Short code demonstrating how MMIO is commonly defined and accessed

mmio_mapping.h

@@ -0,0 +1,32 @@
+#include <stdint.h>
+
+// Macro for register access (volatile pointer dereferencing, not used here)
+#define REG32(addr) (*(volatile uint32_t *)(addr))
+#define REG16(addr) (*(volatile uint16_t *)(addr))
+#define REG8(addr) (*(volatile uint8_t *)(addr))
+
+typedef struct MMIO_device {
+    volatile uint16_t hello;
+    volatile uint8_t __RESERVED1[2];
+    volatile uint16_t status;
+    volatile uint8_t __RESERVED2[8];
+    volatile uint32_t control;
+    // ...and so on
+} __attribute__((aligned(4))) MMIO_device;
+
+/* A base address pointing to the start of the 'peripherals' memory region */
+#define MEM_PERIPH_BASE 0xDEADBEEF
+
+/* Specific device, often defined as an offset from a base */
+#define MY_MMIO (MEM_PERIPH_BASE + 0x10)
+
+#define DVC_CTLR_ENA (0x3 << 1) /* Device Control Register Enable */
+#define DVC_CTLR_WRITE (0x1)    /* Device Control Register Write */
+
+volatile MMIO_device *mmio1 = (volatile MMIO_device *)MY_MMIO;
+
+void configure_peripheral() {
+    mmio1->hello = 0x1234;                              // Raw write
+    mmio1->control |= DVC_CTLR_ENA | DVC_CTLR_WRITE;    // Set
+    mmio1->control &= ~(DVC_CTLR_ENA | DVC_CTLR_WRITE); // Clear
+}