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DF-1150 fix compile-validation (radeon ci_dpm.c, sys/dev/drm/radeon)
Guest: DragonFly 6.5-DEVELOPMENT #0, cc 8.3, with-src (unpatched baseline)
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[1] APPLY fix.diff (6 clamp insertions expected):
    cd /usr/src && patch -p1 --forward < /root/df1150.diff
      Hunk #1 succeeded at 3511 ; Hunk #2 at 3525 ; Hunk #3 at 3538 (done)
    grep -c 'i < MAX_REGULAR_DPM_NUMBER' ci_dpm.c  ->  6

[2] INCREMENTAL MODULE BUILD (full radeon.ko, generates forwarder dir):
    cd /usr/src/sys/dev/drm/radeon && make
      -> radeon.ko produced (2029192 bytes), ci_dpm.o compiled & linked,
         MODULE_MAKE_RC=0, NO error:/warning: under -Werror
         (final link line includes ci_dpm.o)

[3] RESULT: fix.diff APPLIES + COMPILES clean (radeon module, -Werror).

[4] REVERT (source returned to unpatched baseline):
    cd /usr/src && patch -p1 -R < /root/df1150.diff  -> done
    grep -c 'i < MAX_REGULAR_DPM_NUMBER' ci_dpm.c  ->  1  (the pre-existing reset loop at ci_dpm.c:3415, unchanged) -- revert clean

RUNTIME: not exercised -- radeon not in GENERIC, no AMD GPU on guest (latent).