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-SMBus Protocol Summary
-======================
-
-The following is a summary of the SMBus protocol. It applies to
-all revisions of the protocol (1.0, 1.1, and 2.0).
-Certain protocol features which are not supported by
-this package are briefly described at the end of this document.
-
-Some adapters understand only the SMBus (System Management Bus) protocol,
-which is a subset from the I2C protocol. Fortunately, many devices use
-only the same subset, which makes it possible to put them on an SMBus.
-
-If you write a driver for some I2C device, please try to use the SMBus
-commands if at all possible (if the device uses only that subset of the
-I2C protocol). This makes it possible to use the device driver on both
-SMBus adapters and I2C adapters (the SMBus command set is automatically
-translated to I2C on I2C adapters, but plain I2C commands can not be
-handled at all on most pure SMBus adapters).
-
-Below is a list of SMBus protocol operations, and the functions executing
-them. Note that the names used in the SMBus protocol specifications usually
-don't match these function names. For some of the operations which pass a
-single data byte, the functions using SMBus protocol operation names execute
-a different protocol operation entirely.
-
-
-Key to symbols
-==============
-
-S (1 bit) : Start bit
-P (1 bit) : Stop bit
-Rd/Wr (1 bit) : Read/Write bit. Rd equals 1, Wr equals 0.
-A, NA (1 bit) : Accept and reverse accept bit.
-Addr (7 bits): I2C 7 bit address. Note that this can be expanded as usual to
- get a 10 bit I2C address.
-Comm (8 bits): Command byte, a data byte which often selects a register on
- the device.
-Data (8 bits): A plain data byte. Sometimes, I write DataLow, DataHigh
- for 16 bit data.
-Count (8 bits): A data byte containing the length of a block operation.
-
-[..]: Data sent by I2C device, as opposed to data sent by the host adapter.
-
-
-SMBus Quick Command
-===================
-
-This sends a single bit to the device, at the place of the Rd/Wr bit.
-
-A Addr Rd/Wr [A] P
-
-
-SMBus Receive Byte: i2c_smbus_read_byte()
-==========================================
-
-This reads a single byte from a device, without specifying a device
-register. Some devices are so simple that this interface is enough; for
-others, it is a shorthand if you want to read the same register as in
-the previous SMBus command.
-
-S Addr Rd [A] [Data] NA P
-
-
-SMBus Send Byte: i2c_smbus_write_byte()
-========================================
-
-This operation is the reverse of Receive Byte: it sends a single byte
-to a device. See Receive Byte for more information.
-
-S Addr Wr [A] Data [A] P
-
-
-SMBus Read Byte: i2c_smbus_read_byte_data()
-============================================
-
-This reads a single byte from a device, from a designated register.
-The register is specified through the Comm byte.
-
-S Addr Wr [A] Comm [A] S Addr Rd [A] [Data] NA P
-
-
-SMBus Read Word: i2c_smbus_read_word_data()
-============================================
-
-This operation is very like Read Byte; again, data is read from a
-device, from a designated register that is specified through the Comm
-byte. But this time, the data is a complete word (16 bits).
-
-S Addr Wr [A] Comm [A] S Addr Rd [A] [DataLow] A [DataHigh] NA P
-
-Note the convenience function i2c_smbus_read_word_swapped is
-available for reads where the two data bytes are the other way
-around (not SMBus compliant, but very popular.)
-
-
-SMBus Write Byte: i2c_smbus_write_byte_data()
-==============================================
-
-This writes a single byte to a device, to a designated register. The
-register is specified through the Comm byte. This is the opposite of
-the Read Byte operation.
-
-S Addr Wr [A] Comm [A] Data [A] P
-
-
-SMBus Write Word: i2c_smbus_write_word_data()
-==============================================
-
-This is the opposite of the Read Word operation. 16 bits
-of data is written to a device, to the designated register that is
-specified through the Comm byte.
-
-S Addr Wr [A] Comm [A] DataLow [A] DataHigh [A] P
-
-Note the convenience function i2c_smbus_write_word_swapped is
-available for writes where the two data bytes are the other way
-around (not SMBus compliant, but very popular.)
-
-
-SMBus Process Call: i2c_smbus_process_call()
-=============================================
-
-This command selects a device register (through the Comm byte), sends
-16 bits of data to it, and reads 16 bits of data in return.
-
-S Addr Wr [A] Comm [A] DataLow [A] DataHigh [A]
- S Addr Rd [A] [DataLow] A [DataHigh] NA P
-
-
-SMBus Block Read: i2c_smbus_read_block_data()
-==============================================
-
-This command reads a block of up to 32 bytes from a device, from a
-designated register that is specified through the Comm byte. The amount
-of data is specified by the device in the Count byte.
-
-S Addr Wr [A] Comm [A]
- S Addr Rd [A] [Count] A [Data] A [Data] A ... A [Data] NA P
-
-
-SMBus Block Write: i2c_smbus_write_block_data()
-================================================
-
-The opposite of the Block Read command, this writes up to 32 bytes to
-a device, to a designated register that is specified through the
-Comm byte. The amount of data is specified in the Count byte.
-
-S Addr Wr [A] Comm [A] Count [A] Data [A] Data [A] ... [A] Data [A] P
-
-
-SMBus Block Write - Block Read Process Call
-===========================================
-
-SMBus Block Write - Block Read Process Call was introduced in
-Revision 2.0 of the specification.
-
-This command selects a device register (through the Comm byte), sends
-1 to 31 bytes of data to it, and reads 1 to 31 bytes of data in return.
-
-S Addr Wr [A] Comm [A] Count [A] Data [A] ...
- S Addr Rd [A] [Count] A [Data] ... A P
-
-
-SMBus Host Notify
-=================
-
-This command is sent from a SMBus device acting as a master to the
-SMBus host acting as a slave.
-It is the same form as Write Word, with the command code replaced by the
-alerting device's address.
-
-[S] [HostAddr] [Wr] A [DevAddr] A [DataLow] A [DataHigh] A [P]
-
-
-Packet Error Checking (PEC)
-===========================
-
-Packet Error Checking was introduced in Revision 1.1 of the specification.
-
-PEC adds a CRC-8 error-checking byte to transfers using it, immediately
-before the terminating STOP.
-
-
-Address Resolution Protocol (ARP)
-=================================
-
-The Address Resolution Protocol was introduced in Revision 2.0 of
-the specification. It is a higher-layer protocol which uses the
-messages above.
-
-ARP adds device enumeration and dynamic address assignment to
-the protocol. All ARP communications use slave address 0x61 and
-require PEC checksums.
-
-
-SMBus Alert
-===========
-
-SMBus Alert was introduced in Revision 1.0 of the specification.
-
-The SMBus alert protocol allows several SMBus slave devices to share a
-single interrupt pin on the SMBus master, while still allowing the master
-to know which slave triggered the interrupt.
-
-This is implemented the following way in the Linux kernel:
-* I2C bus drivers which support SMBus alert should call
- i2c_setup_smbus_alert() to setup SMBus alert support.
-* I2C drivers for devices which can trigger SMBus alerts should implement
- the optional alert() callback.
-
-
-I2C Block Transactions
-======================
-
-The following I2C block transactions are supported by the
-SMBus layer and are described here for completeness.
-They are *NOT* defined by the SMBus specification.
-
-I2C block transactions do not limit the number of bytes transferred
-but the SMBus layer places a limit of 32 bytes.
-
-
-I2C Block Read: i2c_smbus_read_i2c_block_data()
-================================================
-
-This command reads a block of bytes from a device, from a
-designated register that is specified through the Comm byte.
-
-S Addr Wr [A] Comm [A]
- S Addr Rd [A] [Data] A [Data] A ... A [Data] NA P
-
-
-I2C Block Read (2 Comm bytes)
-=============================
-
-This command reads a block of bytes from a device, from a
-designated register that is specified through the two Comm bytes.
-
-S Addr Wr [A] Comm1 [A] Comm2 [A]
- S Addr Rd [A] [Data] A [Data] A ... A [Data] NA P
-
-
-I2C Block Write: i2c_smbus_write_i2c_block_data()
-==================================================
-
-The opposite of the Block Read command, this writes bytes to
-a device, to a designated register that is specified through the
-Comm byte. Note that command lengths of 0, 2, or more bytes are
-supported as they are indistinguishable from data.
-
-S Addr Wr [A] Comm [A] Data [A] Data [A] ... [A] Data [A] P