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Diffstat (limited to 'Documentation/i2c/smbus-protocol.rst')
| -rw-r--r-- | Documentation/i2c/smbus-protocol.rst | 28 |
1 files changed, 15 insertions, 13 deletions
diff --git a/Documentation/i2c/smbus-protocol.rst b/Documentation/i2c/smbus-protocol.rst index c2e29633071e..adc87456c99d 100644 --- a/Documentation/i2c/smbus-protocol.rst +++ b/Documentation/i2c/smbus-protocol.rst @@ -27,8 +27,8 @@ 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 :doc:`functionality` for -the details. +adapter supports the transaction in question. See +Documentation/i2c/functionality.rst for the details. Key to symbols @@ -36,15 +36,17 @@ Key to symbols =============== ============================================================= S Start condition +Sr Repeated start condition, used to switch from write to + read mode. P Stop condition Rd/Wr (1 bit) Read/Write bit. Rd equals 1, Wr equals 0. A, NA (1 bit) Acknowledge (ACK) and Not Acknowledge (NACK) bit -Addr (7 bits) I2C 7 bit address. Note that this can be expanded as usual to +Addr (7 bits) I2C 7 bit address. Note that this can be expanded 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. +Data (8 bits) A plain data byte. DataLow and DataHigh represent the low and + high byte of a 16 bit word. 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 @@ -57,7 +59,7 @@ 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 + S Addr Rd/Wr [A] P Functionality flag: I2C_FUNC_SMBUS_QUICK @@ -100,7 +102,7 @@ Implemented by 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 + S Addr Wr [A] Comm [A] Sr Addr Rd [A] [Data] NA P Functionality flag: I2C_FUNC_SMBUS_READ_BYTE_DATA @@ -114,7 +116,7 @@ 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 + S Addr Wr [A] Comm [A] Sr Addr Rd [A] [DataLow] A [DataHigh] NA P Functionality flag: I2C_FUNC_SMBUS_READ_WORD_DATA @@ -164,7 +166,7 @@ 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 + Sr Addr Rd [A] [DataLow] A [DataHigh] NA P Functionality flag: I2C_FUNC_SMBUS_PROC_CALL @@ -181,7 +183,7 @@ 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 + Sr Addr Rd [A] [Count] A [Data] A [Data] A ... A [Data] NA P Functionality flag: I2C_FUNC_SMBUS_READ_BLOCK_DATA @@ -212,7 +214,7 @@ 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 + Sr Addr Rd [A] [Count] A [Data] ... A P Functionality flag: I2C_FUNC_SMBUS_BLOCK_PROC_CALL @@ -236,7 +238,7 @@ This is implemented in the following way in the Linux kernel: * I2C bus drivers trigger SMBus Host Notify by a call to i2c_handle_smbus_host_notify(). * I2C drivers for devices which can trigger SMBus Host Notify will have - client->irq assigned to a Host Notify IRQ if noone else specified an other. + client->irq assigned to a Host Notify IRQ if no one else specified another. There is currently no way to retrieve the data parameter from the client. @@ -300,7 +302,7 @@ 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 + Sr Addr Rd [A] [Data] A [Data] A ... A [Data] NA P Functionality flag: I2C_FUNC_SMBUS_READ_I2C_BLOCK |