TCG PC Client Physical Presence Interface Specification
The Physical Presence Interface utilizes the industry-standard Advanced Configuration and Power Interface (ACPI) to provide a communication mechanism between the OS and the BIOS, enabling the OS and the BIOS to cooperate to provide a simple and straightforward platform user experience for administering the TPM without sacrificing security.
This Interface was designed under the assumption that TPM commands requiring physical presence should only be executable in the pre-OS environment. Given this constraint, the Physical Presence Interface eases administration by minimizing the need to understand and configure a platform’s BIOS — a significant deterrent to the mass deployment of trusted platforms, especially across heterogeneous platforms.
The implementation of the Physical Presence Interface is highly recommended for platforms that support the software method of asserting physical presence (as indicated by the physicalPresenceCMDEnable permanent flag of the TPM).