USB Class Drivers (CDC ACM, USB Printer, CDC WDM, USBTMC)
Four standard USB device-class drivers: CDC ACM for modems and serial-over-USB adapters (including AT channels on cellular modules), usblp for USB printers, cdc-wdm for management channels on mobile broadband devices, and usbtmc for USB Test and Measurement Class instruments such as oscilloscopes and signal generators.
recommendation
It should stay because all four drivers cover USB device classes that current hardware still uses: Brother and others still ship USB printers, cellular modems from Quectel and peers rely on CDC ACM and CDC WDM, and Keysight test gear continues to expose USBTMC. Upstream activity is healthy, with new device quirks landing as recently as 2026, and there is no successor or removal effort in sight.
repository signals
sources
- git.kernel.org
Recent upstream maintenance continued in 2026 with commit `cdc-acm: new quirk for EPSON HMD` on 2026-03-18, indicating the directory is actively maintained rather than abandoned.
- cateee.net
LKDDb shows CONFIG_USB_ACM remains present through current kernel series and covers USB CDC ACM modem/serial devices in drivers/usb/class/cdc-acm.c.
- cateee.net
LKDDb shows CONFIG_USB_WDM remains present in current kernel series, supporting continued kernel exposure for CDC WDM management devices.
- brother-usa.com
A current Brother printer product page lists Hi-Speed USB 2.0 connectivity, showing USB printer-class hardware is still sold new.
- keysight.com
A 2025 Keysight programmer's manual explicitly documents USBTMC support, showing current test-and-measurement instruments still use the USB Test & Measurement Class.
- python.quectel.com
A 2025 Quectel USB application guide describes CDC-based USB AT/control interfaces on current cellular modules, supporting ongoing relevance for CDC ACM-class usage.
codex reasoning notes (technical)
Local shell inspection of Kconfig/Makefile showed this directory is a real driver collection with four modules: cdc-acm, usblp, cdc-wdm, and usbtmc. Local `git log` (run via shell with `-c safe.directory=...`) showed many substantive 2025-2026 fixes/quirks across all four drivers and no removal/deprecation-themed hits in a 2024+ grep, so there is active upstream attention and no visible removal push. The kernel.org commit URL was added by canonical recall from the locally retrieved commit hash; LKDDb, Brother, Keysight, and Quectel URLs were obtained via web search. Because the directory covers several still-current USB device classes with ongoing fixes and no single successor driver, the right action is keep, not deprecate or remove.