Serio bus and PS/2 host controllers (i8042 and friends)
The serio bus is the kernel's framework for PS/2-style serial input controllers: the venerable i8042 keyboard/mouse controller found on nearly every x86 PC, a few platform adapters, and the synthetic PS/2 devices that Hyper-V and QEMU present to virtual machines. It carries keystrokes and mouse motion from the chipset up to the input layer.
recommendation
It should stay in the kernel because the serio bus is still the standard path for PS/2 keyboards and mice on x86 systems, and it also carries the synthetic keyboard and mouse devices that Hyper-V and QEMU expose to virtual machines. Upstream activity is steady (around 130 commits in the last five years), and both real hardware and virtualization platforms continue to ship PS/2-class input interfaces in 2025.
repository signals
sources
- git.kernel.org
The directory continues to receive upstream changes in current kernels, which is inconsistent with an obsolescent or removal-ready subsystem.
- git.kernel.org
Kconfig describes core Serial I/O support, keeps SERIO and SERIO_I8042 enabled-by-default options, and shows the directory still covers mainstream PS/2 plus active platform/VM guest cases.
- docs.kernel.org
Hyper-V still exposes synthetic keyboard and mouse devices to Linux guests, so this directory serves active virtualization deployments, not only legacy bare-metal hardware.
- lists.gnu.org
QEMU maintains a documented I8042/PS/2 device interface, indicating continued relevance for virtual machine input paths that Linux serio/i8042 supports.
codex reasoning notes (technical)
Local shell inspection of Makefile/Kconfig shows this is a live subsystem directory containing the serio core plus many host-controller drivers, not a single dead chipset. No removal/deprecation signal was found in local history probes; static metadata already shows 130 substantive commits in 5 years with a 2026-02-23 touch. Source acquisition: kernel.org log URL and Kconfig tree URL are canonical-recall stable pages corresponding to the inspected path; Hyper-V VMBus page was obtained via web search (turn1search3); QEMU I8042 interface mail was obtained via web search (turn0search2). Recommendation is keep because current upstream activity is strong and deployments remain meaningful on x86 systems and VM guests.