Ubuntu Wiki

Summary

This page is going to tell how to read DSDT/SSDT table and how it affects your system.

Overview of ACPI

*TBD*

Dump DSDT/SSDT

There are many ways to dump ACPI tables. The most easy way is to select and read out tables file from /sys/firmware/acpi/tables

user@here:~$ tree /sys/firmware/acpi/tables/
/sys/firmware/acpi/tables/
|-- APIC
|-- ATKG
|-- BOOT
|-- DBGP
|-- DSDT
|-- ECDT
|-- FACP
|-- FACS
|-- HPET
|-- MCFG
|-- OEMB
|-- SLIC
|-- SSDT
`-- dynamic
    |-- SSDT2
    |-- SSDT3
    |-- SSDT4
    `-- SSDT5

1 directory, 17 files

You can copy files out with root privilege and use iasl to decompile it

user@here:~$ sudo cp /sys/firmware/acpi/tables/DSDT ~/DSDT.bin
user@here:~$ sudo chown ikepanhc:ikepanhc /home/ikepanhc/DSDT.bin
user@here:~$ iasl -d ~/DSDT.bin 

Intel ACPI Component Architecture
AML Disassembler version 20090521 [Jun 30 2009]
Copyright (C) 2000 - 2009 Intel Corporation
Supports ACPI Specification Revision 3.0a

Loading Acpi table from file /home/user/DSDT.bin
Acpi table [DSDT] successfully installed and loaded
Pass 1 parse of [DSDT]
Pass 2 parse of [DSDT]
Parsing Deferred Opcodes (Methods/Buffers/Packages/Regions)
............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................
Parsing completed
Disassembly completed, written to "/home/user/DSDT.dsl"

Information from /sys

There are lots of ACPI devices described in DSDT/SSDT. DSDT/SSDT describes them in a tree form.

user@here:~$ tree /sys/devices/LNXSYSTM\:00/
/sys/devices/LNXSYSTM:00/
|-- LNXCPU:00
|-- LNXCPU:01
|-- LNXPWRBN:00
|-- LNXTHERM:00
|   `-- LNXTHERM:01
`-- device:00
    |-- ATK0101:00
    |-- PNP0A08:00
    |   |-- ACPI0003:00
    |   |-- PNP0C02:00
    |   |-- PNP0C02:05
    |   |-- PNP0C0A:00
    |   |-- device:01
    |   |   |-- LEN0013:00
    |   |   |-- PNP0000:00
    |   |   |-- PNP0100:00
    |   |   |-- PNP0103:00
    |   |   |-- PNP0200:00
    |   |   |-- PNP0303:00
    |   |   |-- PNP0800:00
    |   |   |-- PNP0B00:00
    |   |   |-- PNP0C02:01
    |   |   |-- PNP0C02:02
    |   |   |-- PNP0C02:03
    |   |   |-- PNP0C02:04
    |   |   |-- PNP0C04:00
    |   |   `-- PNP0C09:00
    |   |       `-- LEN0014:00
    |   |-- device:02
    |   |   |-- device:03
    |   |   |   |-- device:04
    |   |   |   `-- device:05
    |   |   |-- device:06
    |   |   |   |-- device:07
    |   |   |   `-- device:08
    |   |   |-- device:09
    |   |   |-- device:0a
    |   |   |-- device:0b
    |   |   `-- device:0c
    |   |-- device:0d
    |   |-- device:0e
    |   |-- device:0f
    |   |-- device:10
    |   |-- device:11
    |   |-- device:12
    |   |-- device:13
    |   |   `-- device:14
    |   |       |-- device:15
    |   |       `-- device:16
    |   |-- device:17
    |   |-- device:18
    |   |-- device:19
    |   |-- device:1a
    |   |-- device:1b
    |   |   |-- device:1c
    |   |   |-- device:1d
    |   |   `-- device:1e
    |   |-- device:1f
    |   |   `-- device:20
    |   |       |-- device:21
    |   |       |-- device:22
    |   |       `-- device:23
    |   |-- device:24
    |   |-- device:25
    |   |   `-- device:26
    |   |-- device:27
    |   |   |-- device:28
    |   |   |-- device:29
    |   |   |-- device:2a
    |   |   |-- device:2b
    |   |   |-- device:2c
    |   |   |-- device:2d
    |   |   `-- device:2e
    |   |-- device:2f
    |   |   `-- device:30
    |   `-- device:31
    |       |-- device:32
    |       `-- device:33
    |-- PNP0C01:00
    |-- PNP0C0D:00
    |-- PNP0C0E:00
    |-- PNP0C0F:00
    |-- PNP0C0F:01
    |-- PNP0C0F:02
    |-- PNP0C0F:03
    |-- PNP0C0F:04
    |-- PNP0C0F:05
    |-- PNP0C0F:06
    `-- PNP0C0F:07

The folder name starts with "device" means that this device has no HID (Hardware ID). It's hard to bind a driver on it and execute its method, so we will ignore them.
The folder name starts with "PNP" or "ACPI" means that this device is generic ACPI device, not a machine specific device. When we are going to enable some special function, its not necessary to take a look.

Read DSDT/SSDT