request: route VP9/AV1/H.264 to daedalus_v4l2 on Pi 5 mixed deploy

LIBVA-1 — when both rpi-hevc-dec and daedalus_v4l2 are loaded, finish
the per-codec dispatch so HEVC goes to rpi-hevc-dec (existing 'p'
override) and VP9 / AV1 / H.264 go to the daedalus daemon ('d').

Before this change the multi-device-probe accepted only ONE driver
plus a fixed alt slot (rkvdec↔hantro-vpu); on a Pi 5 with both decoders
the find_codec_device() walk preferred rpi-hevc-dec by known_decoder_
drivers[] order and never opened daedalus_v4l2, so VP9/AV1/H.264 frames
hit rpi-hevc-dec's S_FMT and failed.

Changes:

  - request.c multi-device-probe: when primary = rpi-hevc-dec, alt =
    daedalus_v4l2 (when HAVE_DAEDALUS_V4L2 is on); symmetric handling
    in the daedalus_v4l2 primary branch so alt = rpi-hevc-dec.  This
    preserves the iter40 fallback (no daedalus → alt = NULL) when the
    build option is off.

  - request.c alt-driver opening block: generalized from the iter38
    rkvdec/hantro pair to also dispatch into video_fd_rpi_hevc_dec and
    video_fd_daedalus slots.  Defensive close on unknown alt-driver
    name (shouldn't happen — primary_driver branches gate the choices —
    but keeps the slot tally clean if a future driver name is added
    above without wiring up the dispatch here).

  - request_switch_device_for_profile: added 'd' kind handler +
    profile override block.  When daedalus is open, VP9 / AV1 / H.264*
    route to it.  HEVC stays on rpi-hevc-dec via the existing 'p'
    override.  AV1 'a' kind (RK3588 vpu981) wins ONLY if vpu981 was
    probed, so the override only fires on hosts where vpu981 stayed
    -1 (i.e. Pi 5).

  - RequestTerminate: close the daedalus_v4l2 fd pair on teardown
    (was leaking — caught while reviewing the alt-driver expansion).

Build: meson + ninja clean on boltzmann (only pre-existing GStreamer
H265 parser noise).  Behaviour on RK3399/3588 boxes unchanged — the
new branches are gated by HAVE_DAEDALUS_V4L2 *and* video_fd_daedalus
≥ 0, both of which stay false in those deployments.

Companion to daedalus-v4l2 481279c (Phase 8.13 systemd unit) and
marfrit-packages noether/daedalus-v4l2-kernel-6.18-compat branch.

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

meson_options.txt

@@ -4,3 +4,14 @@ option(
     value : '',
     description: 'Path to sanitized Linux Kernel headers'
 )
+
+option(
+    'daedalus_v4l2',
+    type : 'boolean',
+    value : true,
+    description: 'Enable probe + dispatch for the out-of-tree daedalus_v4l2 ' +
+                 'stateless decoder shim (Pi 5 / CM5 daemon-backed VP9/AV1/H264). ' +
+                 'Default true; disable on platforms where the daedalus_v4l2 ' +
+                 'kernel module will never be present to slim the probe array.'
+)
+

src/codec.c

@@ -46,6 +46,20 @@ unsigned int pixelformat_for_profile(VAProfile profile)
 		return V4L2_PIX_FMT_VP8_FRAME;
 	case VAProfileVP9Profile0:
 		return V4L2_PIX_FMT_VP9_FRAME;
+	case VAProfileAV1Profile0:
+		/*
+		 * ampere-av1-enablement Phase 2: AV1 Profile 0 routes to
+		 * vpu981 (RK3588's dedicated AV1 hantro). Per-codec ctrl
+		 * dispatch (V4L2_CID_STATELESS_AV1_*) is NOT YET WIRED on
+		 * master — vainfo lists the profile + RequestCreateConfig
+		 * succeeds, but consumers that submit decode buffers hit
+		 * a NOP path until the per-codec dispatch lands. The
+		 * av1-iter1 operator branch has Phase 3 bit-exact bring-up
+		 * underway; this commit gives master the bare enumeration +
+		 * fd-routing layer so consumers like ffmpeg-vaapi at least
+		 * see VAProfileAV1Profile0 today.
+		 */
+		return V4L2_PIX_FMT_AV1_FRAME;
 	default:
 		return 0;
 	}

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;

src/meson.build

@@ -22,6 +22,9 @@
 
 autoconf_data = configuration_data()
 autoconf_data.set('VA_DRIVER_INIT_FUNC', va_driver_init_func)
+if get_option('daedalus_v4l2')
+	autoconf_data.set('HAVE_DAEDALUS_V4L2', 1)
+endif
 
 autoconf = configure_file(
 	output: 'autoconfig.h',

src/request.c

@@ -94,6 +94,9 @@ static const char * const known_decoder_drivers[] = {
 	"rkvdec",
 	"hantro-vpu",
 	"rpi-hevc-dec",  /* iter40: Pi 5 / CM5 stateless HEVC */
+#ifdef HAVE_DAEDALUS_V4L2
+	"daedalus_v4l2", /* phase 8.10: Pi 5 daemon-backed VP9/AV1/H264 */
+#endif
 	"cedrus",
 	"sun4i_csi",
 	NULL
@@ -409,6 +412,16 @@ char request_device_kind_for_profile(VAProfile profile)
 	case VAProfileMPEG2Main:
 	case VAProfileVP8Version0_3:
 		return 'h';
+	case VAProfileAV1Profile0:
+		/*
+		 * ampere-av1-enablement Phase 2: RK3588 vpu981 dedicated
+		 * AV1 hantro instance. 'a' kind dispatches to
+		 * driver_data->video_fd_vpu981. On hosts without the AV1
+		 * instance the fd stays -1 and RequestQueryConfigProfiles
+		 * never enumerates AV1, so this branch is unreachable for
+		 * non-RK3588 hosts.
+		 */
+		return 'a';
 	default:
 		return '?';
 	}
@@ -448,6 +461,44 @@ int request_switch_device_for_profile(struct request_data *driver_data,
 		kind = 'p';
 	}
 
+#ifdef HAVE_DAEDALUS_V4L2
+	/*
+	 * LIBVA-1: VP9/AV1/H.264 → daedalus_v4l2 when the daemon-backed
+	 * decoder fd is open.  Pi 5 has no rkvdec (those profiles map to
+	 * 'r' by default → video_fd_rkvdec = -1 → "stay on whatever's
+	 * active" fallback would put H.264 frames on rpi-hevc-dec's fd
+	 * and S_FMT would fail).  Re-route to the daedalus daemon instead.
+	 *
+	 * HEVC stays on 'p' (rpi-hevc-dec is HEVC-only — daedalus would
+	 * accept it via FFmpeg, but rpi-hevc-dec has the GPU-backed
+	 * hardware path so it's the right choice on this SoC).
+	 *
+	 * AV1 'a' kind (RK3588 vpu981) wins ONLY if vpu981 was probed.
+	 * On a Pi 5 the vpu981 slot stays -1, so we still route AV1 to
+	 * daedalus here.  Check video_fd_vpu981 to preserve the RK3588
+	 * priority for that case.
+	 */
+	if (driver_data->video_fd_daedalus >= 0 &&
+	    driver_data->media_fd_daedalus >= 0) {
+		switch (profile) {
+		case VAProfileH264Main:
+		case VAProfileH264High:
+		case VAProfileH264ConstrainedBaseline:
+		case VAProfileH264MultiviewHigh:
+		case VAProfileH264StereoHigh:
+		case VAProfileVP9Profile0:
+			kind = 'd';
+			break;
+		case VAProfileAV1Profile0:
+			if (driver_data->video_fd_vpu981 < 0)
+				kind = 'd';
+			break;
+		default:
+			break;
+		}
+	}
+#endif
+
 	if (kind == 'r') {
 		target_video = driver_data->video_fd_rkvdec;
 		target_media = driver_data->media_fd_rkvdec;
@@ -457,6 +508,14 @@ int request_switch_device_for_profile(struct request_data *driver_data,
 	} else if (kind == 'p') {
 		target_video = driver_data->video_fd_rpi_hevc_dec;
 		target_media = driver_data->media_fd_rpi_hevc_dec;
+	} else if (kind == 'a') {
+		target_video = driver_data->video_fd_vpu981;
+		target_media = driver_data->media_fd_vpu981;
+#ifdef HAVE_DAEDALUS_V4L2
+	} else if (kind == 'd') {
+		target_video = driver_data->video_fd_daedalus;
+		target_media = driver_data->media_fd_daedalus;
+#endif
 	} else {
 		return -1;
 	}
@@ -646,6 +705,10 @@ VAStatus VA_DRIVER_INIT_FUNC(VADriverContextP context)
 	driver_data->media_fd_hantro = -1;
 	driver_data->video_fd_rpi_hevc_dec = -1;
 	driver_data->media_fd_rpi_hevc_dec = -1;
+	driver_data->video_fd_daedalus = -1;
+	driver_data->media_fd_daedalus = -1;
+	driver_data->video_fd_vpu981 = -1;
+	driver_data->media_fd_vpu981 = -1;
 
 	/*
 	 * iter38: probe BOTH rkvdec and hantro-vpu so a single libva session
@@ -677,14 +740,35 @@ VAStatus VA_DRIVER_INIT_FUNC(VADriverContextP context)
 				driver_data->video_fd_hantro = video_fd;
 				driver_data->media_fd_hantro = media_fd;
 			} else if (strcmp(info.driver, "rpi-hevc-dec") == 0) {
-				/* iter40: Pi 5 / CM5 — sole decoder is rpi-hevc-dec.
-				 * No alt driver to probe; the rkvdec / hantro slots
-				 * stay -1 and HEVC routes to 'p' via
-				 * request_device_kind_for_profile. */
+				/* iter40 + LIBVA-1: Pi 5 / CM5.  rpi-hevc-dec is
+				 * HEVC-only.  If daedalus_v4l2 is ALSO loaded (Pi 5
+				 * mixed deployment — out-of-tree daemon-backed
+				 * decoder for VP9/AV1/H264), pick it up as the alt
+				 * so VP9/AV1/H264 have somewhere to land. */
 				primary_driver = "rpi-hevc-dec";
+#ifdef HAVE_DAEDALUS_V4L2
+				alt_driver = "daedalus_v4l2";
+#else
 				alt_driver = NULL;
+#endif
 				driver_data->video_fd_rpi_hevc_dec = video_fd;
 				driver_data->media_fd_rpi_hevc_dec = media_fd;
+#ifdef HAVE_DAEDALUS_V4L2
+			} else if (strcmp(info.driver, "daedalus_v4l2") == 0) {
+				/* phase 8.10 + LIBVA-1: Pi 5 daemon-backed decoder.
+				 * VP9 / AV1 / H.264 route through it via the 'd'
+				 * kind below.  On a mixed-driver box where
+				 * rpi-hevc-dec is ALSO loaded, pick it up as the
+				 * alt so HEVC has somewhere to land too — find_
+				 * codec_device's known_decoder_drivers[] order
+				 * normally puts rpi-hevc-dec first (we hit the
+				 * other branch in practice), but symmetric handling
+				 * keeps us correct if probe order ever flips. */
+				primary_driver = "daedalus_v4l2";
+				alt_driver = "rpi-hevc-dec";
+				driver_data->video_fd_daedalus = video_fd;
+				driver_data->media_fd_daedalus = media_fd;
+#endif
 			}
 		}
 
@@ -696,15 +780,38 @@ VAStatus VA_DRIVER_INIT_FUNC(VADriverContextP context)
 				int alt_v = open(alt_video, O_RDWR | O_NONBLOCK);
 				int alt_m = (alt_v >= 0) ? open(alt_media, O_RDWR | O_NONBLOCK) : -1;
 				if (alt_v >= 0 && alt_m >= 0) {
+					/* Dispatch into the matching per-driver slot.
+					 * iter38 only had rkvdec/hantro pairs; iter40 +
+					 * LIBVA-1 extended this to rpi-hevc-dec and
+					 * daedalus_v4l2 for the Pi 5 mixed-decoder
+					 * deployment. */
 					if (strcmp(alt_driver, "rkvdec") == 0) {
 						driver_data->video_fd_rkvdec = alt_v;
 						driver_data->media_fd_rkvdec = alt_m;
-					} else {
+					} else if (strcmp(alt_driver, "hantro-vpu") == 0) {
 						driver_data->video_fd_hantro = alt_v;
 						driver_data->media_fd_hantro = alt_m;
+					} else if (strcmp(alt_driver, "rpi-hevc-dec") == 0) {
+						driver_data->video_fd_rpi_hevc_dec = alt_v;
+						driver_data->media_fd_rpi_hevc_dec = alt_m;
+#ifdef HAVE_DAEDALUS_V4L2
+					} else if (strcmp(alt_driver, "daedalus_v4l2") == 0) {
+						driver_data->video_fd_daedalus = alt_v;
+						driver_data->media_fd_daedalus = alt_m;
+#endif
+					} else {
+						/* Shouldn't happen — primary_driver branches
+						 * above only set alt_driver to one of the
+						 * names handled here.  Close and move on. */
+						close(alt_v);
+						close(alt_m);
+						alt_v = -1;
+						alt_m = -1;
 					}
+					if (alt_v >= 0) {
 						request_log("iter38: also opened %s decoder at %s + %s\n",
 							    alt_driver, alt_video, alt_media);
+					}
 				} else {
 					if (alt_v >= 0) close(alt_v);
 					if (alt_m >= 0) close(alt_m);
@@ -712,6 +819,61 @@ VAStatus VA_DRIVER_INIT_FUNC(VADriverContextP context)
 			}
 		}
 		(void)primary_driver;
+
+		/*
+		 * ampere-av1-enablement Phase 2: walk hantro-vpu media nodes
+		 * for a SECOND one that advertises V4L2_PIX_FMT_AV1_FRAME
+		 * (AV1F) as OUTPUT pixfmt. RK3588 has 3 hantro-vpu instances
+		 * (legacy MPEG2/VP8 decoder, vepu121 encoder, vpu981 AV1
+		 * decoder) all reporting driver="hantro-vpu" / model="hantro-
+		 * vpu" — so OUTPUT-format probe is the only reliable
+		 * disambiguator that doesn't depend on parsing card-name
+		 * strings (which are DTS-dependent). First match wins.
+		 *
+		 * On non-RK3588 hosts the slot stays -1; RequestQueryConfig
+		 * Profiles' AV1 push then no-ops because any_fd_supports_
+		 * output_format() returns false for AV1F.
+		 */
+		{
+			int i;
+			char path[32], av1_video[32];
+
+			for (i = 0; i < 16; i++) {
+				int mfd, vfd;
+				struct media_device_info info;
+
+				snprintf(path, sizeof path, "/dev/media%d", i);
+				mfd = open(path, O_RDWR | O_NONBLOCK);
+				if (mfd < 0) continue;
+				memset(&info, 0, sizeof info);
+				if (ioctl(mfd, MEDIA_IOC_DEVICE_INFO, &info) != 0 ||
+				    strcmp(info.driver, "hantro-vpu") != 0) {
+					close(mfd);
+					continue;
+				}
+				if (find_decoder_video_node_via_topology(
+					    mfd, av1_video, sizeof av1_video) != 0) {
+					close(mfd);
+					continue;
+				}
+				vfd = open(av1_video, O_RDWR | O_NONBLOCK);
+				if (vfd < 0) {
+					close(mfd);
+					continue;
+				}
+				if (!v4l2_find_format(vfd, V4L2_BUF_TYPE_VIDEO_OUTPUT, V4L2_PIX_FMT_AV1_FRAME) &&
+				    !v4l2_find_format(vfd, V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE, V4L2_PIX_FMT_AV1_FRAME)) {
+					close(vfd);
+					close(mfd);
+					continue;
+				}
+				driver_data->video_fd_vpu981 = vfd;
+				driver_data->media_fd_vpu981 = mfd;
+				request_log("ampere-av1: vpu981 AV1 decoder at %s + %s\n",
+					    av1_video, path);
+				break;
+			}
+		}
 	}
 
 	/*
@@ -737,6 +899,14 @@ VAStatus VA_DRIVER_INIT_FUNC(VADriverContextP context)
 			    driver_data->video_fd_rpi_hevc_dec,
 			    driver_data->media_fd_rpi_hevc_dec);
 	}
+#ifdef HAVE_DAEDALUS_V4L2
+	if (driver_data->video_fd_daedalus >= 0) {
+		request_log("phase 8.10: opened daedalus_v4l2 at video_fd=%d "
+			    "media_fd=%d (Pi 5 daemon-backed VP9/AV1/H264)\n",
+			    driver_data->video_fd_daedalus,
+			    driver_data->media_fd_daedalus);
+	}
+#endif
 
 	status = VA_STATUS_SUCCESS;
 	goto complete;
@@ -784,6 +954,20 @@ VAStatus RequestTerminate(VADriverContextP context)
 		close(driver_data->video_fd_hantro);
 	if (driver_data->media_fd_hantro >= 0)
 		close(driver_data->media_fd_hantro);
+	if (driver_data->video_fd_rpi_hevc_dec >= 0)
+		close(driver_data->video_fd_rpi_hevc_dec);
+	if (driver_data->media_fd_rpi_hevc_dec >= 0)
+		close(driver_data->media_fd_rpi_hevc_dec);
+	if (driver_data->video_fd_vpu981 >= 0)
+		close(driver_data->video_fd_vpu981);
+	if (driver_data->media_fd_vpu981 >= 0)
+		close(driver_data->media_fd_vpu981);
+#ifdef HAVE_DAEDALUS_V4L2
+	if (driver_data->video_fd_daedalus >= 0)
+		close(driver_data->video_fd_daedalus);
+	if (driver_data->media_fd_daedalus >= 0)
+		close(driver_data->media_fd_daedalus);
+#endif
 	/* Fall back to direct close if neither alt fd captured the active
 	 * pair (env-override path). */
 	if (driver_data->video_fd_rkvdec < 0 && driver_data->video_fd_hantro < 0) {

src/request.h

@@ -42,7 +42,16 @@
 
 #define V4L2_REQUEST_STR_VENDOR			"v4l2-request"
 
-#define V4L2_REQUEST_MAX_PROFILES		13
+/*
+ * Sized for max-possible enumeration with iter39 Option B reverted:
+ * MPEG2(2) + H264(6 incl. Hi10P) + HEVC(2 incl. Main10) + VP8 + VP9 + AV1 = 13.
+ * The per-group guards use `if (... && index < (MAX_PROFILES - N))` where N
+ * is the push-group size, so MAX must be ≥ total+1 — 14 here. Bumping
+ * defensively now so a future re-enable of Hi10P/Main10 doesn't silently
+ * drop AV1 through the off-by-one trap that ate ampere-av1's enumeration
+ * for a week (see issue marfrit/libva-v4l2-request-fourier#2).
+ */
+#define V4L2_REQUEST_MAX_PROFILES		14
 #define V4L2_REQUEST_MAX_ENTRYPOINTS		5
 #define V4L2_REQUEST_MAX_CONFIG_ATTRIBUTES	10
 #define V4L2_REQUEST_MAX_IMAGE_FORMATS		10
@@ -87,6 +96,39 @@ struct request_data {
 	 */
 	int video_fd_rpi_hevc_dec;
 	int media_fd_rpi_hevc_dec;
+	/*
+	 * phase 8.10: fifth multi-device-probe slot for daedalus_v4l2 — the
+	 * out-of-tree V4L2 stateless decoder shim that forwards bitstream
+	 * to a userspace daemon (daedalus-v4l2 sibling repo). Daemon does
+	 * FFmpeg-software decode for VP9 / AV1 / H.264 and ships pixels
+	 * back via dmabuf into the CAPTURE buffer.  Picked up via the
+	 * same media-controller probe + known_decoder_drivers[] entry
+	 * pattern as iter40 rpi-hevc-dec.  Stays -1 on hosts without the
+	 * daedalus module loaded; HEVC routes to rpi-hevc-dec as before.
+	 *
+	 * Fields are unconditional (8 bytes per session) so the struct
+	 * layout is stable regardless of meson option.  The active
+	 * probe + dispatch code in request.c is gated by
+	 * HAVE_DAEDALUS_V4L2; when disabled the fields stay at their
+	 * -1 init and no codepath touches them.
+	 */
+	int video_fd_daedalus;
+	int media_fd_daedalus;
+	/*
+	 * ampere-av1-enablement Phase 2: fourth multi-device-probe slot
+	 * for vpu981 (RK3588's dedicated AV1 hantro instance, kernel
+	 * card="rockchip,rk3588-av1-vpu-dec", driver name "hantro-vpu" —
+	 * shared with the legacy MPEG-2/VP8/H.264 hantro). Discriminated
+	 * by V4L2_PIX_FMT_AV1_FRAME (AV1F) OUTPUT-pixfmt capability since
+	 * the driver name alone is ambiguous on RK3588. Stays -1 on hosts
+	 * without the AV1 vpu-dec.
+	 *
+	 * Named "vpu981" for consistency with the in-progress av1-iter1
+	 * operator branch (Phase 3-5 bit-exact AV1 work — when that lands
+	 * these fields receive the actual decode dispatch wiring).
+	 */
+	int video_fd_vpu981;
+	int media_fd_vpu981;
 
 	/*
 	 * iter2 (ampere-kernel-decoders campaign) — per-fd probe result

src/v4l2.c

@@ -476,12 +476,35 @@ int v4l2_set_controls(int video_fd, int request_fd,
 		      struct v4l2_ext_control *control_array,
 		      unsigned int num_controls)
 {
+	struct v4l2_ext_controls controls;
 	int rc;
 
-	rc = v4l2_ioctl_controls(video_fd, request_fd, VIDIOC_S_EXT_CTRLS,
-				 control_array, num_controls);
+	memset(&controls, 0, sizeof(controls));
+	controls.controls = control_array;
+	controls.count = num_controls;
+	if (request_fd >= 0) {
+		controls.which = V4L2_CTRL_WHICH_REQUEST_VAL;
+		controls.request_fd = request_fd;
+	}
+
+	rc = ioctl(video_fd, VIDIOC_S_EXT_CTRLS, &controls);
 	if (rc < 0) {
-		request_log("Unable to set control(s): %s\n", strerror(errno));
+		/* error_idx is the index of the first failing control;
+		 * if it equals count, the ioctl itself failed (not a
+		 * specific control payload).  Useful for triaging
+		 * which V4L2_CID_STATELESS_* the kernel rejected. */
+		if (controls.error_idx < num_controls)
+			request_log("Unable to set control(s): %s "
+				    "(error_idx=%u/%u failing_ctrl_id=0x%x size=%u)\n",
+				    strerror(errno),
+				    controls.error_idx, controls.count,
+				    control_array[controls.error_idx].id,
+				    control_array[controls.error_idx].size);
+		else
+			request_log("Unable to set control(s): %s "
+				    "(error_idx=%u/%u ioctl-level)\n",
+				    strerror(errno),
+				    controls.error_idx, controls.count);
 		return -1;
 	}