module_info(D4DK) —

NAME

module_info − STREAMS driver and module information structure

SYNOPSIS

#include <sys/types.h>
#include <sys/conf.h>
#include <sys/stream.h>

DESCRIPTION

When a module or driver is declared, several identification and limit values can be set. These values are stored in the module_info structure. These values are used to initialize the module’s or driver’s queues when they are created.

After the initial declaration, the module_info structure is intended to be read-only. However, the flow control limits (mi_hiwat and mi_lowat) and the packet size limits (mi_minpsz and mi_maxpsz) are copied to the queue(D4DK) structure, where they may be modified.

STRUCTURE MEMBERS

ushort_t	mi_idnum;	/∗ module ID number ∗/
char	∗mi_idname;	/∗ module name ∗/
long	mi_minpsz;	/∗ minimum packet size ∗/
long	mi_maxpsz;	/∗ maximum packet size ∗/
ulong_t	mi_hiwat;	/∗ high water mark ∗/
ulong_t	mi_lowat;	/∗ low water mark ∗/

The mi_idnum field is a unique identifier for the driver or module that distinguishes the driver or module from the other drivers and modules in the system.

The mi_idname field points to the driver or module name. The constant FMNAMESZ limits the length of the name, not including the terminating NULL. It is currently set to eight characters.

The mi_minpsz field is the default minimum packet size for the driver or module queues. This is an advisory limit specifying the smallest message that can be accepted by the driver or module.

The mi_maxpsz field is the default maximum packet size for the driver or module queues. This is an advisory limit specifying the largest message that can be accepted by the driver or module.

The mi_hiwat field is the default high water mark for the driver or module queues. This specifies the number of bytes of data contained in messages on the queue such that the queue is considered full and hence flow-controlled.

The mi_lowat field is the default low water mark for the driver or module queues. This specifies the number of bytes of data contained in messages on the queue such that the queue is no longer flow-controlled.

NOTES

There may be one module_info structure per read and write queue, or the driver or module may use the same module_info structure for both the read and write queues.

A stream may refuse to accept or process messages smaller than the largest mi_minpsz or larger than the smallest mi_maxpsz on that stream.