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1 | MODULE: i2c-stub |
2 | |
3 | DESCRIPTION: |
4 | |
5 | This module is a very simple fake I2C/SMBus driver. It implements five |
6 | types of SMBus commands: write quick, (r/w) byte, (r/w) byte data, (r/w) |
7 | word data, and (r/w) I2C block data. |
8 | |
9 | You need to provide chip addresses as a module parameter when loading this |
10 | driver, which will then only react to SMBus commands to these addresses. |
11 | |
12 | No hardware is needed nor associated with this module. It will accept write |
13 | quick commands to the specified addresses; it will respond to the other |
14 | commands (also to the specified addresses) by reading from or writing to |
15 | arrays in memory. It will also spam the kernel logs for every command it |
16 | handles. |
17 | |
18 | A pointer register with auto-increment is implemented for all byte |
19 | operations. This allows for continuous byte reads like those supported by |
20 | EEPROMs, among others. |
21 | |
22 | The typical use-case is like this: |
23 | 1. load this module |
24 | 2. use i2cset (from the i2c-tools project) to pre-load some data |
25 | 3. load the target chip driver module |
26 | 4. observe its behavior in the kernel log |
27 | |
28 | There's a script named i2c-stub-from-dump in the i2c-tools package which |
29 | can load register values automatically from a chip dump. |
30 | |
31 | PARAMETERS: |
32 | |
33 | int chip_addr[10]: |
34 | The SMBus addresses to emulate chips at. |
35 | |
36 | unsigned long functionality: |
37 | Functionality override, to disable some commands. See I2C_FUNC_* |
38 | constants in <linux/i2c.h> for the suitable values. For example, |
39 | value 0x1f0000 would only enable the quick, byte and byte data |
40 | commands. |
41 | |
42 | CAVEATS: |
43 | |
44 | If your target driver polls some byte or word waiting for it to change, the |
45 | stub could lock it up. Use i2cset to unlock it. |
46 | |
47 | If the hardware for your driver has banked registers (e.g. Winbond sensors |
48 | chips) this module will not work well - although it could be extended to |
49 | support that pretty easily. |
50 | |
51 | If you spam it hard enough, printk can be lossy. This module really wants |
52 | something like relayfs. |
53 | |
54 |
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Tags:
od-2011-09-04
od-2011-09-18
v2.6.34-rc5
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