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authorLinus Torvalds <torvalds@linux-foundation.org>2012-05-30 19:03:46 +0200
committerLinus Torvalds <torvalds@linux-foundation.org>2012-05-30 19:03:46 +0200
commit42fe55ce905212542426fa6407a76534a5fb696a (patch)
tree874c5984e4222ea253b78c5be4755b3d31da54e2 /Documentation
parentMerge git://www.linux-watchdog.org/linux-watchdog (diff)
parenti2c: Split I2C_M_NOSTART support out of I2C_FUNC_PROTOCOL_MANGLING (diff)
downloadlinux-42fe55ce905212542426fa6407a76534a5fb696a.tar.xz
linux-42fe55ce905212542426fa6407a76534a5fb696a.zip
Merge branch 'i2c-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jdelvare/staging
Pull i2c updates from Jean Delvare. * 'i2c-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jdelvare/staging: i2c: Split I2C_M_NOSTART support out of I2C_FUNC_PROTOCOL_MANGLING i2c-dev: Add support for I2C_M_RECV_LEN
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/i2c/functionality9
-rw-r--r--Documentation/i2c/i2c-protocol9
2 files changed, 14 insertions, 4 deletions
diff --git a/Documentation/i2c/functionality b/Documentation/i2c/functionality
index 42c17c1fb3cd..b0ff2ab596ce 100644
--- a/Documentation/i2c/functionality
+++ b/Documentation/i2c/functionality
@@ -18,9 +18,9 @@ For the most up-to-date list of functionality constants, please check
adapters typically can not do these)
I2C_FUNC_10BIT_ADDR Handles the 10-bit address extensions
I2C_FUNC_PROTOCOL_MANGLING Knows about the I2C_M_IGNORE_NAK,
- I2C_M_REV_DIR_ADDR, I2C_M_NOSTART and
- I2C_M_NO_RD_ACK flags (which modify the
- I2C protocol!)
+ I2C_M_REV_DIR_ADDR and I2C_M_NO_RD_ACK
+ flags (which modify the I2C protocol!)
+ I2C_FUNC_NOSTART Can skip repeated start sequence
I2C_FUNC_SMBUS_QUICK Handles the SMBus write_quick command
I2C_FUNC_SMBUS_READ_BYTE Handles the SMBus read_byte command
I2C_FUNC_SMBUS_WRITE_BYTE Handles the SMBus write_byte command
@@ -50,6 +50,9 @@ A few combinations of the above flags are also defined for your convenience:
emulated by a real I2C adapter (using
the transparent emulation layer)
+In kernel versions prior to 3.5 I2C_FUNC_NOSTART was implemented as
+part of I2C_FUNC_PROTOCOL_MANGLING.
+
ADAPTER IMPLEMENTATION
----------------------
diff --git a/Documentation/i2c/i2c-protocol b/Documentation/i2c/i2c-protocol
index 10518dd58814..0b3e62d1f77a 100644
--- a/Documentation/i2c/i2c-protocol
+++ b/Documentation/i2c/i2c-protocol
@@ -49,7 +49,9 @@ a byte read, followed by a byte write:
Modified transactions
=====================
-We have found some I2C devices that needs the following modifications:
+The following modifications to the I2C protocol can also be generated,
+with the exception of I2C_M_NOSTART these are usually only needed to
+work around device issues:
Flag I2C_M_NOSTART:
In a combined transaction, no 'S Addr Wr/Rd [A]' is generated at some
@@ -60,6 +62,11 @@ We have found some I2C devices that needs the following modifications:
we do not generate Addr, but we do generate the startbit S. This will
probably confuse all other clients on your bus, so don't try this.
+ This is often used to gather transmits from multiple data buffers in
+ system memory into something that appears as a single transfer to the
+ I2C device but may also be used between direction changes by some
+ rare devices.
+
Flags I2C_M_REV_DIR_ADDR
This toggles the Rd/Wr flag. That is, if you want to do a write, but
need to emit an Rd instead of a Wr, or vice versa, you set this