Shutdown: Difference between revisions
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* Perform an installation check.
* Check if the APM version is '''at least''' 1.1
* Disconnect any existing APM interface.
* Connect the Real Mode interface.
* Tell the APM that your driver supports version 1.1
* Enable power management for all devices.
* Set the power state for all devices to "Off" (03h).
If the APM version is 1.0 (or the APM isn't told that your code supports version 1.1, so it will run as 1.0 for legacy purposes) it isn't possible to set the power state for all devices (maybe it's possible to shut each device down individually)
== ACPI ==
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The ACPI shutdown is technically a really simple thing all that is needed is a <code>outw(PM1a_CNT, SLP_TYPa | SLP_EN );</code> and the computer is powered off. The problem lies in the gathering of these values especialy since the <code>SLP_TYPa</code> is in the <code>\_S5</code> object which is in the <code>DSDT</code> and therefore AML encoded.
</blockquote>
'''Warning:''' the code above shouldn't be used in production. There are many things the author skips, like calling the _PTS method. A real AML interpreter is required for that, like for example, ACPICA.
On many hardware calling _PTS is required and failing to call it will cause shutdown to fail, or cause hw to freeze in some half-shutdown phase. This phenomenon mostly occurs on laptops, but also occurs on desktops.
== Emulator-specific methods ==
In some cases (such as testing), you may want a poweroff method, but not need it to work on real hardware.
In Bochs, and older versions of QEMU(than 2.0), you can do the following:
<syntaxhighlight lang="c">
outw(0xB004, 0x2000);
</syntaxhighlight>
In newer versions of QEMU, you can do shutdown with:
<syntaxhighlight lang="c">
outw(0x604, 0x2000);
</syntaxhighlight>
In Virtualbox, you can do shutdown with:
<syntaxhighlight lang="c">
outw(0x4004, 0x3400);
</syntaxhighlight>
In Cloud Hypervisor, you can do shutdown with:
<syntaxhighlight lang="c">
outw(0x600, 0x34);
</syntaxhighlight>
== See Also ==
=== Articles ===
* [[Reboot]]
[[Category:Power management]]
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