CD_READ_REQ

Section: Communications Device Interface (CDI) (7)
Updated: 2008-10-31
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NAME

CD_READ_REQ - wait for input request

SYNOPSIS

This primitive consists of one M_PROTO(9) or M_PCPROTO(9) message block structured as follows:

typedef struct {
    cd_ulong cd_primitive;
    cd_ulong cd_msec;
} cd_read_req_t;

DESCRIPTION

This user originated primitive requests that an enabled communications device temporarily allow the input section.

When a stream is enabled with CD_ENABLE_REQ(7), it can be used for transmission. If the stream returns CD_AUTOALLOW in the cd_features field of the CD_INFO_ACK(7), the device automatically allows input and there is no need to call the CD_READ_REQ primitive for the device, unless CD_HALT_INPUT_REQ(7) has been successfuly called beforehand.

Parameters

This primitive contains the following parameters:

cd_primitive: Specifies the primitives type.
cd_msec: Specifies the interval of time for which to allow the input section, in units of millisecnds.

State

This primitive is valid in the CD_ENABLED state. When successful, the new state is CD_INPUT_ALLOWED. After the interval cd_msec has expired, the state will revert to CD_ENABLED.

RESPONSE

This primitive requires that the provider acknowledge receipt of the primitive as follows:

Successful: When successful, the provider acknowledges the receipt of this primitivew ith the CD_OK_ACK(7) primitive. The new state is CD_INPUT_ALLOWED.

Unsuccessful (non-fatal errors):

ERRORS

Non-Fatal Errors: applicable non-fatal errors are as follows:"

[CD_BADFRAME]: Defective SDU received.
[CD_BADPRIM]: Unrecognized primitive.
[CD_DISC]: Disconnected.
[CD_EVENT]: Protocol-specific event occurred.
[CD_FATALERR]: Device has become unusable.
[CD_NOTSUPP]: Primitive not supported by this device.
[CD_OUTSTATE]: Primitive was issued from an invalid state.
[CD_PROTOSHORT]: M_PROTO block too short.
[CD_READTIMEOUT]: Read request timed out before data arrived.
[CD_SYSERR]: UNIX system error.

FILES

HISTORY

The Communications Device Interface first appeared in SVR 4[1].

CONFORMANCE

This interface conforms to CDI with Gcom extensions.

REFERENCES

[1]: SVR 4, UNIX® System V Release 4 Programmer's Manual, 1990, (Englewood Cliffs, New Jersey), AT&T UNIX System Laboratories, Inc., Prentice Hall.
[2]: Magic Garden, The Magic Garden Explained: The Internals of UNIX® System V Release 4 / An Open Systems Design, 1994, (Australia), B. Goodheart, J. Cox, Prentice Hall. [ISBN 0-13-098138-9]
[3]: Advanced Programming in the UNIX®Environment, 15th edition, December 1997, (Reading, Massachusetts), W. R. Stevens, Addison Wesley. [ISBN 0-201-56317-7]