MODULE: i2c-stub
  
  DESCRIPTION:

  This module is a very simple fake I2C/SMBus driver.  It implements five
  types of SMBus commands: write quick, (r/w) byte, (r/w) byte data, (r/w)
  word data, and (r/w) I2C block data.

  You need to provide chip addresses as a module parameter when loading this
  driver, which will then only react to SMBus commands to these addresses.

  No hardware is needed nor associated with this module.  It will accept write

  quick commands to the specified addresses; it will respond to the other
  commands (also to the specified addresses) by reading from or writing to
  arrays in memory.  It will also spam the kernel logs for every command it
  handles.

  
  A pointer register with auto-increment is implemented for all byte
  operations.  This allows for continuous byte reads like those supported by
  EEPROMs, among others.
  
  The typical use-case is like this:
  	1. load this module

  	2. use i2cset (from the i2c-tools project) to pre-load some data
  	3. load the target chip driver module

  	4. observe its behavior in the kernel log

  There's a script named i2c-stub-from-dump in the i2c-tools package which
  can load register values automatically from a chip dump.

  PARAMETERS:

  int chip_addr[10]:
  	The SMBus addresses to emulate chips at.

  unsigned long functionality:
  	Functionality override, to disable some commands. See I2C_FUNC_*
  	constants in <linux/i2c.h> for the suitable values. For example,
  	value 0x1f0000 would only enable the quick, byte and byte data
  	commands.

  CAVEATS:

  If your target driver polls some byte or word waiting for it to change, the
  stub could lock it up.  Use i2cset to unlock it.
  
  If the hardware for your driver has banked registers (e.g. Winbond sensors
  chips) this module will not work well - although it could be extended to
  support that pretty easily.
  
  If you spam it hard enough, printk can be lossy.  This module really wants
  something like relayfs.