i2c: stub: Add support for SMBus block commands

SMBus block commands are different to I2C block commands since
the returned data is not normally accessible with byte or word
commands on other command offsets. Add linked list of 'block'
commands to support those commands.

Access mechanism is quite simple: Block commands must be written
before they can be read. Subsequent writes can be partial. Block
read commands always return the number of bytes associated with
the longest previous write.

Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: Jean Delvare <jdelvare@suse.de>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

1 files changed, 10 insertions, 2 deletions

diff --git a/Documentation/i2c/i2c-stub b/Documentation/i2c/i2c-stub
index fa4b669c166b..a0fe7a04a3bd 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