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Glossary

anchor

A STREAMS locking mechanism that prevents the removal of STREAMS modules with the I_POP ioctl. Anchors are placed on STREAMS modules by adding the [anchor] flag to autopush configuration files or by directly calling the I_ANCHOR ioctl.

autopush

A STREAMS mechanism that enables a prespecified list of modules to be pushed automatically onto the stream when a STREAMS device is opened. This mechanism is used only for administrative purposes.

back-enable

To enable (by STREAMS) a preceding blocked queue's service procedure when STREAMS determines that a succeeding queue has reached its low-water mark.

blocked

A queue's service procedure that cannot be enabled due to flow control.

clone device

A STREAMS device that returns an unused major/minor device when initially opened, rather than requiring the minor device to be specified by name in the open call.

close routine

A procedure that is called when a module is popped from a stream or when a driver is closed.

controlling stream

A stream above the multiplexing driver used to establish the lower connections. Multiplexed stream configurations are maintained through the controlling stream to a multiplexing driver.

DDI

Device Driver Interface. An interface that facilitates driver portability across different UNIX system versions.

device driver

A stream component whose principle functions are handling an associated physical device and transforming data and information between the external interface and stream.

DKI

Driver-Kernel Interface. An interface between the UNIX system kernel and different types of drivers. It consists of a set of driver-defined functions that are called by the kernel. These functions are entry points into a driver.

downstream

A direction of data flow going from the stream head toward a driver. Also called write side and output side.

driver

A module that forms the stream end. It can be a device driver or a pseudo-device driver. It is a required component in STREAMS (except in STREAMS-based pipe mechanism), and physically identical to a module. It typically handles data transfer between the kernel and a device and does little or no processing of data.

enable

A term used to describe scheduling of a queue's service procedure.

FIFO

First in, first out. A term used in STREAMS for named pipes. This term is also used in queue scheduling.

flow control

A STREAMS mechanism that regulates the rate of message transfer within a stream and from user space into a stream.

hardware emulation module

A module required when the terminal line discipline is on a stream but there is no terminal driver at the end of the stream. This module recognizes all ioctls necessary to support terminal semantics specified by termio and termios.

input side

A direction of data flow going from a driver toward the stream head. Also called read side and upstream.

line discipline

A STREAMS module that performs termio canonical and non-canonical processing. It shares some termio processing with a driver in a STREAMS terminal subsystem.

lower stream

A stream connected below a multiplexer pseudo-device driver, by means of an I_LINK or I_PLINK ioctl. The far end of a lower stream terminates at a device driver or another multiplexer driver.

master driver

A STREAMS-based device supported by the pseudo-terminal subsystem. It is the controlling part of the pseudo-terminal subsystem (also called ptm).

message

One or more linked message blocks. A message is referenced by its first message block and its type is defined by the message type of that block.

message block

A triplet consisting of a data buffer and associated control structures, an msgb structure and a datab structure. It carries data or information, as identified by its message type, in a stream.

message queue

A linked list of zero or more messages connected together.

message type

A defined set of values identifying the contents of a message.

 
 
 
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