The nirtfeatures driver is a NILRT-specific, out-of-tree, ACPI driver which provides an API to interact with NI hardware devices equipped with supported CPLD devices.

The nirtfeatures driver is built into all NILRT x64 kernels, but only systems which provide an ACPI device with device id NIC775D will be captured by the driver. When the driver captures a device, it creates a symlink from /dev/nirtfeatures to the sysfs root.



The reset_source sysfs entry is read-only, and exposes a single word which describes the state of the CPLD’s ProcResetSourceReg register. Possible values are defined by the possible return values of the nirtfeatures.c:nirtfeatures_reset_source_get() function.


The CPLD came out of reset due to someone toggling the front-panel reset button.


The CPLD came out of reset because the onboard FPGA received a reset signal.


The CPLD came out of reset because the Ironclad watchdog timer expired.


The system was not reset using the CPLD.


The CPLD came out of reset due to a reset occuring internal to the processor. Most often, this is due to a user-space process rebooting or shutting down the system from software.


The CPLD came out of reset because the processor wrote a 1 to the ResetProcessor bit of the ProcessorModeReg CPLD register.


The CPLD came out of reset because the niwatchdog timer expired.

User Space Tooling

User space tooling for the nirtfeatures driver is provided by the ni-rtfeatures IPK. This IPK includes several initscripts for reporting and handling CPLD register states during system boot.


New in version 9.1.

The /etc/init.d/ni-rtfeatures initscript displays the status of the CPLD reset_source register during boot along with an interpretation of the register’s value. The script reads this value from the /dev/nirtfeatures/reset_source sysfs file if it is present and prints its interpretation to the syslog and stderr in a line like:

Aug 22 19:18:50 ni-rtfeatures: reset_source=processor  # Reset from MAX or command line

Reference the reset_source sysfs documentation for more-detailed documentation of the reset_source values.