EISA bus support (Extended Industry Standard Architecture)
Core support for EISA, a 32-bit expansion bus that competed with IBM's MCA in late-1980s and early-1990s servers and workstations before PCI displaced it around 1995. The code handles bus enumeration and PCI-to-EISA bridges so that EISA network cards, SCSI controllers, and similar add-in boards still work on legacy systems, including some PA-RISC machines that Linux continues to support.
recommendation
Worth keeping but flagging as legacy because the bus itself hasn't shipped in new hardware since the mid-1990s, yet the subsystem is still receiving genuine maintenance fixes as recently as April 2025 and is depended on by other in-tree code such as PA-RISC platform support and a handful of older SCSI drivers. Removing it would break those still-supported legacy configurations, so the right move is to document its obsolete status rather than deprecate the code.
repository signals
sources
- spinics.net
April 2025 patch traffic shows the subsystem still receives upstream fixes, here for string-size/build correctness in EISA code.
- spinics.net
April 2025 follow-up patch fixes an EISA build failure, indicating current maintenance rather than abandonment or removal.
- cateee.net
LKDDb shows CONFIG_EISA is still present in current kernel series and describes EISA as a legacy bus whose main use window was 1988-1995.
- cateee.net
LKDDb shows drivers/eisa also covers generic PCI-to-EISA bridge support, confirming this directory is active bus support code rather than dead documentation or tables.
- en.wikipedia.org
EISA is a historical expansion bus superseded by PCI, supporting the conclusion that new-hardware deployment is effectively gone.
codex reasoning notes (technical)
Not an early-exit case: local shell inspection showed real kernel bus-support code in drivers/eisa/*.c, including bus registration and initcalls. Local shell `git log` showed substantive touches in 2023-2025, and local grep showed current in-tree dependencies from legacy arches and drivers (for example parisc and EISA-dependent SCSI drivers), so this is still live compatibility infrastructure. Source acquisition: the two spinics URLs were obtained by web search for recent EISA patch subjects after lore-specific search/tooling was unavailable here; the cateee LKDDb URLs were obtained by web search; the Wikipedia URL is a canonical stable page recalled directly. No removal discussion was found in the gathered evidence; activity looks like low-volume maintenance for old but still-supported legacy systems. That supports `keep-annotate`: mark as legacy/obsolete hardware support, but do not deprecate/remove solely on market obsolescence.