Nokia HSI Modem Clients (N900/N9/N950 SSI, McSAAB, CMT Speech)
Client modules for the High-Speed Synchronous Serial Interface used between the application processor and the cellular modem in Nokia's last Linux-based smartphones — the N900 (2009), N9, and N950 — implementing the McSAAB SSI transport, the CMT speech audio path, and a character-device interface to the modem. The hardware has not been sold new since around 2011.
recommendation
Worth keeping but flagging as legacy because the only known users are Nokia's last Linux-based handsets (N900, N9, N950) from 2009-2011, yet the code is still receiving real maintenance — including a use-after-free fix to the SSI protocol code in February 2025. There is no removal effort underway, so it should remain available for the small community still running these phones, but a note clarifying its purely legacy scope would help future maintainers.
repository signals
sources
- cateee.net
CONFIG_NOKIA_MODEM covers Nokia modem support in this directory and names Nokia N900/N9/N950 device-tree compatibles, tying the directory to legacy Nokia handset modem hardware.
- cateee.net
CONFIG_SSI_PROTOCOL is still present through current kernel series and describes the McSAAB SSI protocol used by these clients.
- cateee.net
CONFIG_CMT_SPEECH is still present and explicitly says it is the CMT speech protocol used by Nokia modems.
- git.kernel.org
The directory received a substantive fix on 2025-02-25 for a use-after-free in ssi_protocol, showing ongoing upstream bug-fix attention rather than abandonment.
- en.wikipedia.org
The Nokia N900 launched in 2009, supporting the conclusion that the user-visible hardware class is long out of new-product circulation.
codex reasoning notes (technical)
Directory inspection via shell (`rg`, file reads) shows real HSI client drivers: `nokia-modem.c`, `ssi_protocol.c`, `cmt_speech.c`, and `hsi_char.c`, with Nokia modem aliases and SSI/Phonet plumbing. Lore MCP was unavailable and `lei` was not installed, so upstream activity was checked from local git history via shell; that showed a real 2025 security/bug fix in `ssi_protocol` and several recent treewide updates, with no evidence gathered of an active removal series. Deployment looks legacy-only: LKDDb ties the code to Nokia N900/N9/N950-era modem hardware, and the N900 source dates the product family to 2009. That argues against removal today, but the hardware is obsolete enough that the directory should be annotated as legacy rather than treated as strategic for new deployments.