23rd article: ACPI in Windows

The role of ACPI drivers in Windows has been unclear.

Do not even understand the role of the ACPI Protocol.

As a result, it was a preliminary understanding of ACPI to turn the 24th chapter in the "Beetle collection" and how to track ACPI code.

ACPI reports hardware information to the OS, while the OS controls the hardware through ACPI.

ACPI is a standard interface protocol between the OS and hardware/firmware.

ACPI uses ASL (ACPI SOURCE LANGUAGE) to describe the properties and methods of the system hardware, and ASL will eventually be compiled into the bytecode (bytecode) of the AML (ACPI Machine LANGUAGE).

After that, I looked through the contents of the WDK about ACPI:

ACPI devices include:

Low-level system devices such as batteries, thermal zones, and other devices defined in a system ' sACPI namespace.

The performance of ACPI devices in Windows drivers:

Definition block and one of its operation region.

An ACPI device was specified by a definition block in the ACPI System Description Tables. A device ' s definition block specifies, among other things, anoperationregion, which specifies a contiguous block of device memory that's used to access device data.

The Windows software for ACPI devices consists of:

1. ACPI System Driver Acpi.sys

2. WDM driver provided by vendor

3. ACPI BIOS, which is the so-called firmware

The process for this combination is: ACPI. SYS calls the operation region handler in the WDM driver provided by vendor to access the operation region to achieve the purpose of ACPI device data/control.

About the device stack:

The APCI device is integrated into the motherboard, the ACPI driver establishes the FDO, located under the fdo of the WDM driver, located above the PDO established by the root bus driver

If it is not integrated with the motherboard, ACPI establishes a PDO for the device, located under WDM-established FDO.

ACPI Control methods:

The so-called ACPI control method is the software that is described by Asl/aml to query and configure the hardware.

The ACPI driver is responsible for interpreting the execution.

Control methods is written in the ACPI Machine Language (AML), loaded from the system firmware into the ACPI namespace, a nd interpreted by the ACPI driver.

The naming rules for ACPI:

\ root of ACPI namespace
ABCD parent device (Indent once)
CHL1 child device of Abcd  (indent two times)
CHL2 child device of ABCD&NBSP ; (indented two times)
CHL3 child device of Chl2  (indent three times)
_foo control Method  (indent three times)
_foo control method  (indent once)

Windows names ACPI devices as objects (object), an object can include child objects, and an object can be either a child device or a control method.