add "fb" module for framebuffer control

src/fb.c

@@ -0,0 +1,30 @@
+#include "fb.h"
+
+static uint32_t * fb;
+static uint32_t fb_width;
+static uint32_t fb_height;
+static uint32_t fb_pitch;
+
+void fb_init(uint32_t * addr, uint32_t width, uint32_t height, uint32_t pitch)
+{
+    fb = addr;
+    fb_width = width;
+    fb_height = height;
+    fb_pitch = pitch;
+    for (uint32_t row = 0u; row < fb_height; row++)
+    {
+        for (uint32_t col = 0u; col < fb_width; col++)
+        {
+            uint32_t er = (col * fb_height) / fb_width;
+            int32_t dr = (int32_t)row - (int32_t)er;
+            if (dr < 0)
+            {
+                dr = -dr;
+            }
+            uint8_t r = 255u - ((uint32_t)dr * 256u / fb_height);
+            uint8_t g = col * 256u / fb_width;
+            uint8_t b = row * 256u / fb_height;
+            fb[fb_pitch * row / 4u + col] = (r << 16u) | (g << 8u) | b;
+        }
+    }
+}

src/fb.h

@@ -0,0 +1,8 @@
+#ifndef FB_H
+#define FB_H
+
+#include <stdint.h>
+
+void fb_init(uint32_t * addr, uint32_t width, uint32_t height, uint32_t pitch);
+
+#endif

src/kernel_main.c

@@ -1,9 +1,5 @@
 #include <stdint.h>
-
+#include "fb.h"
-uint32_t * fb;
-uint32_t pitch;
-uint32_t width;
-uint32_t height;
 
 static uint32_t * process_mbinfo_tag(uint32_t * mbinfo)
 {
@@ -15,10 +11,7 @@ static uint32_t * process_mbinfo_tag(uint32_t * mbinfo)
         return 0u;
 
     case 8u:
-        fb = (uint32_t *)mbinfo[2];
+        fb_init((uint32_t *)mbinfo[2], mbinfo[5], mbinfo[6], mbinfo[4]);
-        pitch = mbinfo[4];
-        width = mbinfo[5];
-        height = mbinfo[6];
         break;
     }
     return (uint32_t *)(((uint32_t)mbinfo + size + 7u) & 0xFFFFFFF8u);
@@ -37,20 +30,4 @@ static void process_mbinfo(uint32_t * mbinfo)
 void kernel_main(uint32_t * mbinfo)
 {
     process_mbinfo(mbinfo);
-    for (uint32_t row = 0u; row < height; row++)
-    {
-        for (uint32_t col = 0u; col < width; col++)
-        {
-            uint32_t er = (col * height) / width;
-            int32_t dr = (int32_t)row - (int32_t)er;
-            if (dr < 0)
-            {
-                dr = -dr;
-            }
-            uint8_t r = 255u - ((uint32_t)dr * 256u / height);
-            uint8_t g = col * 256u / width;
-            uint8_t b = row * 256u / height;
-            fb[pitch * row / 4u + col] = (r << 16u) | (g << 8u) | b;
-        }
-    }
 }