PCIe Non-Transparent Bridge (NTB) core and vendor backends
PCIe Non-Transparent Bridges let two or more independent computers share a PCI Express fabric while keeping their memory spaces isolated, exposing controlled doorbells and memory windows so the hosts can exchange data. They are used in specialized multi-host server, storage, and embedded designs, with hardware from Intel, AMD, IDT, and Microchip's Switchtec PCIe switches.
recommendation
It should stay because this is the generic framework that all the vendor-specific NTB drivers (Intel, AMD, IDT, Microchip Switchtec) plug into, and there is no in-tree replacement. Although deployments are niche rather than mass-market, the code is actively maintained — core.c received new feature work in early 2026 (driver_override support) — and Microchip still sells current Gen 5 and Gen 6 PCIe switches advertising NTB capability, so the subsystem remains relevant for specialized multi-host systems.
repository signals
sources
- lore.kernel.org
`drivers/ntb/core.c` saw upstream feature work in January 2026 ('NTB: core: Add driver_override support for NTB devices'), so the subsystem is still maintained rather than abandoned.
- docs.kernel.org
Kernel documentation describes NTB as a current PCIe bridge class and `ntb` as the core framework used by hardware-specific NTB drivers and clients, confirming this directory is the active generic core for the subsystem.
- microchip.com
Microchip's current Switchtec PCIe switch portfolio page lists Gen 5 and Gen 6 products and explicitly advertises up to 48 Non-Transparent Bridges (NTBs), showing NTB-capable hardware was still sold new in and after 2025.
codex reasoning notes (technical)
`drivers/ntb` is the generic NTB core/framework, with vendor backends under `drivers/ntb/hw/` (Intel, AMD, IDT, Microchip Switchtec). Recent lore activity on `core.c` from `lore_file_timeline` shows live upstream development in 2026, which argues strongly against deprecation/removal. Deployment is niche rather than mass-market, so I marked it `low`, but current Microchip Switchtec products indicate NTB remains relevant for specialized server/storage/embedded multi-host designs. No natural in-tree replacement exists for the NTB core API. Source acquisition: lore URL via `lore_file_timeline`; docs.kernel.org URL identified from local `Documentation/driver-api/ntb.rst` and confirmed via `web.search_query`; Microchip product URL obtained via `web.search_query`.