Debug helpers

src/kernel/drivers/vga.c

@@ -0,0 +1,73 @@
+#include <vga.h>
+#include <memory.h>
+#include <ports.h>
+
+#define VGA_COLS 80
+#define VGA_ROWS 24
+#define VGA_SIZE (VGA_COLS*VGA_ROWS)
+
+#define VGA_ROW(pos) ((pos)/VGA_COLS)
+#define VGA_COL(pos) ((pos)%VGA_COLS)
+#define VGA_POS(row, col) ((row)*VGA_COLS + (col))
+
+#define VGA_ADDRESS_PORT 0x3D4
+#define VGA_DATA_PORT 0x3D5
+#define VGA_REGISTER_CURSOR_POS_LOW 0xF
+#define VGA_REGISTER_CURSOR_POS_HIGH 0xE
+
+void *vidmem;
+struct vga_cell{
+    uint8_t c;
+    uint8_t f;
+}__attribute__((packed));
+
+struct vga_cell buffer[VGA_SIZE];
+
+uint64_t cursor;
+uint8_t format;
+
+void vga_init()
+{
+    vidmem = VGA_MEMORY;
+    memset(vidmem, 0, VGA_SIZE*sizeof(struct vga_cell));
+
+    format = 0x07;
+}
+
+void movecursor()
+{
+    outb(VGA_ADDRESS_PORT, VGA_REGISTER_CURSOR_POS_LOW);
+    outb(VGA_DATA_PORT, (uint8_t)(cursor & 0xFF));
+    outb(VGA_ADDRESS_PORT, VGA_REGISTER_CURSOR_POS_HIGH);
+    outb(VGA_DATA_PORT, (uint8_t)((cursor >> 8) & 0xFF));
+}
+
+void flush()
+{
+    memcpy(vidmem, buffer, sizeof(buffer));
+}
+
+void scroll()
+{
+    while(cursor >= VGA_SIZE)
+    {
+        memmove(buffer, &buffer[VGA_POS(1,0)], VGA_COLS*(VGA_ROWS-1)*sizeof(struct vga_cell));
+        memset(&buffer[VGA_POS(VGA_ROWS-1, 0)], 0, VGA_COLS*sizeof(struct vga_cell));
+        cursor -= VGA_COLS;
+    }
+}
+
+void vga_write(char c)
+{
+    switch(c)
+    {
+        case '\n':
+            cursor += VGA_COLS - VGA_COL(cursor);
+            break;
+        default:
+            buffer[cursor++] = (struct vga_cell){.c = c, .f = format};
+    }
+    scroll();
+    flush();
+    movecursor();
+}