NAME

queue - STREAMS queue structure

SYNOPSIS

#include <sys/stream.h>

INTERFACE LEVEL

Architecture independent level 1 (DDI/DKI).

DESCRIPTION

A STREAMS driver or module consists of two queue structures, one for upstream processing (read) and one for downstream processing (write). This structure is the major building block of a stream. It contains pointers to the processing procedures, pointers to the next and previous queues in the stream, flow control parameters, and a pointer defining the position of its messages on the STREAMS scheduler list.

The queue structure is defined as type queue_t.

STRUCTURE MEMBERS

struct qinit

* q_qinfo;

/* module or driver entry points * /

struct msgb   * q_first;    /* first message in queue * /
struct msgb   * q_last;    /* last message in queue * /
struct queue  * q_next;    /* next queue in stream * /
struct queue  * q_link;    /* tonext queue for scheduling* /
void          * q_ptr;     /* pointer to private data structure * /
ulong         q_count;     /* approximate size of message queue * /
ulong         q_flag;       /* status of queue * /
long          q_minpsz;    /* smallest packet accepted by QUEUE * /
long          q_maxpsz;    /* largest packet accepted by QUEUE * /
ulong         q_hiwat;     /* high water mark * /
ulong         q_lowat;     /* low water mark * /

Valid flags are as follows:

QENAB

queue is already enabled to run.

QWANTR

someone wants to read queue.

QWANTW

someone wants to write to queue.

QFULL

queue is considered full.

QREADR

this is the reader (first) queue.

QUSE

this queue in use (allocation).

QNOENB

do not enable queue via putq.

SEE ALSO

strqget(9F), strqset(9F), msgb (9S),module_info(9S), streamtab(9S), qinit(9S)

Writing Device Drivers

STREAMS Programmer's Guide