EC Services Architecture

Communication Pathways

flowchart TD
    A[Host OS or Firmware]
    B[ACPI Interface / Mailbox / HID]
    C[EC Service Dispatcher]
    D[Subsystem Controller - Battery, Thermal, etc.]

    A --> B
    B --> C
    C --> D

Figure: EC Service Entry Points Host platforms interact with EC services through one or more communication pathways. These may include ACPI-defined regions, mailbox protocols, or vendor-defined HID messages. The EC processes these via service dispatch logic.

Messaging Exchange Format (Conceptual)

sequenceDiagram
    participant Host
    participant EC

    Host->>EC: Request {Service ID, Command, Payload}
    EC-->>Host: Response {Status, Data}
  

Figure: Message Exchange

The diagram above illustrates the basic message handshake.

This table explains the field data exchanged:

Field	Description
Service ID	Identifies target subsystem
Command	Specific operation to perform
Payload	Data required for operation
Status	Result of operation
Data	Optional result values

Secure and Non-Secure Implementations

In the diagram below, the dark blue sections are those elements that are part of normal (non-secure) memory space and may be called from a service interface directly. As we can see on the Non-Secure side, the ACPI transport channel has access to the EC component implementations either directly or through the FF-A (Firmware Framework Memory Management Protocol).

Secure implementation architecture can be seen in the upcoming Security discussion.

flowchart TD
    A[Untrusted Host OS]
    B[Trusted Runtime Services]
    C[EC Service Gateway]
    D[EC Subsystems]

    A -.->|Filtered Access| C
    B -->|Secure Channel| C
    C --> D