piixpm —
Intel PIIX and compatible Power Management controller
piixpm* at pci? dev ? function ?
iic* at piixpm?
The piixpm driver provides support for the Intel PIIX
  and compatible Power Management controller. Only the SMBus host interface is
  supported and can be used with the
  iic(4) framework.
Supported chipsets:
  - ATI SB200, SB300, SB400, SB600, SB700, SB800
- Intel 82371AB (PIIX4), 82440MX
- Serverworks OSB4, OSB5, OSB6, HT1000SB
- AMD FCHs (HUDSON, BOLTON and KERNCZ)
Thepiixpm driver first appeared in
  OpenBSD 3.9 and then in NetBSD
  4.0.
The driver doesn't support I2C commands with a data buffer size of more than 2
  bytes.