mirror of
https://github.com/AuxXxilium/linux_dsm_epyc7002.git
synced 2024-12-05 14:16:39 +07:00
39 lines
1.4 KiB
Plaintext
39 lines
1.4 KiB
Plaintext
|
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.
|
||
|
|