sysclasstpm

sysclasstpm is the Linux kernel sysfs class that exposes Trusted Platform Module (TPM) hardware and drivers to user space. It provides a stable, unified interface for TPM devices that may implement different TPM specifications (such as TPM 1.2 or TPM 2.0) and come from various manufacturers. The class allows software to discover TPM devices, inspect their state, and relate them to the corresponding character devices used for command/response I/O.

In sysfs, TPM devices appear under the /sys/class/tpm directory, with individual devices typically named tpm0, tpm1, etc. Each device entry exposes attributes describing identification, capabilities, and status, and is linked to the kernel TPM driver stack. Userspace tooling can access the TPM via the associated character devices (for example /dev/tpm0) and, on some configurations, a separate resource manager device (such as /dev/tpmrm0) for coordinated access control.

Implementation-wise, the sysclasstpm is part of the kernel TPM subsystem. Drivers that manage TPM hardware register with the class, enabling a consistent file-system-based view of TPM devices across different hardware and firmware implementations. This design supports both physical TPMs connected over PCI/USB and software-based or virtual TPMs that present compatible interfaces to the kernel.

Usage and significance: TPMs provide hardware-backed cryptographic functions used for secure boot, measured boot, key storage, and attestation. System services and user-space tools (for example, tpm2-tools and tpm2-tss) interact with TPM devices through the standard character interfaces, while sysfs offers a transparent way to inspect device presence and capabilities.

See also: Trusted Platform Module, TPM 2.0, TPM 1.2, Linux kernel TPM subsystem, /sys/class/tpm, /dev/tpm, /dev/tpmrm, tpm-tools, tpm2-tools.