Commit | Line | Data |
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1da177e4 LT |
1 | MODULE: i2c-stub |
2 | ||
3 | DESCRIPTION: | |
4 | ||
5 | This module is a very simple fake I2C/SMBus driver. It implements four | |
6 | types of SMBus commands: write quick, (r/w) byte, (r/w) byte data, and | |
7 | (r/w) word data. | |
8 | ||
9 | No hardware is needed nor associated with this module. It will accept write | |
10 | quick commands to all addresses; it will respond to the other commands (also | |
11 | to all addresses) by reading from or writing to an array in memory. It will | |
12 | also spam the kernel logs for every command it handles. | |
13 | ||
14 | A pointer register with auto-increment is implemented for all byte | |
15 | operations. This allows for continuous byte reads like those supported by | |
16 | EEPROMs, among others. | |
17 | ||
18 | The typical use-case is like this: | |
19 | 1. load this module | |
20 | 2. use i2cset (from lm_sensors project) to pre-load some data | |
21 | 3. load the target sensors chip driver module | |
22 | 4. observe its behavior in the kernel log | |
23 | ||
24 | CAVEATS: | |
25 | ||
26 | There are independent arrays for byte/data and word/data commands. Depending | |
27 | on if/how a target driver mixes them, you'll need to be careful. | |
28 | ||
29 | If your target driver polls some byte or word waiting for it to change, the | |
30 | stub could lock it up. Use i2cset to unlock it. | |
31 | ||
32 | If the hardware for your driver has banked registers (e.g. Winbond sensors | |
33 | chips) this module will not work well - although it could be extended to | |
34 | support that pretty easily. | |
35 | ||
36 | If you spam it hard enough, printk can be lossy. This module really wants | |
37 | something like relayfs. | |
38 |