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diff --git a/Documentation/i2c/smbus-protocol b/Documentation/i2c/smbus-protocol deleted file mode 100644 index 49f5b680809..00000000000 --- a/Documentation/i2c/smbus-protocol +++ /dev/null @@ -1,251 +0,0 @@ -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 |