feat: implement DeviceNode and FdtManager classes for device tree management

1 files changed, 166 insertions, 0 deletions

diff --git a/na/fdt/device_node.cc b/na/fdt/device_node.cc
new file mode 100644
index 0000000..0c8ad46
--- /dev/null
+++ b/na/fdt/device_node.cc
@@ -0,0 +1,166 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/* Copyright (C) 2026 Richard Qin */
+
+/*
+ * device_node.cc — DeviceNode implementation
+ *
+ * Provides property lookup and child traversal for the unflattened
+ * device tree.  After construction, the tree is globally read-only.
+ *
+ * Reference: docs/specs/fdt.md §3.2
+ */
+
+#include <lume/device_node.h>
+
+/* Minimal strcmp — no lib dependency */
+static bool str_eq(const char *a, const char *b)
+{
+    while (*a && *a == *b) { a++; b++; }
+    return *a == *b;
+}
+
+/* ------------------------------------------------------------------ */
+/*  Construction / Destruction                                        */
+/* ------------------------------------------------------------------ */
+
+DeviceNode::DeviceNode(DeviceNode *parent, const char *name)
+    : name_(name), parent_(parent)
+{
+    children_list_.init();
+    props_list_.init();
+    sibling_link_.init();
+}
+
+DeviceNode::~DeviceNode()
+{
+    /* Recursively delete children */
+    list_node *cur = children_list_.next;
+    while (cur != &children_list_) {
+        list_node *next = cur->next;
+        /* Recover DeviceNode* from sibling_link_ offset */
+        DeviceNode *child = list_entry<DeviceNode, &DeviceNode::sibling_link_>(cur);
+        delete child;
+        cur = next;
+    }
+
+    /* Delete properties */
+    list_node *pc = props_list_.next;
+    while (pc != &props_list_) {
+        list_node *pn = pc->next;
+        FdtProperty *prop = reinterpret_cast<FdtProperty *>(
+            reinterpret_cast<uintptr>(pc) -
+            __builtin_offsetof(FdtProperty, link));
+        delete prop;
+        pc = pn;
+    }
+}
+
+/* ------------------------------------------------------------------ */
+/*  Tree construction (used by FdtManager::unflatten)                 */
+/* ------------------------------------------------------------------ */
+
+void DeviceNode::add_child(DeviceNode *child)
+{
+    /* Append to end of children list */
+    list_node *node = &child->sibling_link_;
+    node->prev = children_list_.prev;
+    node->next = &children_list_;
+    children_list_.prev->next = node;
+    children_list_.prev = node;
+}
+
+void DeviceNode::add_prop(FdtProperty *prop)
+{
+    list_node *node = &prop->link;
+    node->prev = props_list_.prev;
+    node->next = &props_list_;
+    props_list_.prev->next = node;
+    props_list_.prev = node;
+}
+
+/* ------------------------------------------------------------------ */
+/*  Property access                                                   */
+/* ------------------------------------------------------------------ */
+
+const FdtProperty *DeviceNode::get_prop(const char *name) const
+{
+    const list_node *cur = props_list_.next;
+    while (cur != &props_list_) {
+        const FdtProperty *prop = reinterpret_cast<const FdtProperty *>(
+            reinterpret_cast<uintptr>(cur) -
+            __builtin_offsetof(FdtProperty, link));
+        if (str_eq(prop->name, name))
+            return prop;
+        cur = cur->next;
+    }
+    return nullptr;
+}
+
+/* Big-endian helpers for decoding property values */
+static inline uint32 be32(const void *p)
+{
+    const uint8 *b = static_cast<const uint8 *>(p);
+    return (uint32(b[0]) << 24) | (uint32(b[1]) << 16) |
+           (uint32(b[2]) << 8)  |  uint32(b[3]);
+}
+
+static inline uint64 be64(const void *p)
+{
+    const uint8 *b = static_cast<const uint8 *>(p);
+    return (uint64(be32(b)) << 32) | uint64(be32(b + 4));
+}
+
+uint32 DeviceNode::get_prop_u32(const char *name, uint32 default_val) const
+{
+    const FdtProperty *p = get_prop(name);
+    if (!p || p->len < 4)
+        return default_val;
+    return be32(p->value);
+}
+
+uint64 DeviceNode::get_prop_u64(const char *name, uint64 default_val) const
+{
+    const FdtProperty *p = get_prop(name);
+    if (!p)
+        return default_val;
+    if (p->len >= 8)
+        return be64(p->value);
+    if (p->len >= 4)
+        return be32(p->value);
+    return default_val;
+}
+
+const char *DeviceNode::get_prop_string(const char *name) const
+{
+    const FdtProperty *p = get_prop(name);
+    if (!p || p->len == 0)
+        return nullptr;
+    return static_cast<const char *>(p->value);
+}
+
+/* ------------------------------------------------------------------ */
+/*  Child traversal                                                   */
+/* ------------------------------------------------------------------ */
+
+DeviceNode *DeviceNode::find_child(const char *name)
+{
+    list_node *cur = children_list_.next;
+    while (cur != &children_list_) {
+        DeviceNode *child = list_entry<DeviceNode, &DeviceNode::sibling_link_>(cur);
+        if (str_eq(child->name_, name))
+            return child;
+        cur = cur->next;
+    }
+    return nullptr;
+}
+
+void DeviceNode::for_each_child(void (*callback)(DeviceNode *))
+{
+    list_node *cur = children_list_.next;
+    while (cur != &children_list_) {
+        list_node *next = cur->next;
+        DeviceNode *child = list_entry<DeviceNode, &DeviceNode::sibling_link_>(cur);
+        callback(child);
+        cur = next;
+    }
+}