diff options
| author | Linus Torvalds <torvalds@ppc970.osdl.org> | 2005-04-16 18:20:36 -0400 |
|---|---|---|
| committer | Linus Torvalds <torvalds@ppc970.osdl.org> | 2005-04-16 18:20:36 -0400 |
| commit | 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch) | |
| tree | 0bba044c4ce775e45a88a51686b5d9f90697ea9d /Documentation/i2c/i2c-stub | |
Linux-2.6.12-rc2v2.6.12-rc2
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
Diffstat (limited to 'Documentation/i2c/i2c-stub')
| -rw-r--r-- | Documentation/i2c/i2c-stub | 38 |
1 files changed, 38 insertions, 0 deletions
diff --git a/Documentation/i2c/i2c-stub b/Documentation/i2c/i2c-stub new file mode 100644 index 000000000000..d6dcb138abf5 --- /dev/null +++ b/Documentation/i2c/i2c-stub | |||
| @@ -0,0 +1,38 @@ | |||
| 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 | |||
