From: John Groves <[email protected]> This series adds famfs mode support to daxctl, alongside the existing devdax and system-ram modes. A daxdev is in famfs mode when it is bound to fsdev_dax.ko (drivers/dax/fsdev.c). famfs is a shared, memory-mappable filesystem for disaggregated and CXL memory; see https://famfs.org for more information.
Patch 1 adds the library plumbing: mode detection helpers, an enable function, and the device.c reconfigure-device wiring. Patch 2 adds a test that exercises mode transitions on the nfit_test emulated backend. This series depends on the fsdev_dax kernel driver (which provides famfs mode) and on the famfs kernel patch series. Changes since V5 (addressing Alison's review): Patch 1 (daxctl: Add support for famfs mode): - Commit message: add an intro paragraph describing what famfs is, with a link to https://famfs.org. - Documentation: document famfs mode in Documentation/daxctl/daxctl-reconfigure-device.txt (DESCRIPTION, the -m/--mode option list, and a reconfigure example). - Rename the local 'enum dev_mode' to 'enum reconfig_mode' (RECONFIG_MODE_*) so it no longer shares member names with enum daxctl_dev_mode. - Add daxctl_dev_get_mode(), which reports a device's current mode; the three reconfig_mode_*() functions and json.c now switch on it instead of repeating an if-else mode chain. enum daxctl_dev_mode moves to the public header and gains a DAXCTL_DEV_MODE_UNKNOWN sentinel; daxctl_dev_get_mode() is exported. - Collapse disable_devdax_device() and disable_famfs_device() into a single disable_mode_device() (the caller has already matched the mode). - Add daxctl_dev_is_system_ram_mode() as the preferred name for the consistency with daxctl_dev_is_{famfs,devdax}_mode(); daxctl_dev_is_system_ram_capable() becomes a compatibility wrapper so the existing ABI is preserved. - Move the "returns false for a disabled device" note onto the shared daxctl_dev_bound_to_module() helper and drop the redundant per-predicate comments. - Fix daxctl_dev_enable() to range-check mode before indexing dax_modules[]; the lookup previously ran before the bounds check. - Remove the stray double space in the --mode=famfs parse branch. - Drop the Reviewed-by: Dave Jiang tag, given the amount of rework since V5. Patch 2 (test): - Replace the V5 device-scanning test with test/daxctl-famfs-nfit.sh, which builds its own dax device from the emulated ACPI.NFIT bus (nfit_test) so it runs in the ndctl unit-test model. Real DRAM backing means kmem onlining works and the full devdax/famfs/system-ram matrix runs end-to-end, including the system-ram -> famfs rejection. Follows the existing test style (set -x logging, err/cleanup traps, check_dmesg, fixture teardown). Based on a rewrite from Alison Schofield. - Per Alison's "pick a lane to start" feedback, only the nfit_test backend is upstreamed here; a cxl_test-backed variant is held for a later revision. John Groves (2): daxctl: Add support for famfs mode Add nfit_test famfs mode-transition test .../daxctl/daxctl-reconfigure-device.txt | 22 +- daxctl/device.c | 113 ++++++--- daxctl/json.c | 18 +- daxctl/lib/libdaxctl-private.h | 9 +- daxctl/lib/libdaxctl.c | 73 +++++- daxctl/lib/libdaxctl.sym | 9 + daxctl/libdaxctl.h | 14 ++ test/daxctl-famfs-nfit.sh | 215 ++++++++++++++++++ test/meson.build | 2 + 9 files changed, 432 insertions(+), 43 deletions(-) create mode 100755 test/daxctl-famfs-nfit.sh -- 2.53.0
