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Communications Programming Concepts

DLCSDLC Programming Interfaces

The synchronous data link control (SDLC) device manager (DLCSDLC) conforms to the generic data link control (GDLC) guidelines except where noted in the following list. Additional structures and definitions for DLCSDLC can be found in the /usr/include/sys/sdlextcb.h file.

Note: The GDLC entry-point prefix dlc is replaced with the sdl prefix to denote DLCSDLC device manager operation.
sdlclose DLCSDLC is fully compatible with the dlcclose GDLC interface.
sdlconfig DLCSDLC is fully compatible with the dlcconfig GDLC interface. No initialization parameters are required.
sdlmpx DLCSDLC is fully compatible with the dlcmpx GDLC interface.
sdlopen DLCSDLC is fully compatible with the dlcopen GDLC interface with the following conditions:
  • Single-physical unit (PU) mode allows only one open per port. The open can come from either an application or kernel user, but multiple users cannot share the same port. Single-PU mode is entered by issuing the open without an extension, or by issuing an extended open with the maxsaps (maximum service access points) field set to a value of 0 or 1. Single-PU mode is the default.
  • Multiple-PU mode allows multiple processes to open a secondary port. Multiple-PU mode is entered by issuing an extended open with the maxsaps field set to a value greater than 1.
Note: Only one user process is allowed to open a primary port.
sdlread DLCSDLC is compatible with the dlcread GDLC interface, with the following conditions:
  • Network data is defined as any data received from data communication equipment (DCE) that is not specific to the SDLC session protocol. Examples are X.21 call-progress signals or Smartmodem call-establishment messages. This data must be interpreted differently, depending on the physical attachment in use.
  • Datagram receive data is not supported.
sdlselect DLCSDLC is fully compatible with the dlcselect GDLC interface.
sdlwrite DLCSDLC is compatible with the dlcwrite GDLC interface, with the exception that network data and datagram data are not supported in the send direction. Network data such as X.21 or Smartmodem call-establishment data is sent using the DLC_ENABLE_SAP ioctl operation.
sdlioctl DLCSDLC is compatible with the dlcioctl GDLC interface, with conditions on the following operations:

The following sections describe these conditions.

DLC_ENABLE_SAP

DLCSDLC supports two modes of operation:

The ioctl subroutine argument structure for enabling a service access point (SAP) (dlc_esap_arg) has the following specifics:

DLC_START_LS

DLCSDLC supports up to 254 concurrent link stations (LSs) on a single port when it operates as a multidrop primary node or a multiple-PU secondary node. Only one LS can be started when DLCSDLC operates on a point-to-point connection, or when it is a single-PU secondary node on a multidrop connection.

DLC_ALTER

Specifics for the ioctl subroutine argument structure to alter a link station (dlc_alter_arg) include:

DLC_QUERY_SAP

No device driver-dependent data area is supported by DLCSDLC for the query sap ioctl operation.

DLC_QUERY_LS

No protocol-specific data area is supported by DLCSDLC for the query link station ioctl operation.

DLC_ENTER_SHOLD

DLCSDLC does not currently support the enter_short_hold option.

DLC_EXIT_SHOLD

DLCSDLC does not currently support the exit_short_hold option.

DLC_ADD_GRP

The add_group or multicast address option is not supported by DLCSDLC.

DLC_ADD_FUNC_ADDR

The add_functional_address option is not supported by DLCSDLC.

DLC_DEL_FUNC_ADDR

The delete_functional_address option is not supported by DLCSDLC.

IOCINFO

The ioctype variable is defined as a DD_DLC definition and the subtype returned is DS_DLCSDLC.


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