Difference between revisions of "DSDT (简体中文)"

From ArchWiki
Jump to: navigation, search
(No difference)

Revision as of 08:14, 14 June 2018

DSDT(Differentiated System Description Table)是ACPI规格的一部分。它提供了关于一个给定系统中受支持的电源事项的信息。ACPI表是由制造商提供在固件里的。通常,Linux遇到的问题是确实某些ACPI功能,比如风扇不转,盖子合上时屏幕不熄灭等等。这些问题可以归咎于DSDT是为Windows所特制的。安装后可以打补丁来修复这种情况。这篇文章的目标是分析并且重建一个有错误的DSDT,这样内核就会略过默认的DSDT。


Note: Linux ACPI项目的目标是Linux应该可以工作在未修改的固件上。如果你仍然觉得这种方法在现代内核上是必要的,那么你应该考虑一下报告bug


  • 很有可能硬件制造商已经发布了一个修复了ACPI相关问题的固件更新。安装一个升级后的固件通常是一个比这个方法更好的选择,因为这会避免重复的工作。
  • 这个过程会篡改你系统上一些相当基础的代码。你要对你要做出的改动相当确信。你可能还会想在行动之前先备份你的硬盘
  • 即使在你尝试你自行修复你的DSDT之前,你也可以尝试一些不同的捷径:



 acpi_os_name="Microsoft Windows NT"





  • "Microsoft Windows XP"
  • "Microsoft Windows 2000"
  • "Microsoft Windows 2000.1"
  • "Microsoft Windows ME: Millennium Edition"
  • "Windows 2001"
  • "Windows 2006"
  • "Windows 2009"
  • "Windows 2012"
  • 当这些都失败时,你可以尝试"Linux"

出于好奇,你可以执行下面的步骤来提取你的DSDT并找到.dsl文件。你只需grep Windows然后看看出现了什么。

Find a fixed DSDT

A DSDT file is originally written in ACPI Source language (an .asl/.dsl file). Using a compiler this can produce an 'ACPI Machine Language' file (.aml) or a hex table (.hex). To incorporate the file in your Arch install, you will need to get hold of a compiled .aml file. - whether this means compiling it yourself or trusting some stranger on the Internet is at your discretion. If you do download a file from the world wide web, it will most likely be a compressed .asl file. So you will need to unzip it and compile it. The upside to this is that you won't have to research specific code fixes yourself.

Arch users with the same laptop as you are: a minority of a minority of a minority. Try browsing other distro/linux forums for talk about the same model. Likelihood is that they have the same problems and either because there is a lot of them, or because they're tech savvy -- someone there has produced a working DSDT and maybe even provides a precompiled version (again, use at your own risk). Search engines are your best tools. Try keeping it short: 'model name' + 'dsdt' will probably produce results.

Recompiling it yourself

Your best resources in this endeavor are going to be ACPI Spec homepage, and Linux ACPI Project which supercedes the activity that occurred at acpi.sourceforge.net. In a nutshell, you can use Intel's ASL compiler to turn your systems DSDT table into source code, locate/fix the errors, and recompile.

You'll need to install iasl[broken link: replaced by acpica] to modify code.

What compiled the original code? Check if your system's DSDT was compiled using Intel or Microsoft compiler:

 $ dmesg|grep DSDT 
ACPI: DSDT 00000000bf7e5000 0A35F (v02 Intel  CALPELLA 06040000 INTL 20060912)
ACPI: EC: Look up EC in DSDT

In case Microsoft's compiler had been used, abbreviation INTL would instead be MSFT. In the example, there were 5 errors on decompiling/recompiling the DSDT. Two of them were easy to fix after a bit of googling and delving into the ACPI specification. Three of them were due to different versions of compiler used and are, as later discovered, handled by the ACPICA at boot-time. The ACPICA component of the kernel can handle most of the trivial errors you get while compiling the DSDT. So do not fret yourself over compile errors if your system is working the way it should.

1.) Extract ACPI tables (as root): # cat /sys/firmware/acpi/tables/DSDT > dsdt.dat

2.) Decompile: iasl -d dsdt.dat

3.) Recompile: iasl -tc dsdt.dsl

4.) Examine errors and fix. e.g.:
dsdt.dsl   6727:                         Name (_PLD, Buffer (0x10)  
Error    4105 -          Invalid object type for reserved name ^  (found BUFFER, requires Package) 
 nano +6727 dsdt.dsl
(_PLD, Package(1) {Buffer (0x10)...

5.) Increase OEM version or otherwise the kernel will not apply the modified ACPI table. For example, before modification:

DefinitionBlock ("DSDT.aml", "DSDT", 2, "INTEL ", "TEMPLATE", 0x00000000)

After modification:

DefinitionBlock ("DSDT.aml", "DSDT", 2, "INTEL ", "TEMPLATE", 0x00000001)

6.) Compile fixed code: iasl -tc dsdt.dsl (Might want to try option -ic for C include file to insert into kernel source)

If it says no errors and no warnings you should be good to go.

Using modified code

Warning: After each BIOS update you will need to fix DSDT again and repeat these steps!

There are at least two ways to use a custom DSDT:

  • creating a CPIO archive that is loaded by the bootloader
  • compiling it into the kernel

Using a CPIO archive

This method has the advantage that you do not need to recompile your kernel, and updating the kernel will not make it necessary to repeat these steps.

This method requires the ACPI_TABLE_UPGRADE=y kernel config to be enabled (true for the linux package). See [1] for details.

First, create the following folder structure:

$ mkdir -p kernel/firmware/acpi

Copy the fixed ACPI tables into the just created kernel/firmware/acpi folder, for example:

$ cp dsdt.aml ssdt1.aml kernel/firmware/acpi

Within the same folder where the newly created kernel/ folder resides, run:

$ find kernel | cpio -H newc --create > acpi_override

This creates the CPIO archive containing the fixed ACPI tables. Copy the archive to the boot directory.

# cp acpi_override /boot

Lastly, configure the bootloader to load your CPIO archive. For example, using Systemd-boot, /boot/loader/entries/arch.conf might look like this:

title	 Arch Linux
linux	 /vmlinuz-linux
initrd   /acpi_override
initrd	 /initramfs-linux.img
options  root=PARTUUID=ec9d5998-a9db-4bd8-8ea0-35a45df04701 resume=PARTUUID=58d0aa86-d39b-4fe1-81cf-45e7add275a0 ...

Now all that is left to do is to reboot and to verify the result.

Compiling into the kernel

You'll want to be familiar with compiling your own kernel. The most straightforward way is with the "traditional" approach. After compiling DSDT, iasl produce two files: dsdt.hex and dsdt.aml.

Using menuconfig:

  • Disable "Select only drivers that don't need compile-time external firmware". Located in "Device Drivers -> Generic Driver Options".
  • Enable "Include Custom DSDT" and specify the absolute path of your fixed DSDT file (dsdt.hex, not dsdt.aml). Located in "Power management and ACPI options -> ACPI (Advanced Configuration and Power Interface) Support".

Verify successful override

  1. Run dmesg | grep ACPI.
  2. Look for clues that suggest an override, for example:
[    0.000000] ACPI: Override [DSDT-   A M I], this is unsafe: tainting kernel
[    0.000000] ACPI: DSDT 00000000be9b1190 Logical table override, new table: ffffffff81865af0
[    0.000000] ACPI: DSDT ffffffff81865af0 0BBA3 (v02 ALASKA    A M I 000000F3 INTL 20130517)

See also