1 files changed, 9 insertions, 0 deletions

diff --git a/src/mmio.c b/src/mmio.c
index 47ef354..e082d66 100644
--- a/src/mmio.c
+++ b/src/mmio.c
@@ -1,5 +1,12 @@
+/*
+References:
+  https://wiki.osdev.org/Raspberry_Pi_Bare_Bones
+  https://jsandler18.github.io/extra/peripheral.html
+  https://www.raspberrypi.org/app/uploads/2012/02/BCM2835-ARM-Peripherals.pdf
+*/
 #include <mmio.h>
 
+// Peripheral base address.
 static void* MMIO_BASE;
 
 void mmio_init(int raspi) {
@@ -11,6 +18,8 @@ void mmio_init(int raspi) {
   }
 }
 
+// All MMIO registers are 32-bit.
+
 #define REG_ADDR(reg) ((volatile uint32_t*)(MMIO_BASE + reg))
 
 uint32_t mmio_read(uint32_t reg) {