streamio.7 (2010 09)

s
streamio(7) streamio(7)
RMSGN Message-nondiscard mode.
Setting both
RMSGD and RMSGN is an error.
RMSGD and RMSGN override NORM.
In addition, treatment of control messages by the stream head may be changed by
setting the following flags in arg:
RPROTNORM Fail read with EBADMSG if a control message is at the front
of the stream head read queue. This is the default behavior.
RPROTDAT Deliver the control portion of a message as data when a user
issues read.
RPROTDIS Discard the control portion of a message, delivering any data
portion, when a user issues a read.
I_STR Constructs an internal STREAMS ioctl message from the data pointed to by arg,
and sends that message downstream.
This mechanism is provided to send user
ioctl requests to downstream modules
and drivers. It allows information to be sent with the
ioctl, and will return to the
user any information sent upstream by the downstream recipient.
I_STR blocks
until the system responds with either a positive or negative acknowledgement mes-
sage, or until the request "times out" after some period of time. If the request times
out, it fails with
errno set to ETIME.
At most, one
I_STR can be active on a stream. Further
I_STR calls will block
until the active
I_STR completes at the stream head. The default timeout intervals
for these requests is 15 seconds. The O_NONBLOCK (see open(2)) flags have no
effect on this call.
To send requests downstream, arg must point to a
strioctl structure which con-
tains the following members:
int ic_cmd;
int ic_timout;
int ic_len;
char *ic_dp;
ic_cmd is the internal ioctl command intended for the downstream module or
driver and ic_timout is the number of seconds (−1 =infinite, 0 = use default, >0 =
as specified) an I_STR request will wait for acknowledgement before timing out.
The default timeout is infinite. ic_len is the number of bytes in the data argu-
ment and ic_dp is a pointer to the data argument. The ic_len field has two
uses: on input, it contains the length of the data argument passed in, and on return
from the command, it contains the number of bytes being returned to the user (the
buffer pointed to by ic_dp should be large enough to contain the maximum amount
of data that any module or driver in the stream can return). The stream head will
convert the information pointed to by strioctl structure to an internal ioctl
command message and send it downstream.
I_SWROPT Sets the write mode using the value of the argument arg. Legal bit settings for arg
are:
SNDZERO Sends a zero-length message downstream when a write of 0
bytes occurs. To not send a zero-length message when a write
of 0 bytes occurs, this bit must not be set in arg .
I_UNLINK Disconnects the two streams specified by fildes and arg. fildes is the file descriptor
of the stream connected to the multiplexing driver. arg is the multiplexor ID
number that was returned by the I_LINK.Ifarg is MUXID_ALL, then all streams
which were linked to fildes are disconnected. As in I_LINK, this command
requires the multiplexing driver to acknowledge the unlink.
RETURN VALUE
Unless specified differently for a command, the return value for a STREAMS
ioctl() call is 0 (zero) on
success and −1 (minus one) on failure.
6 Hewlett-Packard Company − 6 − HP-UX 11i Version 3: September 2010