Qualcomm MHI Bus Endpoint Support for PCIe Modems
The endpoint side of Qualcomm's Modem-Host Interface (MHI) protocol, used by PCIe-attached cellular modems such as the Snapdragon X55 (SDX55) and successors when the modem itself is the PCIe device talking to a Linux host. It underpins 4G/5G connectivity in laptops, industrial gateways, routers, and embedded WWAN modules, including current Quectel RM520N-class 5G cards still shipping in 2025.
recommendation
It should stay because the code is actively maintained, with commits landing through late 2025, and the hardware it supports is firmly current: Qualcomm-based 5G modems using MHI over PCIe are still being sold and deployed in routers, gateways, signage, and laptops. There is no deprecation signal, and removing it would break a mainstream class of cellular connectivity hardware.
repository signals
sources
- git.kernel.org
Kconfig describes this as the MHI bus endpoint implementation and explicitly cites endpoint devices such as the SDX55 modem connected to a host over PCIe.
- git.kernel.org
The directory has ongoing upstream commit history rather than abandonment, consistent with continued maintenance into late 2025.
- kernel.org
Kernel documentation describes MHI as a Qualcomm-developed protocol used primarily with PCIe-based modem devices.
- quectel.com
Current Quectel RM520N 5G modules are still marketed with PCIe and Linux driver support for industrial, gateway, laptop, and signage deployments, indicating the underlying MHI-style modem endpoint use case remains current.
codex reasoning notes (technical)
Real driver, not an early-exit case: local `rg` on the directory found MHI endpoint bus code and Kconfig text naming SDX55 modem endpoints. Upstream activity is strong: local `git -c safe.directory=... log -- drivers/bus/mhi/ep` showed many non-removal commits through late 2025; the kernel.org log URL is cited as the canonical stable page for that history. No removal signal was found in the accessible evidence, so active maintenance outweighs any deprecation concern. Deployment is not broad consumer-PC scale but still material in embedded/industrial WWAN, routers, gateways, and similar PCIe modem products; that supports `medium` deployments and `keep`. URL acquisition: kernel.org Kconfig/log URLs by canonical recall, MHI docs and Quectel product page via web search.