lmenv —
National Semiconductor LM81, LM87, and compatible hardware
  monitors
lmenv0 at iic0 addr 0x2c: ADM9240 rev 2
The lmenv driver provides support for the National
  Semiconductor LM87, National Semiconductor LM81, Analog Devices ADM9240, and
  Dallas Semiconductor DS1780 iicbus hardware monitors. Sensor values are
  reported through the envstat(8)
  interface.
The lmenv supports the following voltage,
    temperature, and fan speed sensors:
On the LM87 monitor, AIN1 and AIN2 Volts DC sensors may replace either, or both
  of the FAN1 and FAN2 speed sensors, respectively.
The lmenv driver first appeared in
  OpenBSD 3.9. NetBSD support
  was added in NetBSD 7.0.
The lmenv driver was written for
  OpenBSD by Mark Kettenis
  ⟨kettenis@openbsd.org⟩, and ported to
  NetBSD by
Julian Coleman ⟨jdc@NetBSD.org⟩.
High and low sensor limits are not supported.
Interrupt support is not implemented.