
The mkiocb() function can be called from user, interrupt, or kernel context.
EXAMPLES
Example 1 M_IOCTL Allocation
The first example shows an M_IOCTL allocation with the ioctl command TEST_CMD. If the iocblk(9S) cannot be allocated, NULL is returned,
indicating an allocation failure (line 5). In line 11, the putnext(9F) function is used to send the message downstream.
1 test_function(queue_t *q, test_info_t *testinfo)
2 {
3 mblk_t *mp;
4
5 if ((mp = mkiocb(TEST_CMD)) == NULL)
6 return(0);
7
8 /* save off ioctl ID value */
9 testinfo->xx_iocid = ((struct iocblk *)mp->b_rptr)->ioc_id;
10
11 putnext(q, mp); /* send message downstream */
12 return(1);
13 }
Example 2 The ioctl ID Value
During the read service routine, the ioctl ID value for M_IOCACK or M_IOCNAK should equal the ioctl that was previously sent by this module
before processing.
1 test_lrsrv(queue_t *q)
2 {
3 ...
4
5 switch (DB_TYPE(mp)) {
6 case M_IOCACK:
7 case M_IOCNAK:
8 /* Does this match the ioctl that this module sent */
9 ioc = (struct iocblk*)mp->b_rptr;
10 if (ioc->ioc_id == testinfo->xx_iocid) {
11 /* matches, so process the message */
12 ...
13 freemsg(mp);
14 }
15 break;
16 }
17 ...
18 }
Example 3 An iocblk Allocation Which Fails
The next example shows an iocblk allocation which fails. Since the open routine is in user context, the caller may block using qbufcall(9F)
until memory is available.
1 test_open(queue_t *q, dev_t devp, int oflag, int sflag,
cred_t *credp)
2 {
3 while ((mp = mkiocb(TEST_IOCTL)) == NULL) {
4 int id;
5
6 id = qbufcall(q, sizeof (union ioctypes), BPRI_HI,
7 dummy_callback, 0);
8 /* Handle interrupts */
9 if (!qwait_sig(q)) {
10 qunbufcall(q, id);
11 return (EINTR);
12 }
13 }
14 putnext(q, mp);
15 }
SEE ALSO allocb(9F), putnext(9F), qbufcall(9F), qwait_sig(9F), copyreq(9S), copyresp(9S), iocblk(9S)
Writing Device Drivers
STREAMS Programming Guide
WARNINGS
It is the module's responsibility to remember the ID value of the M_IOCTL that was allocated. This will ensure proper cleanup and ID match-
ing when the M_IOCACK or M_IOCNAK is received.
SunOS 5.11 16 Jan 2006 mkiocb(9F)