debug: debug_stream: Add debug stream record and stream header definition

This commit adds definition for abstract debug stream record and
stream header. The header file contains the necessary documentation.

Signed-off-by: Jyri Sarha <jyri.sarha@linux.intel.com>

src/include/user/debug_stream.h

@@ -0,0 +1,52 @@
+/* SPDX-License-Identifier: BSD-3-Clause
+ *
+ * Copyright(c) 2024 Intel Corporation.
+ */
+
+#ifndef __SOC_DEBUG_STREAM_H__
+#define __SOC_DEBUG_STREAM_H__
+
+/*
+ * Debug Stream is a stream protocol for passing real-time debug
+ * information from SOF system. It provides the framework for
+ * passing pieces of abstract data objects from DSP side to host side
+ * debugging tools.
+ *
+ * The details of Debug Stream protocol varies depending on transfer
+ * method, but the stream should always start with a header that
+ * consists of DEBUG_STREAM_IDENTIFIER and header size.
+ */
+
+#define DEBUG_STREAM_IDENTIFIER 0x1ED15EED /* value for 'magic' */
+
+struct debug_stream_hdr {
+	uint32_t magic;		/* Magic number to recognize stream start */
+	uint32_t hdr_size;	/* Header size */
+} __packed;
+
+/*
+ * After the header ('hdr_size' bytes from beginning of 'magic') a
+ * stream of Debug Stream records should follow. Each record will
+ * start with a record identifier and record size, after which the
+ * record payload will follow.
+ *
+ * The abstract data is application specific and is passed from DSP
+ * debug entity to user space debug tool for decoding and
+ * presentation. The data is recognized by the 'id' and the 'size_words'
+ * describes the amount of data. The 'seqno' is a running number of sent
+ * record, increased by one after each record. The protocol is
+ * agnostic about the contents of the records.
+ */
+
+struct debug_stream_record {
+	uint32_t id;		/* Record id of abstract data record */
+	uint32_t seqno;		/* Increments after each record */
+	uint32_t size_words;	/* Size of the whole record in words */
+	uint32_t data[];
+} __packed;
+
+/* Debug Stream record identifiers */
+#define DEBUG_STREAM_RECORD_ID_UNINITIALIZED	0 /* invalid record marker */
+#define DEBUG_STREAM_RECORD_ID_THREAD_INFO	1 /* Thread info record */
+
+#endif /* __SOC_DEBUG_STREAM_H__ */