i2c-acpi-sbus's Introduction

i2c-acpi-sbus

ACPI SBUS i2c device driver.

The SBUS ACPI device implements an SMBus device, slightly simplified from the similar device implemented by the i2c-i801 driver. I could not find any documentation but the supported methods are straightforward to understand:

SSXB - send byte
    Arg0: address << 1
    Arg1: data
    Return: 0 on failure, 1, on success

SRXB - receive byte
    Arg0: (address << 1) | 0x01

SWRB - write byte
    Arg0: address << 1
    Arg1: command
    Arg2: data
    Return: 0 on failure, 1, on success

SRDB - read byte
    Arg0: (address << 1) | 0x01
    Arg1: command
    Return: 0xffff on failure, the read byte otherwise

SWRW - write word
    Arg0: address << 1
    Arg1: command
    Arg2: data
    Return: 0 on failure, 1, on success

SRDW - read word
    Arg0: (address << 1) | 0x01
    Arg1: command
    Return: 0xffffffff on failure, the read word otherwise

SBLW - write block data
    Arg0: address << 1
    Arg1: command
    Arg2: data - data[0] is the number of bytes that follow
    Return: 0 on failure, 1, on success

SBLR - read block data
    Arg0: (address << 1) | 0x01
    Arg1: command
    Return: 0 on failure, the read data otherwise

When reading data, the ACPI code internally or's the address with 0x01, but to be safe this is done by the driver as well.

There seems to be no consensus on whether SWRW/SRDW are read in little-endian or big-endian, as both variants appear in the wild.

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