From 35715d150185c1983c4b3838c4ec80065a960cee Mon Sep 17 00:00:00 2001
From: Curle <curle@gemwire.uk>
Date: Mon, 31 Aug 2020 21:51:07 +0100
Subject: [PATCH] Add MMIO read/write functions.

---
 chroma/inc/kernel/system/io.h |  8 ++++++++
 chroma/system/rw.c            | 28 ++++++++++++++++++++++++++++
 2 files changed, 36 insertions(+)

diff --git a/chroma/inc/kernel/system/io.h b/chroma/inc/kernel/system/io.h
index 909eef8..72af83c 100644
--- a/chroma/inc/kernel/system/io.h
+++ b/chroma/inc/kernel/system/io.h
@@ -5,6 +5,8 @@
  ***     Chroma       ***
  ***********************/
 
+#define PAUSE   __asm__ __volatile__("pause")
+
 uint8_t kbdSBuffer[8];
 uint8_t InputBuffer[128];
 
@@ -37,6 +39,10 @@ void        WriteTSR(uint16_t TSRData);
 
 uint32_t    ReadPort(uint16_t Port, int Length);
 uint32_t    WritePort(uint16_t Port, uint32_t Data, int Length);
+      
+size_t      ReadMMIO(size_t Address, int Length);
+void        WriteMMIO(size_t Address, size_t Data, int Length);
+
 size_t      ReadModelSpecificRegister(size_t MSR);
 size_t      WriteModelSpecificRegister(size_t MSR, size_t Data);
 
@@ -52,6 +58,8 @@ size_t      WriteControlRegister(int CRX, size_t Data);
 size_t      ReadExtendedControlRegister(size_t XCRX);
 size_t      WriteExtendedControlRegister(size_t XCRX, size_t Data);
 
+void        InvalidatePage(size_t Page);
+
 // XCS = Extended Code Segment
 size_t      ReadXCS(void);
 
diff --git a/chroma/system/rw.c b/chroma/system/rw.c
index aa161ea..d1b2ff6 100644
--- a/chroma/system/rw.c
+++ b/chroma/system/rw.c
@@ -7,6 +7,9 @@
 
 /* This file serves to allow us to communicate with the computer through raw I/O.
  * It provides interfaces for Ports and commonly used Registers (Control Registers, Model-Specific Registers, GDT, IDT..)
+ * 
+ * Additionally, there are wrapper functions for MMIO accesses.
+ * 
  */
 
 uint32_t ReadPort(uint16_t Port, int Length) {
@@ -41,6 +44,31 @@ uint32_t WritePort(uint16_t Port, uint32_t Data, int Length) {
     return Data;
 }
 
+size_t ReadMMIO(size_t Address, int Length) {
+    if (Length == 1) {
+        return *((volatile uint8_t*)(Address));
+    } else if (Length == 2) {
+        return *((volatile uint16_t*)(Address));
+    } else if (Length == 4) {
+        return *((volatile uint32_t*)(Address));
+    } else {
+        return *((volatile size_t*)(Address));
+    }
+}
+
+void WriteMMIO(size_t Address, size_t Data, int Length) {
+    if(Length == 1) {
+        (*((volatile uint8_t*)(Address))) = ((uint8_t) Data);
+    } else if (Length == 2) {
+        (*((volatile uint16_t*)(Address))) = ((uint16_t) Data);
+    } else if (Length == 4) {
+        (*((volatile uint32_t*)(Address))) = ((uint32_t) Data);
+    } else {
+        (*((volatile uint8_t*)(Address))) = (Data);
+    } 
+}
+
+
 size_t ReadModelSpecificRegister(size_t MSR) {
     size_t RegHigh = 0, RegLow = 0;