diff --git a/kernel/dma.c b/kernel/dma.c
index 6c6262f..3506fc3 100644
--- a/kernel/dma.c
+++ b/kernel/dma.c
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0
 /*
  * linux/kernel/dma.c: A DMA channel allocator. Inspired by linux/kernel/irq.c.
  *