News › linux
By The Linux Camp News, October 30, 2026
The generic framework enables hub integration, not complete NXP hardware support. Its documented design also keeps downstream ports in one shared address domain.
Core I3C hub support was reported merged for Linux 7.4 by Phoronix on October 30, 2026, following Alexandre Belloni's October 28 pull request. The change adds infrastructure for hubs that expand and bridge communication among I3C-connected devices. This is a development-tree milestone, not a final 7.4 release announcement: Belloni explicitly said hardware drivers were still being worked on. 1 3
The patch-series history explains how the generic framework separates logical device ownership from physical-controller operations. A downstream device's descriptor, the kernel record representing it, stays associated with its virtual controller. A permanent parent-facing descriptor handles operations performed by the physical parent controller. That arrangement replaces temporary descriptor reparenting and temporary changes to the hub's dynamic address in earlier revisions. These are the series' documented design details, rather than an independent inspection of the merged implementation. 4
The immediate beneficiaries are hub-driver and platform integrators. The wider proposal includes an NXP P3H2x4x multi-function parent driver, regulator support and a hub child driver, but the generic pieces were deliberately made independently applicable. The practical inference is that a 7.4 version label alone is not proof of working NXP hub support. Integrators should check hardware-driver availability separately, because the maintainer's later pull request describes only core support as ready. 2 4 3
Virtual controllers do not imply independent addressing. The series documents that downstream ports share the parent controller's dynamic-address domain, with no independent per-port dynamic address assignment, or DAA. Consequently, platform designs must not treat each virtual bus as a separate address namespace. 2
Driver authors should also review command scope. The series warns that a broadcast common command code, or CCC, issued on a virtual bus reaches the parent bus and devices behind other connected ports. Use directed CCCs for per-device operations: selecting a virtual bus does not itself confine a broadcast to that port. 2