Guest environment for DF-2074 verification (HW-gated, source-only):

uname: DragonFly dfbsd 6.5-DEVELOPMENT DragonFly 6.5-DEVELOPMENT #0/#1
  #0 = Thu Jul  2 06:02:54 UTC 2026  (unpatched baseline, with-src snapshot)
  #1 = Sat Jul 25 11:53:22 UTC 2026   (combined-fix kernel, both DF-2073+DF-2074 applied)
cc:   cc 8.3 [DragonFly] Release/2019-02-22
kernel config: X86_64_GENERIC (options INVARIANTS)

Hardware gate (source-only confirmation):
  $ pciconf -l | grep -iE "ath|atheros|mlx|mylex"
  NO_HW_MATCH
  => No Mylex DAC960/acceleRAID RAID adapter present. mlxd child never attaches,
     so /dev/mlxd* does not exist and mlxd_strategy cannot be reached at runtime
     on this guest. Verification is by source trace only.

Source-tree confirmation (read-only sys/):
  sys/dev/raid/mlx/mlx_disk.c:156-190  mlxd_strategy
    - line 161: sc = (struct mlxd_softc *)bio->bio_driver_info  [READS uninit/stale]
    - line 173: sc->mlxd_drive->ms_state deref (wild if non-NULL stale)
    - line 179: devstat_start_transaction(&sc->mlxd_stats)
    - line 180: mlx_submit_bio(sc->mlxd_controller, bio)
  sys/dev/raid/mlx/mlx_disk.c:196       mlxd_intr   also reads bio_driver_info
  sys/dev/raid/mlx/mlx.c:683-693        mlx_submit_bio  does NOT set bio_driver_info
  sys/dev/raid/mlx/mlx.c:1713-1805      mlx_startio    line 1766 reads bio_driver_info
  sys/dev/raid/mlx/mlx.c:1810-1815      mlx_completeio line 1815 reads bio_driver_info
  sys/kern/vfs_bio.c:768-788            push_bio inits bio_prev/bio_buf/bio_offset/
                                        bio_done/bio_next ONLY -- NOT bio_driver_info
  sys/dev/raid/mlx/mlx_disk.c:260       mlxd_attach sets dsk->si_drv1 = sc
                                        (the CORRECT source, unused by strategy)
  Sibling reference (correct pattern):
  sys/dev/raid/amr/amr_disk.c:167-182   amrd_strategy: sc=dev->si_drv1 THEN
                                        bio->bio_driver_info=sc for downstream

Fix validation:
  fix.diff applied to /usr/src; combined (DF-2073+DF-2074) nativekernel build:
    rc=0, -Werror clean (no error/warning), kernel.stripped+kernel.debug produced
  Booted as kern.version #1 (Sat Jul 25 11:53:22 UTC 2026); guest healthy.
  Runtime before/after NOT possible (HW absent) => not_testable at runtime;
  build-validated + source-traced.