Introduction

Supported Linux Kernels

• 2.4-based kernels on Intel and Alpha platforms
• 2.2-based kernels on Intel and Alpha platforms
• 2.0-based kernels equal or newer than 2.0.36 on Intel platforms

The driver package has been tested with the following unmodified Linux distributions:

• RedHat 6.2
• RedHat 7.0
• RedHat 7.1
• RedHat 7.2
• SuSe 7.1
• SuSe 7.0
• SuSe 6.4
• Conectiva 6.0
• TurboLinux 6.1 workstation
• TurboLinux 6.0 server
• Mandrake 7.2

Supported Products

• Digi One RealPort Device Server
• EtherLite 2
• EtherLite 8
• EtherLite 16
• EtherLite 32
• EtherLite 80
• EtherLite 160
• EtherLite 162
• PortServer 8
• PortServer 16
• PortServer II 16
• PortServer TS 2
• PortServer TS 4
• PortServer TS 8
• PortServer TS 16

Enhancements

Bug Fixes

• Modified driver to prevent port "hangup" in the event that the daemon dies.
• Added TCFLSH handling to "ditty-rp"... previously, the "flushin", "flushout", and "flush" options didn't work.

Known Limitations

Printers

Ditty

Configuration and Startup

The software package includes two startup scripts in either the /etc/rc.d/init.d or /etc/init.d directories named "dgrp_daemon" and "dgrp_ditty". These scripts will be executed at startup automatically if the "chkconfig" tool is present on the system during the post installation phase of the driver install. Otherwise, these scripts must be manually added to the system startup.

RedHat 7.1 -- Kernel Compatibility Issues

Some 2.4 kernel-based distributions (RedHat 7.1 included) have a patch applied to them which modifies the behavior of Linux when an open of a serial port is canceled (for instance, if an application is waiting for the carrier signal and a user hits CTRL-C to kill the application).

With this behavior change, the device driver is unable to cleanup its internal data structures and the sane functioning of the driver is compromised. The classic symptom of this problem is that the command "lsmod", which (among other things) will return a count of the applications using the device driver, will return a non-zero value even if all applications associated with the serial ports are killed.

Unfortunately, it is impossible (from within the device driver) to determine which behavior is implemented in the running kernel. However, Digi now provides a workaround to allow customers with this problem to change the Digi behavior to be compatible with these "patched" kernels.

To enable the change which provides alternate behavior when a serial "open" call fails, execute the following after the device driver is loaded:

echo "alt_fail_open=1" > /proc/dgrp/info

To return to the standard behavior, execute:

echo "alt_fail_open=0" > /proc/dgrp/info

To examine the current state of this driver tuning variable:

cat /proc/dgrp/info

Unfortunately, this command must be executed each time the device driver is loaded (i.e. when the system is booted). To make this process easier for customers, the Digi standard driver startup tools will execute the command on the customer's behalf when it loads the driver if the following command is executed:

touch /usr/bin/dgrp/config/alt_fail_open

• Version 1.3-0:
  • Added full support for Digi's EtherLite products which are running Digi RealPort compatible firmware, including the EtherLite 2, EtherLite 160, EtherLite 162, and the EtherLite 80. Fixed a kernel panic if a port is open, `dgrp_daemon stop` is executed, and a program then goes to write to the still open port. Now write returns EIO in that condition. Fixed a select(2) problem in kernel 2.2.15 and later of 2.2.x kernels which could cause programs like telnet or ssh to appear to hang until a key is pressed. Fixed a data loss problem which would manifest itself when exactly four kilobytes of data were transmitted after a port was opened. Added /lib/modules/`uname -r`/kernel/drivers/char to the list of locations that the kit will test for existence when trying to find an appropriate location to install the driver module, in response to testing in native 2.4 kernel-based distributions.
  • Version 1.2-2: Increased support for Digi's ethernet-based serial connectivity family; including Digi One, EtherLite, and PortServer products. Added support for arbitrary integer baud rates via the "ditty-rp" utility. Detailed information about the type and version of configured remote devices was made available via the "/proc/dgrp/nodeinfo" file. A memory corruption problem which would cause sysem instability was eliminated. Unexpected pauses and loss in port traffic as a result of a network buffer overflow were resolved.
  • Version 1.1-7: Added 2.4 kernel support. Removed references to invalid email addresses. Driver now handles RedHat 7.0 (kgcc vs. gcc). The GUI tool now displays the DCD signal when viewing ports. RealPort ports now match other Linux serial ports for default settings, as well as making all port settings "sticky". As a result of this change, CLOCAL is now on by default. Configuration scripts remove the "/dev" files if a PortServer is unconfigured. Only physical line drops are detected as a "hangup" condition... the driver would previously treat a change from CLOCAL to -CLOCAL as a carrier transition. Startup scripts are installed in "/etc/init.d" if "/etc/rc.d/init.d" does not exist. RPM installation will not "error out" if "chkconfig" (a RedHat tool) does not exist on the system. A message was added to the RPM installation to communicate to users whether the installation scripts were added or not. On newer systems, RPM would inadvertently strip the driver module of its symbols, causing it to fail. The module is no longer stripped.
  • Version 1.0-0: Added a new proc file: /proc/dgrp/info. This file allows one to determine the value of a number of state variables associated with the driver, including the driver revision. Continued refinement of the GUI. The GUI is now distributed as a single file, rather than a collection of "tcl" files. dgrp_cfg_node now does validity checking of its ID and COUNT parameters.
  • Version 0.1-7: A first pass at cleaning up the code was completed for beta release. All driver build warnings have been fixed. Appropriate part numbers have been correctly placed in the appropriate documents. A useful driver revision number is now placed in the console log when the module is loaded.
  • Version 0.1-5: a minimum break time of 250ms is now enforced. A PPP hang problem was resolved. Continued enhancements of the packaging.
  • Version 0.1-4: decided to install dgrp.o to the /usr/bin/dgrp directory, and then link in the postinstall phase to a suitable /lib/modules/*/misc directory. This avoids the problem of having the path to dgrp.o hardcoded in the spec file.
  • Version 0.1-3: added new scripts to autoload the driver on system startup and initialize any PortServers configured in /etc/dgrp.backing.store
  • Version 0.1-1 - pilot release in January 1999