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- MODULE: i2c-stub
- DESCRIPTION:
- This module is a very simple fake I2C/SMBus driver. It implements four
- types of SMBus commands: write quick, (r/w) byte, (r/w) byte data, and
- (r/w) word data.
- No hardware is needed nor associated with this module. It will accept write
- quick commands to all addresses; it will respond to the other commands (also
- to all addresses) by reading from or writing to an array 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 lm_sensors project) to pre-load some data
- 3. load the target sensors chip driver module
- 4. observe its behavior in the kernel log
- CAVEATS:
- There are independent arrays for byte/data and word/data commands. Depending
- on if/how a target driver mixes them, you'll need to be careful.
- 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.
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