Documentation/firmware-guide/acpi/i2c-muxes.rst

   1 .. SPDX-License-Identifier: GPL-2.0
   2
   3 ==============
   4 ACPI I2C Muxes
   5 ==============
   6
   7 Describing an I2C device hierarchy that includes I2C muxes requires an ACPI
   8 Device () scope per mux channel.
   9
  10 Consider this topology::
  11
  12     +------+   +------+
  13     | SMB1 |-->| MUX0 |--CH00--> i2c client A (0x50)
  14     |      |   | 0x70 |--CH01--> i2c client B (0x50)
  15     +------+   +------+
  16
  17 which corresponds to the following ASL::
  18
  19     Device (SMB1)
  20     {
  21         Name (_HID, ...)
  22         Device (MUX0)
  23         {
  24             Name (_HID, ...)
  25             Name (_CRS, ResourceTemplate () {
  26                 I2cSerialBus (0x70, ControllerInitiated, I2C_SPEED,
  27                             AddressingMode7Bit, "^SMB1", 0x00,
  28                             ResourceConsumer,,)
  29             }
  30
  31             Device (CH00)
  32             {
  33                 Name (_ADR, 0)
  34
  35                 Device (CLIA)
  36                 {
  37                     Name (_HID, ...)
  38                     Name (_CRS, ResourceTemplate () {
  39                         I2cSerialBus (0x50, ControllerInitiated, I2C_SPEED,
  40                                     AddressingMode7Bit, "^CH00", 0x00,
  41                                     ResourceConsumer,,)
  42                     }
  43                 }
  44             }
  45
  46             Device (CH01)
  47             {
  48                 Name (_ADR, 1)
  49
  50                 Device (CLIB)
  51                 {
  52                     Name (_HID, ...)
  53                     Name (_CRS, ResourceTemplate () {
  54                         I2cSerialBus (0x50, ControllerInitiated, I2C_SPEED,
  55                                     AddressingMode7Bit, "^CH01", 0x00,
  56                                     ResourceConsumer,,)
  57                     }
  58                 }
  59             }
  60         }
  61     }