ampere iter2: HEVC EXT_SPS_ST_RPS / _LT_RPS dynamic-array submission (VDPU381)

Fixes the rkvdec_hevc_prepare_hw_st_rps out-of-bounds kernel OOPS that
blocked HEVC decode on ampere (RK3588) per
marfrit/libva-v4l2-request-fourier#3 and ampere-fourier iter1 close.

Mechanism (Phase 5 amendment to issue body):
The new EXT_SPS controls are registered as V4L2_CTRL_FLAG_DYNAMIC_ARRAY
in vdpu38x_hevc_ctrl_descs (rkvdec.c:279/284) with cfg.dims = { 65 }.
The v4l2-ctrl framework init-allocates 1 zeroed element (ctrls-core.c:2116).
When num_short_term_ref_pic_sets > 1, rkvdec_hevc_prepare_hw_st_rps
(rkvdec-hevc-common.c:393-405) iterates idx 0..N-1 and overruns the
1-element kernel allocation. Submitting an N-element dynamic-array
control via S_EXT_CTRLS extends the framework allocation.

Userspace fix:
  - VIDIOC_QUERY_EXT_CTRL probe at first HEVC CreateContext sets
    driver_data->has_ext_sps_rps (true on VDPU381/383, false on legacy
    RK3399 — control unregistered there, so fresnel iter38 5/5 + iter39
    sub-profile paths are byte-identical to pre-iter2).
  - When set, h265_set_controls appends EXT_SPS_ST_RPS + _LT_RPS as
    calloc'd zero arrays, sized by VAAPI's count fields and capped at
    H.265 §7.4.3.2 spec maxima (ST 64, LT 32). Min 1 (kernel rejects 0).
  - Free post-S_EXT_CTRLS.

Decode correctness scope:
VAAPI does NOT expose per-set st_ref_pic_set syntax elements
(delta_idx_minus1, delta_rps_sign, etc.) — confirmed in va_dec_hevc.h.
All-zero entries give empty inter-pred RPS per set, which is correct
for IDR-only streams and incorrect for streams with inter-pred RPS
dependence. iter2 acceptance: stop the OOPS. Decode-correctness for
inter-RPS content is a known follow-up requiring either bitstream-snoop
or SPS-passthrough via a new VAAPI extension.

Files:
  - include/hevc-ctrls.h: #ifndef-guarded fallback definitions for
    V4L2_CID_STATELESS_HEVC_EXT_SPS_{ST,LT}_RPS + structs (ampere host
    is on linux-api-headers 6.19-1; the new CIDs land in 7.0).
  - src/request.h: driver_data->has_ext_sps_rps (persists for driver
    lifetime; gated solely by HEVC code path so cross-codec leakage
    impossible).
  - src/context.c: probe at HEVC CreateContext via v4l2_query_ext_ctrl.
  - src/h265.c: controls[5] → controls[7]; #include <hevc-ctrls.h>
    (replaces <linux/v4l2-controls.h>) for forward UAPI compatibility.

Compile-tested on boltzmann (aarch64 native, gcc 15.2.1): clean .so,
0 new warnings. Fresnel cross-device safety: legacy RK3399 rkvdec_ctrl
table omits the CIDs; probe returns false; new code path never executes.

iter39 sub-profile work (commits 662f887 + 8746690) is preserved
in-tree; iter2 is a forward-compatible additive change.

Refs:
  marfrit/libva-v4l2-request-fourier#3
  ampere-fourier/iter1_close.md HEVC blocker
  ampere-fourier/iter2_phase0_findings.md

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/request.h

@@ -144,6 +144,20 @@ struct request_data {
 	 * Reset to false at DestroyContext.
 	 */
 	bool is_10bit;
+
+	/*
+	 * iter2 (ampere-fourier): rkvdec on this host exposes the
+	 * V4L2_CID_STATELESS_HEVC_EXT_SPS_ST_RPS dynamic-array control
+	 * (VDPU381/383 path). When true, h265_set_controls appends
+	 * EXT_SPS_ST_RPS + EXT_SPS_LT_RPS (zero-initialized arrays sized
+	 * by VAAPI's count fields, capped at H.265 spec maxima 64/32).
+	 * Required to prevent rkvdec_hevc_prepare_hw_st_rps out-of-bounds
+	 * kernel OOPS when num_short_term_ref_pic_sets > 1.
+	 * Probed at first HEVC CreateContext via VIDIOC_QUERY_EXT_CTRL.
+	 * Persists for driver lifetime (gated solely by HEVC-only code
+	 * path, so cross-codec leakage cannot occur).
+	 */
+	bool has_ext_sps_rps;
 };
 
 VAStatus VA_DRIVER_INIT_FUNC(VADriverContextP context);