7a8d29cec7
i2c-stub: Chip address as a module parameter Add a mandatory chip_addr parameter to i2c-stub. This parameter defines to which chip address the driver will respond, instead of reponding to all addresses as before. The idea is to prevent the users from loading i2c-stub at random and being then confused by the results of sensors-detect or other user-space tools. Signed-off-by: Jean Delvare <khali@linux-fr.org> Signed-off-by: Mark M. Hoffman <mhoffman@lightlink.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
50 lines
1.7 KiB
Plaintext
50 lines
1.7 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.
|
|
|
|
You need to provide a chip address as a module parameter when loading
|
|
this driver, which will then only react to SMBus commands to this address.
|
|
|
|
No hardware is needed nor associated with this module. It will accept write
|
|
quick commands to one address; it will respond to the other commands (also
|
|
to one address) 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
|
|
|
|
PARAMETERS:
|
|
|
|
int chip_addr:
|
|
The SMBus address to emulate a chip at.
|
|
|
|
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.
|
|
|
|
Only one chip address is supported - although this module could be
|
|
extended to support more.
|
|
|
|
If you spam it hard enough, printk can be lossy. This module really wants
|
|
something like relayfs.
|
|
|