Copyright (c) 1997, Sun Microsystems, Inc.
The contents of this file are subject to the terms of the Common Development and Distribution License (the "License"). You may not use this file except in compliance with the License.
You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE or http://www.opensolaris.org/os/licensing. See the License for the specific language governing permissions and limitations under the License.
When distributing Covered Code, include this CDDL HEADER in each file and include the License file at usr/src/OPENSOLARIS.LICENSE. If applicable, add the following below this CDDL HEADER, with the fields enclosed by brackets "[]" replaced with your own identifying information: Portions Copyright [yyyy] [name of copyright owner]
#include <fcntl.h>
open(/dev/zshn, mode );
open(/dev/zsh, mode );
The zsh module is a loadable STREAMS driver that implements the sending and receiving of data packets as HDLC frames over synchronous serial lines. The module is not a standalone driver, but instead depends upon the zs module for the hardware support required by all on-board serial devices. When loaded this module acts as an extension to the zs driver, providing access to an HDLC interface through character-special devices.
The zshn devices provide what is known as a data path which supports the transfer of data via read(2) and write(2) system calls, as well as ioctl(2) calls. Data path opens are exclusive in order to protect against injection or diversion of data by another process.
The zsh device provides a separate control path for use by programs that need to configure or monitor a connection independent of any exclusive access restrictions imposed by data path opens. Up to three control paths may be active on a particular serial channel at any one time. Control path accesses are restricted to ioctl(2) calls only; no data transfer is possible.
When used in synchronous modes, the Z8530 SCC supports several options for clock sourcing and data encoding. Both the transmit and receive clock sources can be set to be the external Transmit Clock (TRxC), external Receive Clock (RTxC), the internal Baud Rate Generator (BRG), or the output of the SCC's Digital Phase-Lock Loop (DPLL).
The Baud Rate Generator is a programmable divisor that derives a clock frequency from the PCLK input signal to the SCC. A programmed baud rate is translated into a 16-bit time constant that is stored in the SCC. When using the BRG as a clock source the driver may answer a query of its current speed with a value different from the one specified. This is because baud rates translate into time constants in discrete steps, and reverse translation shows the change. If an exact baud rate is required that cannot be obtained with the BRG, an external clock source must be selected.
Use of the DPLL option requires the selection of NRZI data encoding and the setting of a non-zero value for the baud rate, because the DPLL uses the BRG as its reference clock source.
A local loopback mode is available, primarily for use by the syncloop(1M) utility for testing purposes, and should not be confused with SDLC loop mode, which is not supported on this interface. Also, an auto-echo feature may be selected that causes all incoming data to be routed to the transmit data line, allowing the port to act as the remote end of a digital loop. Neither of these options should be selected casually, or left in use when not needed.
The zsh driver keeps running totals of various hardware generated events for each channel. These include numbers of packets and characters sent and received, abort conditions detected by the receiver, receive CRC errors, transmit underruns, receive overruns, input errors and output errors, and message block allocation failures. Input errors are logged whenever an incoming message must be discarded, such as when an abort or CRC error is detected, a receive overrun occurs, or when no message block is available to store incoming data. Output errors are logged when the data must be discarded due to underruns, CTS drops during transmission, CTS timeouts, or excessive watchdog timeouts caused by a cable break.
The zsh driver supports several ioctl() commands, including: S_IOCGETMODE
Return a struct scc_mode containing parameters currently in use. These include the transmit and receive clock sources, boolean loopback and NRZI mode flags and the integer baud rate.
The argument is a struct scc_mode from which the SCC channel will be programmed.
Return a struct sl_stats containing the current totals of hardware-generated events. These include numbers of packets and characters sent and received by the driver, aborts and CRC errors detected, transmit underruns, and receive overruns.
Clear the hardware statistics for this channel.
Returns the currently set baud rate as an integer. This may not reflect the actual data transfer rate if external clocks are used.
Returns the current state of the CTS and DCD incoming modem interface signals as an integer.
The following structures are used with zsh ioctl() commands:
struct scc_mode {
char sm_txclock; /* transmit clock sources */
char sm_rxclock; /* receive clock sources */
char sm_iflags; /* data and clock inversion flags (non-zsh) */
uchar_t sm_config; /* boolean configuration options */
int sm_baudrate; /* real baud rate */
int sm_retval; /* reason codes for ioctl failures */
};
struct sl_stats {
long ipack; /* input packets */
long opack; /* output packets */
long ichar; /* input bytes */
long ochar; /* output bytes */
long abort; /* abort received */
long crc; /* CRC error */
long cts; /* CTS timeouts */
long dcd; /* Carrier drops */
long overrun; /* receive overrun */
long underrun; /* transmit underrun */
long ierror; /* input error */
long oerror; /* output error */
long nobuffers; /* receive side memory allocation failure */
};
An open() will fail if a STREAMS message block cannot be allocated, or: ENXIO
The unit being opened does not exist.
The device is in use by another serial protocol.
An ioctl() will fail if: EINVAL
An attempt was made to select an invalid clocking source.
The baud rate specified for use with the baud rate generator would translate to a null time constant in the SCC's registers.
character-special devices
header file specifying synchronous serial communication definitions
See attributes(5) for descriptions of the following attributes:
| ATTRIBUTE TYPE ATTRIBUTE VALUE |
| Architecture x86 |
syncinit(1M), syncloop(1M), syncstat(1M), ioctl(2), open(2), read(2), write(2), attributes(5), zs(7D)
Refer to the Zilog Z8530 SCC Serial Communications Controller Technical Manual for details of the SCC's operation and capabilities.
A kernel memory allocation failed for one of the private data structures. The value of nnn is the address of the read queue passed to open(2).
The open could not proceed because an initial STREAMS message block could not be made available for incoming data.
An operation was attempted through a control path before that path had been attached to a particular serial channel.
An inappropriate STREAMS message type was passed through a control path. Only M_IOCTL and M_PROTO message types are permitted.
An M_DATA message was passed to the driver for a channel that had not been programmed at least once since the driver was loaded. The SCC's registers were in an unknown state. The S_IOCSETMODE ioctl command performs the programming operation.
The transmitter was not successfully restarted after the watchdog timer expired.