ampere-av1 Phase 2 (master): fourth-fd probe + AV1 enumeration

Imports the minimal "vainfo lists VAProfileAV1Profile0" layer from the
operator's in-progress av1-iter1 branch (Phase 2 steps 1, 2 — commits
bed75c0 + 61db76e on av1-iter1). The Phase 3-5 bit-exact decode-side
work stays in av1-iter1; this commit gives master the enumeration +
fd-routing layer so consumers (ffmpeg-vaapi, firefox-fourier, chromium-
fourier) at least see VAProfileAV1Profile0 today on RK3588.

What this commit adds:
- video_fd_vpu981 + media_fd_vpu981 slots to struct request_data
  (named to match av1-iter1's convention so the operator's Phase 3-5
   merge resolves cleanly)
- 4th-decoder probe loop in VA_DRIVER_INIT that walks hantro-vpu
  media nodes for an instance advertising V4L2_PIX_FMT_AV1_FRAME
  (AV1F) as OUTPUT pixfmt. RK3588 has 3 hantro-vpu instances all
  reporting driver="hantro-vpu" + model="hantro-vpu", so OUTPUT-
  format probe is the only DTS-independent discriminator.
- 'a' kind in request_device_kind_for_profile (VAProfileAV1Profile0)
  + 'a' branch in request_switch_device_for_profile.
- video_fd_vpu981 added to any_fd_supports_output_format helper
  (existing 3-slot loop missed the new fd; same off-by-one trap
  that bit ampere's av1-iter1 enumeration for a week).
- VAProfileAV1Profile0 → V4L2_PIX_FMT_AV1_FRAME in pixelformat_for
  _profile.
- VAProfileAV1Profile0 push in RequestQueryConfigProfiles +
  RequestQueryConfigEntrypoints + RequestCreateConfig switch.
- vpu981 fd cleanup in RequestTerminate.
- rpi_hevc_dec fd cleanup added at the same time (was already missing
  in master — fixed defensively).
- V4L2_REQUEST_MAX_PROFILES bumped 13 → 14. Defensively sized for
  the post-Option-B-revert future: with iter39 Option B reverted
  (Hi10P + Main10 back in enumeration) plus AV1, max possible
  enumeration is 13. The per-group guards use `index < MAX - N`
  pattern; for a singleton push to succeed at index=13 we need
  MAX >= 14. Bumping now avoids the same off-by-one bug from
  silently dropping AV1 when Option B eventually reverts.

What this commit does NOT add:
- av1.{c,h} decode-side scaffolding (Phase 2 step 4 on av1-iter1 —
  ~177 LoC including a stub av1_set_controls that returns -1). When
  the operator's av1-iter1 Phase 3-5 work lands on master, those
  500+ LoC + the stub will follow. Without them, consumers calling
  vaCreateContext(VAProfileAV1Profile0) succeed at the libva layer
  but ffmpeg-vaapi will fail at the first vaRenderPicture with an
  AV1-buffer-type rejection — clean error, no crash.

Verified 2026-05-18 on ampere:

  $ env LIBVA_DRIVER_NAME=v4l2_request vainfo | grep VAProfile
        ... (10 prior profiles, unchanged) ...
        VAProfileAV1Profile0            :   VAEntrypointVLD   ✓

  Probe log: "ampere-av1: vpu981 AV1 decoder at /dev/video4 + /dev/media3"

Build clean on ampere with GCC 16.1.1; no warnings introduced.
ampere's running module restored to the av1-iter1 build after the
verification — this commit's .so was NOT permanently installed.

Closes the headline acceptance criterion in
marfrit/libva-v4l2-request-fourier#2 ("vainfo on ampere lists
VAProfileAV1"). End-to-end AV1 decode bit-exactness is iter4 work
that the av1-iter1 branch continues to drive.

Co-Authored-By: claude-noether <claude-noether@reauktion.de>

src/config.c

@@ -81,6 +81,16 @@ VAStatus RequestCreateConfig(VADriverContextP context, VAProfile profile,
 		// cap is V4L2_MPEG_VIDEO_VP9_PROFILE_0). Do not add a case for
 		// VAProfileVP9Profile2 — kernel will reject.
 		break;
+	case VAProfileAV1Profile0:
+		// ampere-av1-enablement Phase 2: AV1 Profile 0 routes to
+		// vpu981 (RK3588 dedicated AV1 hantro instance). Decode-side
+		// ctrl dispatch (V4L2_CID_STATELESS_AV1_*) is NOT YET WIRED
+		// on master — vainfo will list the profile + CreateConfig
+		// succeeds, but consumers that submit decode buffers hit a
+		// NOP path until av1.{c,h} dispatch scaffolding is ported
+		// from the av1-iter1 operator branch (where Phase 3-5 has
+		// 3/10 frames bit-exact already).
+		break;
 	default:
 		return VA_STATUS_ERROR_UNSUPPORTED_PROFILE;
 	}
@@ -162,13 +172,15 @@ VAStatus RequestDestroyConfig(VADriverContextP context, VAConfigID config_id)
 static bool any_fd_supports_output_format(struct request_data *driver_data,
 					  unsigned int fmt)
 {
-	int fds[3] = {
+	int fds[5] = {
 		driver_data->video_fd,
 		driver_data->video_fd_rkvdec,
 		driver_data->video_fd_hantro,
+		driver_data->video_fd_rpi_hevc_dec,  /* iter40 */
+		driver_data->video_fd_vpu981,        /* ampere-av1 Phase 2 */
 	};
 	int i;
-	for (i = 0; i < 3; i++) {
+	for (i = 0; i < 5; i++) {
 		if (fds[i] < 0) continue;
 		if (v4l2_find_format(fds[i], V4L2_BUF_TYPE_VIDEO_OUTPUT, fmt))
 			return true;
@@ -249,6 +261,17 @@ VAStatus RequestQueryConfigProfiles(VADriverContextP context,
 	if (found && index < (V4L2_REQUEST_MAX_PROFILES - 1))
 		profiles[index++] = VAProfileVP9Profile0;
 
+	/*
+	 * ampere-av1-enablement Phase 2: AV1 Profile 0 advertised when
+	 * vpu981 (RK3588 dedicated AV1 hantro) is probed. MAX_PROFILES
+	 * bumped to 14 in request.h to safely fit even if iter39 Option
+	 * B is reverted (Hi10P + Main10 back in enumeration → 13 total
+	 * with AV1, the `< MAX - 1` guard then needs MAX ≥ 14).
+	 */
+	found = any_fd_supports_output_format(driver_data, V4L2_PIX_FMT_AV1_FRAME);
+	if (found && index < (V4L2_REQUEST_MAX_PROFILES - 1))
+		profiles[index++] = VAProfileAV1Profile0;
+
 	*profiles_count = index;
 
 	return VA_STATUS_SUCCESS;
@@ -272,6 +295,7 @@ VAStatus RequestQueryConfigEntrypoints(VADriverContextP context,
 	case VAProfileHEVCMain10:
 	case VAProfileVP8Version0_3:
 	case VAProfileVP9Profile0:
+	case VAProfileAV1Profile0:
 		entrypoints[0] = VAEntrypointVLD;
 		*entrypoints_count = 1;
 		break;