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-rw-r--r--Documentation/i2c/i2c-stub23
1 files changed, 17 insertions, 6 deletions
diff --git a/Documentation/i2c/i2c-stub b/Documentation/i2c/i2c-stub
index fa4b669c166b..a16924fbd289 100644
--- a/Documentation/i2c/i2c-stub
+++ b/Documentation/i2c/i2c-stub
@@ -2,9 +2,9 @@ MODULE: i2c-stub
DESCRIPTION:
-This module is a very simple fake I2C/SMBus driver. It implements five
+This module is a very simple fake I2C/SMBus driver. It implements six
types of SMBus commands: write quick, (r/w) byte, (r/w) byte data, (r/w)
-word data, and (r/w) I2C block data.
+word data, (r/w) I2C block data, and (r/w) SMBus block data.
You need to provide chip addresses as a module parameter when loading this
driver, which will then only react to SMBus commands to these addresses.
@@ -19,6 +19,14 @@ 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.
+SMBus block command support is disabled by default, and must be enabled
+explicitly by setting the respective bits (0x03000000) in the functionality
+module parameter.
+
+SMBus block commands must be written to configure an SMBus command for
+SMBus block operations. Writes can be partial. Block read commands always
+return the number of bytes selected with the largest write so far.
+
The typical use-case is like this:
1. load this module
2. use i2cset (from the i2c-tools project) to pre-load some data
@@ -39,15 +47,18 @@ unsigned long functionality:
value 0x1f0000 would only enable the quick, byte and byte data
commands.
+u8 bank_reg[10]
+u8 bank_mask[10]
+u8 bank_start[10]
+u8 bank_end[10]:
+ Optional bank settings. They tell which bits in which register
+ select the active bank, as well as the range of banked registers.
+
CAVEATS:
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.