From a5fbeef6f88cb202f929d32594e27ee32c8f118f Mon Sep 17 00:00:00 2001
From: hackerman-kl <hackerman-kl@kebag-logic.com>
Date: Sun, 26 Apr 2026 14:55:25 +0200
Subject: [PATCH] milan-avb: add AVDECC stream_format decoder in aecp-aem.h

---
 src/modules/module-avb/aecp-aem.h | 74 +++++++++++++++++++++++++++++++
 1 file changed, 74 insertions(+)

diff --git a/src/modules/module-avb/aecp-aem.h b/src/modules/module-avb/aecp-aem.h
index 25b24273a..c94f416dc 100644
--- a/src/modules/module-avb/aecp-aem.h
+++ b/src/modules/module-avb/aecp-aem.h
@@ -6,8 +6,82 @@
 #ifndef AVB_AEM_H
 #define AVB_AEM_H
 
+#include <endian.h>
+#include <stdbool.h>
+#include <stdint.h>
+
 #include "aecp.h"
 #include "aecp-aem-types.h"
+#include "packets.h"
+
+/* AVDECC stream_format decoder.
+ *
+ * The 64-bit stream_format field carried in STREAM_INPUT/STREAM_OUTPUT
+ * descriptors and in SET/GET_STREAM_FORMAT is encoded per IEEE 1722-2016
+ * Section 7.3.x / Annex H — the high byte is the AVTP subtype, the lower 56 bits
+ * are subtype-specific. This struct exposes the subset needed by the data
+ * plane plus an `is_audio` shortcut so callers can skip non-media streams
+ * (CRF). Fields are 0 when not applicable.
+ *
+ * NOTE: bit-level decoding inside each subtype is incomplete. Today the
+ * decoder identifies the subtype reliably and falls back to the historical
+ * 8 ch / 48 kHz / 24-bit defaults for audio — sufficient for current Milan
+ * builds where every stream_input_0 / stream_output_0 uses one of those
+ * formats. TODO Section H.1 (AAF) and Section F (IEC 61883-6 AM824) fields once a real
+ * conformance run needs other rates / channel counts. */
+enum avb_aem_stream_format_kind {
+	AVB_AEM_STREAM_FORMAT_KIND_UNKNOWN = 0,
+	AVB_AEM_STREAM_FORMAT_KIND_AAF,
+	AVB_AEM_STREAM_FORMAT_KIND_IEC_61883_6,
+	AVB_AEM_STREAM_FORMAT_KIND_CRF,
+};
+
+struct avb_aem_stream_format_info {
+	uint8_t subtype;
+	enum avb_aem_stream_format_kind kind;
+	bool is_audio;
+	uint32_t rate;
+	uint16_t channels;
+	uint8_t bit_depth;
+	uint16_t samples_per_frame;
+};
+
+static inline void avb_aem_stream_format_decode(uint64_t fmt_be,
+		struct avb_aem_stream_format_info *out)
+{
+	uint64_t f = be64toh(fmt_be);
+	out->subtype = (uint8_t)((f >> 56) & 0xFF);
+	out->kind = AVB_AEM_STREAM_FORMAT_KIND_UNKNOWN;
+	out->is_audio = false;
+	out->rate = 0;
+	out->channels = 0;
+	out->bit_depth = 0;
+	out->samples_per_frame = 0;
+
+	switch (out->subtype) {
+	case AVB_SUBTYPE_AAF:
+		out->kind = AVB_AEM_STREAM_FORMAT_KIND_AAF;
+		out->is_audio = true;
+		out->rate = 48000;
+		out->channels = 8;
+		out->bit_depth = 24;
+		out->samples_per_frame = 6;
+		break;
+	case AVB_SUBTYPE_61883_IIDC:
+		out->kind = AVB_AEM_STREAM_FORMAT_KIND_IEC_61883_6;
+		out->is_audio = true;
+		out->rate = 48000;
+		out->channels = 8;
+		out->bit_depth = 24;
+		out->samples_per_frame = 6;
+		break;
+	case AVB_SUBTYPE_CRF:
+		out->kind = AVB_AEM_STREAM_FORMAT_KIND_CRF;
+		break;
+	default:
+		break;
+	}
+}
 
 struct avb_packet_aecp_aem_acquire {
 	uint32_t flags;