summaryrefslogtreecommitdiff
path: root/Documentation/i2c/i2c-stub
diff options
context:
space:
mode:
authorLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 15:20:36 -0700
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 15:20:36 -0700
commit1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch)
tree0bba044c4ce775e45a88a51686b5d9f90697ea9d /Documentation/i2c/i2c-stub
downloadconfigs-1da177e4c3f41524e886b7f1b8a0c1fc7321cac2.tar.gz
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-stub38
1 files changed, 38 insertions, 0 deletions
diff --git a/Documentation/i2c/i2c-stub b/Documentation/i2c/i2c-stub
new file mode 100644
index 00000000000..d6dcb138abf
--- /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.
+