diff options
Diffstat (limited to 'Documentation/i2c')
| -rw-r--r-- | Documentation/i2c/smbus-protocol | 40 |
1 files changed, 31 insertions, 9 deletions
diff --git a/Documentation/i2c/smbus-protocol b/Documentation/i2c/smbus-protocol index 49f5b680809d..d1f22618e14b 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 +102,8 @@ 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.) @@ -102,6 +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() ============================================== @@ -112,6 +130,8 @@ 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.) @@ -126,6 +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() ============================================== @@ -137,6 +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() ================================================ @@ -147,6 +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 =========================================== @@ -160,6 +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 ================= @@ -229,15 +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() @@ -249,3 +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 |