stos: hal: Add MMIO helpers

Signed-off-by: Chloe M. <chloe@mensia.org>

paw/stos/head/hal/mmio.h

@@ -0,0 +1,48 @@
+/*
+ * Copyright (c) 2026, Chloe M.
+ * Provided under the BSD-3 clause.
+ *
+ * Description: MMIO helpers
+ * Author:      Chloe M.
+ */
+
+#ifndef _MU_MMIO_H_
+#define _MU_MMIO_H_ 1
+
+#include <stdef.h>
+
+/* Builds mmio_write<n> functions */
+#define _MMIO_WRITE_BUILDER(NAME, TYPE)         \
+    static inline void                          \
+    MMIO##NAME(volatile TYPE *ptr, TYPE val)   \
+    {                                           \
+        BARRIER();                            \
+        *(volatile TYPE *)ptr = val;            \
+    }
+
+/* Builds mmio_read<n> functions */
+#define _MMIO_READ_BUILDER(NAME, TYPE)      \
+    static inline TYPE                      \
+    MMIO##NAME(volatile TYPE *ptr)          \
+    {                                       \
+        BARRIER();                        \
+        return *(volatile TYPE *)ptr;       \
+    }
+
+/* mmio_write<n> */
+_MMIO_WRITE_BUILDER(Write8, UCHAR);
+_MMIO_WRITE_BUILDER(Write16, USHORT);
+_MMIO_WRITE_BUILDER(Write32, ULONG);
+#if __SIZEOF_SIZE_T__ == 8
+_MMIO_WRITE_BUILDER(Write64, UQUAD);
+#endif
+
+/* Builds mmio_read<n> functions */
+_MMIO_READ_BUILDER(Read8, UCHAR);
+_MMIO_READ_BUILDER(Read16, USHORT);
+_MMIO_READ_BUILDER(Read32, ULONG);
+#if __SIZEOF_SIZE_T__ == 8
+_MMIO_READ_BUILDER(Read64, UQUAD);
+#endif
+
+#endif  /* !_MU_MMIO_H_ */