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/* 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;
}
}
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