fdt: Add reg property parsing helper

1 files changed, 32 insertions, 0 deletions

diff --git a/src/fdt.zig b/src/fdt.zig
index b97e890..3ec3fda 100644
--- a/src/fdt.zig
+++ b/src/fdt.zig
@@ -24,6 +24,11 @@ pub const MemReservation = struct {
     size: u64,
 };
 
+pub const Reg = struct {
+    start: usize,
+    len: usize,
+};
+
 pub const Tree = union {
     nodes: std.ArrayList(Node),
 };
@@ -54,6 +59,33 @@ pub const Node = struct {
     pub fn isCompatible(self: Node, with: []const u8) bool {
         return self.preferredDriver([]const u8{with}) != null;
     }
+
+    pub fn reg(self: Node, allocator: std.mem.Allocator) ?std.ArrayList(Reg) {
+        const address_cells_bytes = self.parent.props.get("#address-cells");
+        const size_cells_bytes = self.parent.props.get("#size-cells");
+
+        const address_cells = if (address_cells_bytes) |bytes| std.mem.readInt(u32, bytes[0..4], .Big) else 2;
+        const size_cells = if (size_cells_bytes) |bytes| std.mem.readInt(u32, bytes[0..4], .Big) else 1;
+
+        const reg_prop = self.props.get("reg") orelse return null;
+        const reg_elem_len = 4 * address_cells + 4 * size_cells;
+
+        const n = reg_prop.len / reg_elem_len;
+
+        const regs = std.ArrayList(Reg).init(allocator);
+
+        for (0..n) |i| {
+            const start_offset = i * reg_elem_len;
+            const len_offset = start_offset + 4 * address_cells;
+
+            regs.append(.{
+                .start = std.mem.readVarInt(usize, reg[start_offset .. start_offset + 4 * address_cells], .Big),
+                .len = std.mem.readVarInt(usize, reg[len_offset .. len_offset + 4 * size_cells], .Big),
+            });
+        }
+
+        return regs;
+    }
 };
 
 pub const Property = struct {