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SWSENSOR(4) Kernel Interfaces Manual SWSENSOR(4)


swsensorsoftware environmental sensor


pseudo-device swsensor


The swsensor driver provides a software environmental sensor that works with sysctl(8) and envstat(8). The driver is intended to be loaded as a kernel module. One can, however, include the swsensor driver directly in a kernel using the configuration from the synopsis. By default, the sensor is of type ENVSYS_UNITS_INTEGER.

The following values can be specified in the modload(8) command when loading the swsensor module to alter the driver's behavior.

Variable Usage
Controls whether or not swsensor provides internally-maintained limits and limit checking
Value Meaning
sensor has no internally-maintained limits
sensor provides its own internal limit value
sensor maintains an internal adjustable limit and performs its own comparison between the sensor's limit and its current value
The initial alarm limit value, if limit emulation is selected (i.e., if mode is set to 1 or 2)
The maximum and minimum values. The corresponding ENVSYS_FVALID_MAX and ENVSYS_FVALID_MIN flags are implicitly set.
This boolean value controls the setting of the ENVSYS_FPERCENT flag.
Define the sensor's unit/type. By default, a Temperature sensor is created. Any of the string values from the following table can be specified:
Temperature Fan Voltage AC
Voltage DC Ohms Watts
Ampere Watt hour Ampere hour
Indicator Integer Drive
Battery capacity Battery charge
(Values are case-sensitive, and spaces must be included.)
Provide an initial value for the sensor. If this is omitted, the sensor's initial value is set to zero.

For example,

modload -s type=Voltage\ DC swsensor
will create a sensor of type ENVSYS_UNITS_SVOLTS_DC, while
modload -i mode=1 -i limit=50 swsensor
will create a sensor which has an initial, device-provided limit of 50.

The sensor's raw value and state can be manually updated by modifying the sysctl(8) variables “hw.swsensor.cur_value” and “hw.swsensor.state” variables respectively.


The swsensor driver was written by Paul Goyette and first appeared in NetBSD 6.0.


The swsensor driver emulates a device with only a single sensor.

The swsensor driver can only emulate one hardware-managed limit; this is assumed to be the critical-min limit.

August 27, 2012 NetBSD 7.0