drivers/net/caif · remove

CAIF network layer for ST-Ericsson cellular modems

CAIF (Communication CPU to Application CPU Interface) is a multiplexing protocol that ST-Ericsson cellular modems used to talk to their host application processor over serial links and, later, virtio. It was used in phones and embedded devices built around ST-Ericsson modem chips in the late 2000s and early 2010s.

remove conf=0.89 last_sold=2013 deploy=low replacement=none subsystem=net category=networking-other

89%

recommendation

Already on the path to removal: a patch series titled "caif: remove CAIF NETWORK LAYER" is in flight on the netdev mailing list, and the joint venture behind the hardware (ST-Ericsson) was dissolved in August 2013, so no new devices have shipped in over a decade. A small virtio transport remains for niche virtualization or testing use, but with the upstream networking maintainers actively tearing the stack out, the whole subtree is expected to disappear from mainline soon.

repository signals

4 files

1,234 source lines

25 commits, 5y

+40 / −1,523 lines added / removed, 5y

17 authors, 5y

monthly commits · 2021-04-21 → 2026-04-21 · 25 total · active in 14/61 months

sources

lore.kernel.org
Netdev carried a 2026-04-16 patch titled "caif: remove CAIF NETWORK LAYER", showing active upstream removal work touching this driver area.
docs.kernel.org
Kernel documentation says CAIF is a mux protocol used by ST-Ericsson cellular modems and describes UART/loopback Linux transports, tying the stack to legacy ST-Ericsson modem hardware.
docs.kernel.org
Kernel usage documentation explicitly frames CAIF setup around an "STE modem", reinforcing that deployments are tied to old ST-Ericsson phone-modem integrations.
en.wikipedia.org
ST-Ericsson was dissolved in August 2013, making fresh 2025 sales of native ST-Ericsson CAIF modem hardware unlikely.
cateee.net
LKDDb shows a CAIF virtio transport still exists upstream, suggesting a residual virtualization/testing niche even as physical hardware is obsolete.

codex reasoning notes (technical)

Recommend remove: lore_file_timeline on drivers/net/caif/caif_serial.c and caif_virtio.c surfaced the netdev removal patch URL, which outweighs recent maintenance traffic. Kernel-doc URLs were obtained via web search and show CAIF is specific to ST-Ericsson/STE modems. The ST-Ericsson URL was obtained via web search and supports the 2013 obsolescence cutoff. LKDDb URL was obtained via web search and supports only a small remaining virtio niche, so deployments are low rather than none.