diff options
Diffstat (limited to 'Documentation/i2c/smbus-protocol')
| -rw-r--r-- | Documentation/i2c/smbus-protocol | 68 |
1 files changed, 57 insertions, 11 deletions
diff --git a/Documentation/i2c/smbus-protocol b/Documentation/i2c/smbus-protocol index 9df47441f0e..6012b12b351 100644 --- a/Documentation/i2c/smbus-protocol +++ b/Documentation/i2c/smbus-protocol @@ -23,6 +23,12 @@ 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. +Each transaction type corresponds to a functionality flag. Before calling a +transaction function, a device driver should always check (just once) for +the corresponding functionality flag to ensure that the underlying I2C +adapter supports the transaction in question. See +<file:Documentation/i2c/functionality> for the details. + Key to symbols ============== @@ -49,6 +55,8 @@ This sends a single bit to the device, at the place of the Rd/Wr bit. A Addr Rd/Wr [A] P +Functionality flag: I2C_FUNC_SMBUS_QUICK + SMBus Receive Byte: i2c_smbus_read_byte() ========================================== @@ -60,6 +68,8 @@ the previous SMBus command. S Addr Rd [A] [Data] NA P +Functionality flag: I2C_FUNC_SMBUS_READ_BYTE + SMBus Send Byte: i2c_smbus_write_byte() ======================================== @@ -69,6 +79,8 @@ to a device. See Receive Byte for more information. S Addr Wr [A] Data [A] P +Functionality flag: I2C_FUNC_SMBUS_WRITE_BYTE + SMBus Read Byte: i2c_smbus_read_byte_data() ============================================ @@ -78,6 +90,8 @@ The register is specified through the Comm byte. S Addr Wr [A] Comm [A] S Addr Rd [A] [Data] NA P +Functionality flag: I2C_FUNC_SMBUS_READ_BYTE_DATA + SMBus Read Word: i2c_smbus_read_word_data() ============================================ @@ -88,6 +102,12 @@ 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 +Functionality flag: I2C_FUNC_SMBUS_READ_WORD_DATA + +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() ============================================== @@ -98,6 +118,8 @@ the Read Byte operation. S Addr Wr [A] Comm [A] Data [A] P +Functionality flag: I2C_FUNC_SMBUS_WRITE_BYTE_DATA + SMBus Write Word: i2c_smbus_write_word_data() ============================================== @@ -108,9 +130,15 @@ specified through the Comm byte. S Addr Wr [A] Comm [A] DataLow [A] DataHigh [A] P +Functionality flag: I2C_FUNC_SMBUS_WRITE_WORD_DATA + +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() -============================================= +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. @@ -118,6 +146,8 @@ This command selects a device register (through the Comm byte), sends S Addr Wr [A] Comm [A] DataLow [A] DataHigh [A] S Addr Rd [A] [DataLow] A [DataHigh] NA P +Functionality flag: I2C_FUNC_SMBUS_PROC_CALL + SMBus Block Read: i2c_smbus_read_block_data() ============================================== @@ -129,6 +159,8 @@ 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 +Functionality flag: I2C_FUNC_SMBUS_READ_BLOCK_DATA + SMBus Block Write: i2c_smbus_write_block_data() ================================================ @@ -139,6 +171,8 @@ 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 +Functionality flag: I2C_FUNC_SMBUS_WRITE_BLOCK_DATA + SMBus Block Write - Block Read Process Call =========================================== @@ -152,6 +186,8 @@ This command selects a device register (through the Comm byte), sends S Addr Wr [A] Comm [A] Count [A] Data [A] ... S Addr Rd [A] [Count] A [Data] ... A P +Functionality flag: I2C_FUNC_SMBUS_BLOCK_PROC_CALL + SMBus Host Notify ================= @@ -185,6 +221,22 @@ 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 ====================== @@ -205,15 +257,7 @@ 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 +Functionality flag: I2C_FUNC_SMBUS_READ_I2C_BLOCK I2C Block Write: i2c_smbus_write_i2c_block_data() @@ -225,3 +269,5 @@ 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 + +Functionality flag: I2C_FUNC_SMBUS_WRITE_I2C_BLOCK |