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author | Linus Torvalds <torvalds@ppc970.osdl.org> | 2005-04-17 00:20:36 +0200 |
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committer | Linus Torvalds <torvalds@ppc970.osdl.org> | 2005-04-17 00:20:36 +0200 |
commit | 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch) | |
tree | 0bba044c4ce775e45a88a51686b5d9f90697ea9d /Documentation/i2c/i2c-stub | |
download | linux-1da177e4c3f41524e886b7f1b8a0c1fc7321cac2.tar.xz linux-1da177e4c3f41524e886b7f1b8a0c1fc7321cac2.zip |
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 @@ +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. + |