SMBus target and host

SMBus target

Read/write protcols defined in SMBus spec rev. 3 are implemented with the help of I2C target driver in Zephyr. General rules are

• Read commands and process call commands require instant preparation of response within interrupt handler of (restart) read event.
• Write commands are processed in a worker thread after stop event, which allow heavy duties to be executed. In the meantime, a status byte can be retrieved by host for checking result of the last command.
• Write commands can try waking up previous unresponsive command. This is usually done by a dummy command that does nothing.
• Command 0xFE is reserved for enhanced special write.
• Command 0xFF is reserved for enhanced special read.

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SMBus and PMBus host

The SMBus host controller uses i2c driver instead of smbus driver, and implements

• Write Byte/Word
• Read Byte/Word
• Process Call
• Block Write/Read
• Write 32 Protocol
• Read 32 Protocol
• Write 64 Protocol
• Read 64 Protocol

Generic PMBus host controller with limited register list is implemented.