Initial work on video driver and refactoring

build.sh

@@ -1,6 +1,8 @@
 #!/bin/bash
-i386-elf-gcc -ffreestanding -c src/kernel/main.c -o kernel.o
+i386-elf-gcc -ffreestanding -I src/ -c src/kernel/main.c -o kernel.o
+i386-elf-gcc -ffreestanding -I src/ -c src/kernel/drivers/vga/screen.c -o screen.o
+i386-elf-gcc -ffreestanding -I src/ -c src/kernel/drivers/ports/ports.c -o ports.o
 nasm -f elf src/entrypoint.s -o entry.o
 nasm -f bin src/boot/mbr.s -o mbr.bin
-i386-elf-ld -o kernel.bin -Ttext 0x1000 entry.o kernel.o --oformat binary
+i386-elf-ld -o kernel.bin -Ttext 0x1000 entry.o kernel.o ports.o screen.o --oformat binary
 cat mbr.bin kernel.bin > os.bin

src/boot/mbr.s

@@ -42,9 +42,9 @@ load_kernel:    ; Loads the kernel into memory
 
 ; Here we define our variables: They need to be defined after the
 ; halting because otherwise they will be executed as code
-real_mode_msg: db "Booted in real mode", 0
+real_mode_msg: db "TSOS is starting up", 0
 protected_mode_msg: db "Switched to protected mode", 0
-loading_kernel_msg: db "Loading kernel", 0
+loading_kernel_msg: db "Loading kernel into memory", 0
 boot_drive: db 0
 
 
@@ -55,7 +55,7 @@ BEGIN_32BIT: ; After the switch we will get here
     ; to add to the start of the video memory that
     ; is added before writing. We skip the first
     ; 320 bytes so that we don't overwrite the log
-    ; messages we may have written beforehand
+    ; messages we have already written
     mov ecx, 0x140
     call vga_println
     call kernel_offset

src/kernel/drivers/ports/ports.c

@@ -1,30 +1,31 @@
-// Implementation of a simple video driver using VGA text mode
-#include "video.h"
+// Utilities for writing to and reading from I/O ports
+
+#include "ports.h"
 
 
-uchar_t vga_readb(u16_t port) {
+byte vga_readb(u16 port) {
     // Reads a byte from the specified I/O port
-    uchar_t result;
+    byte result;
     __asm__("in %%dx, %%al" : "=a" (result) : "d" (port));
     return result;
 }
 
 
-void vga_writeb(u16_t port, uchar_t data) {
-    // Writes a byte from the specified I/O port
+void vga_writeb(u16 port, byte data) {
+    // Writes a byte to the specified I/O port
     __asm__("out %%al, %%dx" : : "a" (data), "d" (port));
 }
 
 
-u16_t vga_writew(u16_t port) {
+u16 vga_readw(u16 port) {
     // Reads a word (16 bits) from the specified I/O port
-    u16_t result;
+    u16 result;
     __asm__("in %%dx, %%ax" : "=a" (result) : "d" (port));
     return result;
 }
 
 
-void vga_readw(u16_t port, u16_t data) {
+void vga_writew(u16 port, u16 data) {
     // Writes a word (16 bits) to the specified I/O port
     __asm__("out %%ax, %%dx" : : "a" (data), "d" (port));
 }

src/kernel/drivers/ports/ports.h

@@ -0,0 +1,16 @@
+#ifndef TSOS_DRV_PORTS_H 
+#define TSOS_DRV_PORTS_H
+
+
+#define VMEM_ADDR 0xb8000
+#include "kernel/ktypes.h"
+
+
+byte vga_readb(u16 port);
+void vga_writeb(u16 port, byte data);
+u16 vga_readw(u16 port);
+void vga_writew(u16 port, u16 data);
+
+
+
+#endif

src/kernel/drivers/vga/screen.c

@@ -0,0 +1,2 @@
+// Implementation of a simple text-only VGA driver
+#include "screen.h"

src/kernel/drivers/vga/screen.h

@@ -0,0 +1,23 @@
+#ifndef TSOS_DRV_VGA_SCREEN
+#define TSOS_DRV_VGA_SCREEN
+
+#define VMEM_ADDRESS 0xb8000
+#define MAX_ROWS 25
+#define MAX_COLS 80
+#define LIGHT_GREY_ON_BLACK 0x07
+#define RED_ON_WHITE 0xf4
+
+// VGA I/O ports
+#define REG_SCREEN_CTRL 0x3d4
+#define REG_SCREEN_DATA 0x3d5
+
+#include "kernel/ktypes.h"
+#include "kernel/drivers/ports/ports.h"
+
+// Exposed API
+void clear_screen(void);
+void kprint_at(char *message, int col, int row);
+void kprint(char *message);
+
+
+#endif

src/kernel/drivers/vga/video.h

@@ -1,14 +0,0 @@
-#ifndef TSOS_DRV_VGA_H  // Avoid nasty double-inclusion problems
-#define TSOS_DRV_VGA_H
-#define VMEM_ADDR 0xb8000
-#include "../../types/ktypes.h"
-
-
-uchar_t vga_writeb(u16_t port);
-void vga_readb(u16_t port, uchar_t data);
-u16_t vga_writew(u16_t port);
-void vga_readw(u16_t port, u16_t data);
-
-
-
-#endif

src/kernel/ktypes.h

@@ -0,0 +1,13 @@
+// Shorthand definitions of various types
+// used in the kernel
+#ifndef TSOS_KTYPES
+#define TSOS_KTYPES
+
+
+typedef unsigned char byte;
+typedef unsigned short int u16;
+typedef short int i16;
+typedef unsigned int uint;
+
+
+#endif

src/kernel/main.c

@@ -1,14 +1,35 @@
 // Entry point of the TSOS kernel
-#include "types/ktypes.h"
-#include "drivers/vga/video.h"
+#include "kernel/ktypes.h"
+#include "kernel/drivers/vga/screen.h"
 
 
 void kmain(void) {
-    char_t* vbuf = (char_t*)VMEM_ADDR;
-    vbuf += 480;    // We skip the log messages before us
-    char_t *s = "Hello from the TSOS kernel!";
-    for (int_t i = 0; s[i] != '\0'; i++) {
-        *vbuf = s[i];
-        vbuf += 2;
+    byte* vga = (byte*)VMEM_ADDRESS;
+    vga_writeb(0x3d4, 14);  // We request the high byte of cursor position on port 0x3D4
+    int cursor = vga_readb(0x3d5); // And now we read it
+    // Since this is the high byte, we shift the
+    // cursor by 8 bits to make room for the low 
+    // byte
+    cursor <<= 8;
+    // Now we request the low byte
+    vga_writeb(0x3d4, 15);
+    // And we add it to the cursor
+    cursor += vga_readb(0x3d5);
+    // VGA 'cells' are 2 bytes long, but
+    // the cursor counts cells as a unit,
+    // so we multiply it by 2
+    cursor *= 2;
+    // We add 160 because when we print a 
+    // message via VGA in the bootloader,
+    // and that leaves the cursor in the
+    // wrong position
+    cursor += 160;
+    // Now we write some message onto the screen
+    byte *s = "TSOS Kernel started";
+    for (int i = 0; s[i] != '\0'; i++) {
+        vga[cursor] = s[i];  // We set the character code we want
+        cursor++;
+        vga[cursor] = 0x07;  // Light grey on black
+        cursor++;
     }
 }

src/kernel/types/ktypes.h

@@ -1,15 +0,0 @@
-// Shorthand definitions of various types
-// used in the kernel
-#ifndef TSOS_KTYPES
-#define TSOS_KTYPES
-
-
-typedef unsigned char uchar_t;
-typedef unsigned short int u16_t;
-typedef short int i16_t;
-typedef char char_t;
-typedef unsigned int uint_t;
-typedef int int_t;
-
-
-#endif