tis — TIS / FIFO MMIO transport

github.com/go-tpm2/tis is a pure-Go TPM TIS / FIFO MMIO transport. It drives the TCG PC Client TIS (FIFO) register handshake over the platform-provided common.Regs MMIO accessor and satisfies common.Transport, exchanging one fully-marshaled TPM 2.0 command buffer for the full response buffer. v0.1.0.

go get github.com/go-tpm2/tis

Usage

import (
    common "github.com/go-tpm2/common"
    "github.com/go-tpm2/tis"
)

// regs is your platform's MMIO window over the locality-0 register page
// (an mmap of /dev/mem at 0xFED4_0000, a hypervisor stub, a test fake…).
t, err := tis.Open(regs)
if err != nil {
    // no TPM present, or locality 0 could not be claimed
}

// *tis.TIS satisfies common.Transport — feed it to go-tpm2/tpm2:
//   tpm := tpm2.New(t); tpm.Startup(uint16(common.SUClear))

// …or send a raw command buffer:
rsp, err := t.Send(common.BuildCommand(uint16(common.TagNoSessions),
    uint32(common.CCGetRandom), []byte{0x00, 0x08}))

Scope

Open validates presence via TPM_DID_VID and claims locality 0 via the TPM_ACCESS handshake. Send runs the FIFO command sequence: move the TPM to Ready (STS.commandReady), stream the command into TPM_DATA_FIFO respecting burstCount and the Expect bit, start execution (STS.tpmGo), poll STS.dataAvail, read the 10-byte header to learn responseSize, drain the rest honoring burstCount, then release the locality. Every busy-wait is bounded and returns a typed error.

Authority

Register offsets, bit fields, and the command sequence follow the TCG PC Client Platform TPM Profile (PTP) Specification, "FIFO Interface" chapter (which folds in the legacy TCG PC Client Specific TPM Interface Specification (TIS) 1.3). The TPM payloads are big-endian per the TCG TPM 2.0, Part 1 (via common); the TIS control registers are native-endian MMIO via common.Regs. Each register/bit is cited at its definition in regs.go and each handshake step in tis.go. The two driver-side safety values (the spin budget and the response cap) are marked INFERRED: — and confirmed against a live swtpm by validate (cmd/tpmvalidate-tis).

Conventions

Pure Go, CGO_ENABLED=0, no architecture-specific assembly, big-endian TPM wire (via common), GOWORK=off, BSD-3-Clause on every file, 100% statement coverage.