kern: os: Add MMIO helper macros

Signed-off-by: Ian Moffett <ian@osmora.org>

2 files changed, 109 insertions, 0 deletions

diff --git a/sys/inc/os/mmio.h b/sys/inc/os/mmio.h
new file mode 100644
index 0000000..443db20
--- /dev/null
+++ b/sys/inc/os/mmio.h
@@ -0,0 +1,108 @@
+/*
+ * Copyright (c) 2025 Ian Marco Moffett and the Osmora Team.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of Hyra nor the names of its
+ *    contributors may be used to endorse or promote products derived from
+ *    this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPKERNE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LKERNS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * PKERNSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef _OS_MMIO_H_
+#define _OS_MMIO_H_
+
+#include <sys/types.h>
+#include <sys/cdefs.h>
+#include <vm/vm.h>
+
+/*
+ * mmio_write<n> - Writes to MMIO address with specific size
+ *
+ * @addr: Address to write to.
+ * @val: Value to write.
+ *
+ * These functions will add the higher half
+ * offset (KERN_BASE) if the MMIO address
+ * is less than KERN_BASE as it'll be safe
+ * to assume it's a physical address. Page faults
+ * from writes could be due to the resulting virtual
+ * address not being mapped.
+ */
+#define _MMIO_WRITE_TYPE(TYPE, SUFFIX)                  \
+    static inline void                                  \
+    mmio_write##SUFFIX(volatile void *addr, TYPE val)   \
+    {                                                   \
+        uintptr_t tmp;                                  \
+                                                        \
+        tmp = (uintptr_t)addr;                          \
+        if (tmp < KERN_BASE) {                          \
+            tmp += KERN_BASE;                           \
+        }                                               \
+        *(volatile TYPE *)tmp = val;                    \
+        __barrier();                                    \
+    }
+
+/*
+ * mmio_read<n> - Does the same as mmio_write<n> but for reading
+ *
+ * @addr: Address to read from.
+ */
+#define _MMIO_READ_TYPE(TYPE, SUFFIX)                   \
+    static inline TYPE                                  \
+    mmio_read##SUFFIX(volatile void *addr)              \
+    {                                                   \
+        uintptr_t tmp;                                  \
+                                                        \
+        tmp = (uintptr_t)addr;                          \
+        if (tmp < KERN_BASE) {                          \
+            tmp += KERN_BASE;                           \
+        }                                               \
+                                                        \
+        __barrier();                                    \
+        return *(volatile TYPE *)tmp;                   \
+    }
+
+/*
+ * To write to an MMIO address of, for example,
+ * 8 bits, use mmio_write8(addr, val)
+ */
+_MMIO_WRITE_TYPE(uint8_t, 8)
+_MMIO_WRITE_TYPE(uint16_t, 16)
+_MMIO_WRITE_TYPE(uint32_t, 32)
+#if __SIZEOF_SIZE_T__ == 8
+_MMIO_WRITE_TYPE(uint64_t, 64)
+#endif
+__extension__
+
+/*
+ * To read from an MMIO address of, for example,
+ * 8 bits, use mmio_read8(addr)
+ */
+_MMIO_READ_TYPE(uint8_t, 8)
+_MMIO_READ_TYPE(uint16_t, 16)
+_MMIO_READ_TYPE(uint32_t, 32)
+#if __SIZEOF_SIZE_T__ == 8
+_MMIO_READ_TYPE(uint64_t, 64)
+#endif
+__extension__
+
+#endif  /* !_OS_MMIO_H_ */
diff --git a/sys/inc/sys/cdefs.h b/sys/inc/sys/cdefs.h
index 147d7f9..b6028f6 100644
--- a/sys/inc/sys/cdefs.h
+++ b/sys/inc/sys/cdefs.h
@@ -44,6 +44,7 @@
 #define __nothing       ((void)0)
 #define __likely(exp)   __builtin_expect(((exp) != 0), 1)
 #define __unlikely(exp) __builtin_expect(((exp) != 0), 0)
+#define __barrier()     __asmv("" ::: "memory")
 #define __static_assert _Static_assert
 
 #endif  /* !_SYS_CDEFS_H_ */