IDT/Renesas Tsi721 PCIe-to-Serial-RapidIO bridge
Support for the Tsi721, a PCI Express to Serial RapidIO bridge chip originally from IDT and now sold by Renesas, along with the generic RapidIO message-port character-device interface that lets userspace talk to RapidIO fabrics. RapidIO is a high-speed interconnect used in niche embedded markets like defense, aerospace, video and imaging gear, and wireless base stations.
recommendation
Worth keeping but documenting as niche, because Renesas still actively sells the Tsi721 in 2025 for specialised embedded markets and the code is still receiving real maintenance, including a 2024 tasklet-to-workqueue conversion in the DMA path and ongoing bug fixes in the mport character-device layer. There is no replacement driver covering the same PCIe-to-SRIO bridging role, so removing it would leave existing defense, aerospace, and wireless deployments stranded even though overall Linux deployment numbers are small.
repository signals
sources
- lore.kernel.org
`tsi721_dma.c` still received non-treewide maintenance in 2024 (`rapidio/tsi721: Convert from tasklet to BH workqueue`).
- lore.kernel.org
`rio_mport_cdev.c` still received real bug-fix traffic in 2026 (`fix sequential UAF in dma_req_free()`), indicating ongoing exposure/testing rather than abandonment.
- renesas.com
Vendor product page lists Tsi721 as an active RapidIO bridge product, supporting the conclusion that hardware was still sold new in 2025.
- renesas.com
Renesas still markets PCIe-to-Serial-RapidIO bridges for defense, aerospace, video, imaging, and wireless markets, indicating a niche but extant deployment base.
codex reasoning notes (technical)
Local shell inspection (`rg`/`sed`) showed this directory is real driver code centered on `tsi721*.c` plus generic RapidIO mport cdev support. `lore_file_timeline` on the three `.c` files showed continuing upstream fixes, especially heavy `rio_mport_cdev.c` activity and a 2024 `tsi721_dma.c` maintenance patch; that argues against deprecation/removal and there was no removal signal in those timeline results. Web search found Renesas canonical product pages showing Tsi721 still marked active/orderable, so hardware was still sold new in 2025, but the marketed uses are narrow embedded/industrial/defense/wireless niches, so present-day deployments are low. No clear upstream replacement driver covers the same PCIe-to-SRIO bridge use case, so keep the code but annotate it as niche/legacy rather than deprecating it.