CD_UNITDATA_REQ

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

CD_UNITDATA_REQ - data send request

SYNOPSIS

This primitive consists of one M_PROTO(9) message block followed by one or more M_DATA(9) message blocks. The M_PROTO(9) message block is structured as follows:

typedef struct {
    cd_ulong cd_primitive;
    cd_ushort cd_addr_type;
    cd_ushort cd_priority;
    cd_ulong cd_dest_addr_length;
    cd_ulong cd_dest_addr_offset;
} cd_unitdata_req_t;

DESCRIPTION

This user originated primitive requests that the specified data be sent to the specified destination address with the specified priority.

Parameters

This primitive contains the following parameters:

cd_primitive

Specifies the primitives type.

cd_addr_type

CD_SPECIFIC: Specifies that an address is contained in the primitive. When cd_addr_type is set to CD_SPECIFIC, a destination address must be specified in the cd_dest_addr_length and cd_dest_addr_offset fields.
CD_BROADCAST: Specifies that the data is to be sent to the implicit broadcast address and no specific address follows. When cd_addr_type is set to CD_BROADCAST, the fields cd_dest_addr_length and cd_dest_addr_offset should be coded zero (0) and are ignored by the CD provider.
CD_IMPLICIT: Specifies that an implicit address is to be used, or that the address is embedded in the data. When cd_addr_type is set to CD_IMPLICIT, the fields cd_dest_addr_length and cd_dest_addr_offset should be coded zero (0) and are ignored by the CD provider. No address or embedded address.

cd_priority

Specifies the priority of the data. Priorities are provider- and device-specific.

cd_dest_addr_length

When cd_addr_type is CD_SPECIFIC, this field specifies the length of the destination address to which to send the message. Otherwise, this field is coded zero (0) and ignored by the CD provider.

cd_dest_addr_offset

When cd_addr_type is CD_SPECIFIC, this field specifies the offset of the destination address from the start of the M_PROTO(9) message block. Otherwise, this field is ignored by the CD provider.

State

This primitive is valid in states CD_ENABLED, CD_INPUT_ALLOWED, CD_OUTPUT_ACTIVE, CD_READ_ACTIVE. The state remains unchanged.

RESPONSE

This primitive requires an acknowledgement under the following conditions:

Successful: When field cd_output_style in CD_INFO_ACK(7) is set to CD_ACKEDOUTPUT, then the provider is required to acknowledge the CD_UNITDATA_REQ with a CD_UNITDATA_ACK(7). Otherwise, the primitive does not require an acknowledgement. In either case, the state remains unchanged.

Unsuccessful (non-fatal errors): When unsuccessful, the provider is required to acknowledge the primitive with a CD_ERROR_ACK(7) primitive indicating the error.

ERRORS

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

[CD_BADADDRESS]: Address was invalid.
[CD_BADADDRTYPE]: Invalid address type.
[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_SYSERR]: UNIX system error.
[CD_WRITEFAIL]: Unitdata request failed.

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]