feat: port ring_buf (sys/ring_buffer.h) + pre-public copyright audit (#45)

components/zkernel/CMakeLists.txt

@@ -5,6 +5,7 @@ set(srcs
     "src/k_event.c"
     "src/k_thread.c"
     "src/k_work.c"
+    "src/ring_buf.c"
     "src/sys_init.c"
     "src/fatal.c"
 )

components/zkernel/Kconfig

@@ -1,5 +1,16 @@
 menu "Boreas Kernel (zkernel)"
 
+    config RING_BUFFER_LARGE
+        bool "Use 32-bit ring buffer indices"
+        default n
+        help
+            Widens the ring buffer index type from uint16_t to uint32_t,
+            raising the maximum ring_buf capacity from 32767 bytes to
+            ~2 GiB at the cost of 12 extra bytes per struct ring_buf
+            (six index fields widen by 2 bytes each; 20 -> 32 bytes on
+            the 32-bit target). Mirrors upstream Zephyr's
+            CONFIG_RING_BUFFER_LARGE.
+
     config ZKERNEL_MUTEX_DEBUG
         bool "Enable mutex lock-ordering assertions"
         default n

components/zkernel/include/boreas/zephyr/sys/__assert.h

@@ -0,0 +1,33 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ * Copyright 2026 Intercreate
+ *
+ * Zephyr-compatible runtime assertions (upstream <zephyr/sys/__assert.h>
+ * spellings).
+ *
+ * Divergence: upstream compiles these out unless CONFIG_ASSERT=y
+ * (default n); Boreas keeps them always on -- they log and abort.
+ * NOT safe from IRAM ISR context (ESP_LOGE + abort are flash-resident).
+ * Use k_panic() (sys/util.h) for unrecoverable errors in ISR/IRAM
+ * context.
+ */
+
+#pragma once
+
+#ifndef __ASSERT
+#include <stdlib.h> /* abort() */
+
+#include "esp_log.h"
+#define __ASSERT(cond, msg)                                                                        \
+	do {                                                                                       \
+		if (!(cond)) {                                                                     \
+			ESP_LOGE("ASSERT", "%s at %s:%d", (msg), __FILE__, __LINE__);              \
+			abort();                                                                   \
+		}                                                                                  \
+	} while (0)
+#endif
+
+/* Assertion with no message (upstream spelling). */
+#ifndef __ASSERT_NO_MSG
+#define __ASSERT_NO_MSG(cond) __ASSERT((cond), "")
+#endif

components/zkernel/include/boreas/zephyr/sys/byteorder.h

@@ -1,9 +1,13 @@
 /*
  * SPDX-License-Identifier: Apache-2.0
- * Copyright 2026 Intercreate
+ * Copyright (c) 2015-2016 Intel Corporation   (upstream Zephyr)
+ * Copyright 2026 Intercreate                  (Boreas)
  *
  * Zephyr-compatible byte-order helpers for little- and big-endian
- * 16- and 32-bit access over byte buffers.
+ * 16- and 32-bit access over byte buffers. The big/little-endian
+ * 32-bit composition mirrors upstream's canonical chaining closely
+ * enough to retain the upstream copyright; the 16-bit leaf functions
+ * are independently written.
  *
  * @note Upstream Zephyr also provides 24/48/64-bit variants
  *       (sys_{get,put}_{le,be}{24,48,64}). These are intentionally