fresnel-fourier iter7 Phase 7 fix-forward: data links connect pads not entities directly

Empirical Phase 7 verification revealed the algorithm bug: data links
in MEDIA_IOC_G_TOPOLOGY connect PAD IDs, not entity IDs directly.
My iter7 Phase 6 commit compared link source_id/sink_id against
the proc entity_id, never matched → io_entity_ids stayed empty →
interface lookup never fired → returns -1 → falls back to legacy
hardcoded path.

Topology dump on fresnel /dev/media0 (rkvdec) confirmed:
- Entity 3 (rkvdec-proc) has function=0x4008 (DECODER) ✓
- Data link src=16777218 sink=16777220 — these are PAD ids
  (0x01000002, 0x01000004), NOT entity 3.
- Interface link src=50331660 (interface) sink=1 (entity) — for
  interface links source/sink ARE entity IDs.

Fix: resolve pads → entities via the topo.pads[] array.
1. Collect pads belonging to proc entity (via pads[].entity_id).
2. For each data link touching those pads, the OTHER pad's
   entity_id is an IO neighbor.
3. Find interface link to those IO entities (unchanged from prev).

Also allocate topo.pads[] in the 2-call ioctl pattern.

Signed-off-by: claude-noether <claude-noether@reauktion.de>

src/request.c

@@ -140,6 +140,7 @@ static int find_decoder_video_node_via_topology(int media_fd,
 	struct media_v2_entity *entities = NULL;
 	struct media_v2_interface *interfaces = NULL;
 	struct media_v2_link *links = NULL;
+	struct media_v2_pad *pads = NULL;
 	int ret = -1;
 	unsigned int i, j;
 
@@ -147,50 +148,81 @@ static int find_decoder_video_node_via_topology(int media_fd,
 	if (ioctl(media_fd, MEDIA_IOC_G_TOPOLOGY, &topo) < 0)
 		return -1;
 	if (topo.num_entities == 0 || topo.num_interfaces == 0 ||
-	    topo.num_links == 0)
+	    topo.num_links == 0 || topo.num_pads == 0)
 		return -1;
 
 	entities   = calloc(topo.num_entities,   sizeof *entities);
 	interfaces = calloc(topo.num_interfaces, sizeof *interfaces);
 	links      = calloc(topo.num_links,      sizeof *links);
-	if (!entities || !interfaces || !links)
+	pads       = calloc(topo.num_pads,       sizeof *pads);
+	if (!entities || !interfaces || !links || !pads)
 		goto out;
 
 	topo.ptr_entities   = (uintptr_t)entities;
 	topo.ptr_interfaces = (uintptr_t)interfaces;
 	topo.ptr_links      = (uintptr_t)links;
+	topo.ptr_pads       = (uintptr_t)pads;
 
 	if (ioctl(media_fd, MEDIA_IOC_G_TOPOLOGY, &topo) < 0)
 		goto out;
 
 	for (i = 0; i < topo.num_entities; i++) {
 		uint32_t proc_id;
+		uint32_t proc_pad_ids[16];
 		uint32_t io_entity_ids[16];
+		unsigned int proc_pad_count = 0;
 		unsigned int io_count = 0;
 
 		if (entities[i].function != MEDIA_ENT_F_PROC_VIDEO_DECODER)
 			continue;
 		proc_id = entities[i].id;
 
-		/* Step 2: collect data-link neighbors of the proc entity. */
+		/* Step 2a: collect pads belonging to the proc entity. Data
+		 * links connect PADs, not entities directly. */
+		for (j = 0; j < topo.num_pads; j++) {
+			if (pads[j].entity_id != proc_id)
+				continue;
+			if (proc_pad_count < (sizeof proc_pad_ids /
+					      sizeof proc_pad_ids[0]))
+				proc_pad_ids[proc_pad_count++] = pads[j].id;
+		}
+
+		/* Step 2b: walk data links. For each link with either endpoint
+		 * in proc_pad_ids[], the other endpoint is a pad belonging to
+		 * an IO neighbor. Resolve that pad's entity_id via pads[]. */
 		for (j = 0; j < topo.num_links; j++) {
-			uint32_t other;
+			uint32_t other_pad = 0;
+			unsigned int k;
 
 			if (links[j].flags & MEDIA_LNK_FL_INTERFACE_LINK)
 				continue;
-			if (links[j].source_id == proc_id)
+			for (k = 0; k < proc_pad_count; k++) {
-				other = links[j].sink_id;
+				if (links[j].source_id == proc_pad_ids[k])
-			else if (links[j].sink_id == proc_id)
+					other_pad = links[j].sink_id;
-				other = links[j].source_id;
+				else if (links[j].sink_id == proc_pad_ids[k])
-			else
+					other_pad = links[j].source_id;
+				if (other_pad != 0)
+					break;
+			}
+			if (other_pad == 0)
+				continue;
+			/* Resolve other_pad to its entity_id. */
+			for (k = 0; k < topo.num_pads; k++) {
+				if (pads[k].id != other_pad)
 					continue;
 				if (io_count < (sizeof io_entity_ids /
 						sizeof io_entity_ids[0]))
-				io_entity_ids[io_count++] = other;
+					io_entity_ids[io_count++] =
+						pads[k].entity_id;
+				break;
+			}
 		}
 
 		/* Step 3-4: find an interface link from any IO entity neighbor;
-		 * resolve devnode for the linked V4L_VIDEO interface. */
+		 * resolve devnode for the linked V4L_VIDEO interface.
+		 * Interface links connect interfaces↔entities directly (not
+		 * via pads), so source_id/sink_id is an entity ID on one side
+		 * and an interface ID on the other. */
 		for (j = 0; j < topo.num_links; j++) {
 			uint32_t intf_id = 0;
 			unsigned int k;
@@ -230,6 +262,7 @@ out:
 	free(entities);
 	free(interfaces);
 	free(links);
+	free(pads);
 	return ret;
 }
 

tests/run_perf_binding_cell.sh

@@ -171,17 +171,19 @@ run_consumer() {
 	sleep 1
 
 	# Parse pidstat by header: locate the %CPU column index from the
-	# column-name row, then apply it to data rows. Robust across
+	# column-name row (where any field equals "%CPU"), then apply it
-	# sysstat 12.x point releases (where column positions shift).
+	# to data rows. Robust across sysstat 12.x point releases.
+	# pidstat default output has no '#' header marker — the header is
+	# the first row containing "%CPU" as a field.
 	awk '
-		# Header row: find which field is %CPU.
+		# Header row: any line where some field equals "%CPU".
-		$1 == "#" {
+		!col {
-			for (i = 1; i <= NF; i++) if ($i == "%CPU") col = i
+			for (i = 1; i <= NF; i++) if ($i == "%CPU") { col = i; next }
-			next
 		}
-		# Data row: skip the average summary at end + blank lines.
+		# Data row: lines whose value at $col is numeric. Skip the
-		col && NF >= col && $1 ~ /^[0-9]/ {
+		# trailing "Average" summary by requiring $col to parse cleanly.
-			if ($col ~ /^[0-9]+(\.[0-9]+)?$/) print $col
+		col && NF >= col && $col ~ /^[0-9]+(\.[0-9]+)?$/ {
+			print $col
 		}
 	' "$logdir/pidstat.log" >"$logdir/cpu_pct.log" || true