xref: /linux/Documentation/firmware-guide/acpi/i2c-muxes.rst (revision c39f2d9db0fd81ea20bb5cce9b3f082ca63753e2) 
1.. SPDX-License-Identifier: GPL-2.0
2
3==============
4ACPI I2C Muxes
5==============
6
7Describing an I2C device hierarchy that includes I2C muxes requires an ACPI
8Device () scope per mux channel.
9
10Consider this topology::
11
12    +------+   +------+
13    | SMB1 |-->| MUX0 |--CH00--> i2c client A (0x50)
14    |      |   | 0x70 |--CH01--> i2c client B (0x50)
15    +------+   +------+
16
17which 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    }
62