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| author | Linus Torvalds <torvalds@linux-foundation.org> | 2012-05-30 10:03:46 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2012-05-30 10:03:46 -0700 |
| commit | 42fe55ce905212542426fa6407a76534a5fb696a (patch) | |
| tree | 874c5984e4222ea253b78c5be4755b3d31da54e2 /Documentation | |
| parent | 19ce0a995ff230b364c7329fd488c70e91c171d9 (diff) | |
| parent | 14674e70119ea01549ce593d8901a797f8a90f74 (diff) | |
| download | lwn-42fe55ce905212542426fa6407a76534a5fb696a.tar.gz lwn-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/functionality | 9 | ||||
| -rw-r--r-- | Documentation/i2c/i2c-protocol | 9 |
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 |