I2C / SMBus

The drivers

drivers/i2c/driver_i2c.c (the core) + driver_i2c_i801.c (the Intel SMBus controller) + driver_i2c_dw.c (DesignWare) + driver_smbus.c.

Commands

oc> i2cdetect    (bus scan)
oc> i2cget       (read a register)
oc> i2cset       (write a register)
oc> i2ctest      (bus self-test)
oc> smbus        (controller status)
oc> smbustest    (SMBus protocol test)

What rides on it

I2C HID devices (touchpads), RTC chips, and board-specific controllers - i2cdetect is always the first probe on real hardware.