ACPI/Board-EC interaction

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Documentation is now handled by the same processes we use for code: Add something to the Documentation/ directory in the coreboot repo, and it will be rendered to Contributions welcome!

This page details the required interface and implementation details for connecting embedded controller ASL files to mainboard ASL files. Implementing this specification is mandatory for every new mainboard/EC added to the tree.

EC ASL files should be self-contained, and not depend on the specific chipset or mainboard. As a result all variables and methods which are used must be standardized to foster interoperability and modularity. This specification details how to achieve those points.

System Resources

All ECs are assumed to use IO ports 0x62 and 0x66 for data/commands. If the EC also serves as a keyboard controller, it is assumed to use ports 0x60 and 0x64. I/O port accesses to these ports must be directed to the bus to which the EC is connected. These need not be individually documented.

If the EC uses different ports, or needs other system resources, those must be documented in src/ec/vendor/model/documentation.txt

Defined constants

    • The general purpose event (GPE) corresponding to the EC SCI line.

Hotkey and event methods

Provide a generic mainboard device in the \_SB scope with a set of pre-defined methods. This way, the EC can pass events to the mainboard for handling.

The mainboard is not required to implement all methods, however, it must provide all such methods for the EC. The EC can call any of these methods. If the EC requires a method which is not part of the standard set, the this fact must be documented src/ec/vendor/model/documentation.txt.

Device (MB) {
	/* Lid open */
	Method (LIDO) { /* Stub */ }
	/* Lid closed */
	Method (LIDC) { /* Stub */}
	/* Increase brightness */
	Method (BRTU) { /* Stub */ }
	/* Decrease brightness */
	Method (BRTD) { /* Stub */ }
 	/* Switch display */
	Method (DSPS) { /* Stub */ }
	/* Toggle wireless */
	Method (WLTG) { /* Stub */ }
	/* Decrease brightness */
	Method (LIDS) { /* Stub */ }

These methods should be called by the EC using the \_SB.MB scope:

/* Decrease brightness hotkey */
Method (_Q11, 0, NotSerialized)

EC-specific extensions

The EC may provide specific extensions to this specifications. However, any such extension must be fully documented in src/ec/vendor/model/documentation.txt. The EC must be able to function properly even if the mainboard does not define or use such extensions.