linux-drivers/
drivers/usb/serial

USB-to-serial bridges and modem control ports

A broad collection of drivers for USB devices that present themselves to the operating system as classic serial (RS-232 / tty) ports. This covers FTDI, Prolific, CP210x and similar USB-to-serial cable adapters used for industrial gear and embedded development, plus the AT command and diagnostic ports exposed by cellular modems from vendors like Sierra Wireless, Quectel, and Telit.

keep conf=0.94 deploy=high replacement=none subsystem=usb category=bus-usb
94%

recommendation

It should stay in the kernel because this is an actively maintained subsystem with new device IDs and fixes landing throughout 2025 across drivers like ftdi_sio, option, f81232, and io_edgeport. The hardware it supports is still sold new today, ranging from FTDI and USBGear RS-232 adapters to current Sierra Wireless 5G modems and OWON oscilloscopes whose control ports rely on these drivers.

repository signals

83 files
58,754 source lines
315 commits, 5y
+2,749 / −2,172 lines added / removed, 5y
132 authors, 5y
monthly commits · 2021-04-21 → 2026-04-21 · 315 total · active in 60/61 months
2021 2022 2023 2024 2025 2026 2021-04: 2 commits · +14 −0 2021-05: 16 commits · +147 −165 2021-06: 5 commits · +242 −88 2021-07: 15 commits · +72 −107 2021-08: 11 commits · +136 −200 2021-09: 13 commits · +99 −67 2021-10: 6 commits · +71 −145 2021-11: 4 commits · +10 −2 2021-12: 1 commit · +8 −0 2022-01: 2 commits · +3 −0 2022-02: 8 commits · +35 −95 2022-03: 3 commits · +5 −1 2022-04: 9 commits · +25 −4 2022-05: 4 commits · +9 −6 2022-06: 9 commits · +45 −25 2022-07: 4 commits · +20 −7 2022-08: 7 commits · +134 −67 2022-09: 21 commits · +312 −331 2022-10: 1 commit · +5 −0 2022-11: 10 commits · +46 −18 2022-12: 5 commits · +14 −3 2023-01: 6 commits · +11 −4 2023-02: 2 commits · +5 −0 2023-03: 5 commits · +11 −17 2023-04: 1 commit · +6 −0 2023-05: 1 commit · +16 −0 2023-06: 5 commits · +154 −72 2023-07: 5 commits · +133 −34 2023-08: 4 commits · +9 −4 2023-09: 1 commit · +1 −0 2023-10: 3 commits · +8 −2 2023-11: 3 commits · +6 −1 2023-12: 3 commits · +9 −6 2024-01: 5 commits · +12 −2 2024-02: 6 commits · +11 −3 2024-03: 3 commits · +8 −0 2024-04: 4 commits · +34 −0 2024-05: 5 commits · +11 −84 2024-06: 7 commits · +86 −3 2024-07: 4 commits · +11 −3 2024-08: 1 commit · +5 −0 2024-09: 3 commits · +44 −1 2024-10: 5 commits · +24 −12 2024-11: 8 commits · +29 −8 2024-12: 3 commits · +36 −1 2025-01: 5 commits · +16 −10 2025-02: 4 commits · +29 −38 2025-03: 5 commits · +66 −16 2025-04: 3 commits · +10 −5 2025-05: 3 commits · +7 −4 2025-06: 4 commits · +21 −16 2025-07: 4 commits · +13 −3 2025-08: 3 commits · +18 −1 2025-09: 1 commit · +6 −0 2025-10: 12 commits · +125 −175 2025-11: 12 commits · +102 −144 2025-12: 3 commits · +51 −30 2026-01: 1 commit · +6 −0 2026-02: 4 commits · +143 −142 2026-03: 2 commits · +4 −0 2026-04: 0 commits · +0 −0

sources

  1. opennet.ru

    Stable changelog entries for April 2025 show ongoing upstream additions in this directory, including new support in `ftdi_sio`, `option`, and `usb-serial-simple`, indicating active maintenance rather than retirement.

  2. usbgear.com

    USBGear still sells a Linux-compatible USB-to-RS232 adapter, showing the basic USB-serial use case remains current in 2025.

  3. ftdi-chip.com

    FTDI-branded USB-to-serial/RS-232 converter products are still listed as in stock, showing new USB-serial bridge hardware remains commercially available.

  4. sierrawireless.com

    The Sierra Wireless EM9291 5G module is a current product class whose AT/diagnostic ports map to the `option` USB-serial driver family in this directory.

  5. owonna.com

    OWON HDS200 test equipment is a current product line; upstream added support for this class in `usb-serial-simple` in 2025, evidencing present-day deployments beyond legacy adapters.

codex reasoning notes (technical)

Real driver directory, not an early-exit case. Upstream activity was checked first via local shell (`git -c safe.directory=... log -- drivers/usb/serial`), which showed many 2025-2026 commits adding IDs and fixes across `option`, `ftdi_sio`, `f81232`, `io_edgeport`, etc. Because `lore-http` MCP was unavailable and `lei` was not installed, deployment/removal evidence used web search. `https://www.opennet.ru/kernel/6.12.26.html` was obtained by web search/open and shows fresh upstream USB-serial additions; searches for removal discussion on lore terms returned no relevant hit. Current-hardware evidence came from web search/open on USBGear, FTDI, Sierra Wireless, and OWON product pages. This directory is an actively maintained subsystem covering still-sold adapters, industrial/test gear, and cellular modem control ports, so removal/deprecation is not indicated.