Make nob run display serial output to stdin

src/kernel.c

@@ -1,115 +1,19 @@
+#include "serial.h"
 #include <stdbool.h>
 #include <stddef.h>
 #include <stdint.h>
 
-/* Check if the compiler thinks you are targeting the wrong operating system. */
 #if defined(__linux__)
-#error "You are not using a cross-compiler, you will most certainly run into trouble"
+#error "Not using cross compiler"
 #endif
-
-/* This tutorial will only work for the 32-bit ix86 targets. */
 #if !defined(__i386__)
-#error "This tutorial needs to be compiled with a ix86-elf compiler"
+#error "Not using a ix86-elf compiler"
 #endif
 
-/* Hardware text mode color constants. */
-enum vga_color {
-    VGA_COLOR_BLACK = 0,
-    VGA_COLOR_BLUE = 1,
-    VGA_COLOR_GREEN = 2,
-    VGA_COLOR_CYAN = 3,
-    VGA_COLOR_RED = 4,
-    VGA_COLOR_MAGENTA = 5,
-    VGA_COLOR_BROWN = 6,
-    VGA_COLOR_LIGHT_GREY = 7,
-    VGA_COLOR_DARK_GREY = 8,
-    VGA_COLOR_LIGHT_BLUE = 9,
-    VGA_COLOR_LIGHT_GREEN = 10,
-    VGA_COLOR_LIGHT_CYAN = 11,
-    VGA_COLOR_LIGHT_RED = 12,
-    VGA_COLOR_LIGHT_MAGENTA = 13,
-    VGA_COLOR_LIGHT_BROWN = 14,
-    VGA_COLOR_WHITE = 15,
-};
-
-static inline uint8_t vga_entry_color(enum vga_color fg, enum vga_color bg) {
-    return fg | bg << 4;
-}
-
-static inline uint16_t vga_entry(unsigned char uc, uint8_t color) {
-    return (uint16_t)uc | (uint16_t)color << 8;
-}
-
-size_t strlen(const char *str) {
-    size_t len = 0;
-    while (str[len])
-        len++;
-    return len;
-}
-
-#define VGA_WIDTH 80
-#define VGA_HEIGHT 25
-#define VGA_MEMORY 0xB8000
-
-size_t terminal_row;
-size_t terminal_column;
-uint8_t terminal_color;
-uint16_t *terminal_buffer = (uint16_t *)VGA_MEMORY;
-
-void terminal_initialize(void) {
-
-    terminal_row = 0;
-    terminal_column = 0;
-    terminal_color = vga_entry_color(VGA_COLOR_LIGHT_GREY, VGA_COLOR_BLACK);
-
-    for (size_t y = 0; y < VGA_HEIGHT; y++) {
-        for (size_t x = 0; x < VGA_WIDTH; x++) {
-            const size_t index = y * VGA_WIDTH + x;
-            terminal_buffer[index] = vga_entry(' ', terminal_color);
-        }
-    }
-}
-
-void terminal_setcolor(uint8_t color) {
-    terminal_color = color;
-}
-
-void terminal_putentryat(char c, uint8_t color, size_t x, size_t y) {
-    const size_t index = y * VGA_WIDTH + x;
-    terminal_buffer[index] = vga_entry(c, color);
-}
-
-void terminal_putchar(char c) {
-    if (c == '\n') {
-        terminal_row += 1;
-        terminal_column = 0;
-        if (terminal_row == VGA_HEIGHT)
-            terminal_row = 0;
-        return;
-    }
-
-    terminal_putentryat(c, terminal_color, terminal_column, terminal_row);
-    if (++terminal_column == VGA_WIDTH) {
-        terminal_column = 0;
-        if (++terminal_row == VGA_HEIGHT)
-            terminal_row = 0;
-    }
-}
-
-void terminal_write(const char *data, size_t size) {
-    for (size_t i = 0; i < size; i++) {
-        terminal_putchar(data[i]);
-    }
-}
-
-void terminal_writestring(const char *data) {
-    terminal_write(data, strlen(data));
-}
-
 void kernel_main(void) {
-    /* Initialize terminal interface */
-    terminal_initialize();
-
-    /* Newline support is left as an exercise. */
-    terminal_writestring("Hello world!\nI'm in the kernel and no one can stop me now! =)");
+    init_serial();
+    if (!test_serial()) {
+        return;
+    }
+    send_serials("Init serial succesfully.");
 }

src/serial.h

@@ -0,0 +1,60 @@
+#ifndef SERIAL_H_
+#define SERIAL_H_
+
+#include <stdbool.h>
+#define COM1 0x3F8
+
+static inline void outb(unsigned short port, unsigned char c) {
+    __asm__ volatile("outb %0, %1" : : "a"(c), "Nd"(port));
+}
+
+static inline unsigned char inb(unsigned short port) {
+    unsigned char ret;
+    __asm__ volatile("inb %1, %0" : "=a"(ret) : "Nd"(port));
+    return ret;
+}
+
+static inline void send_serial(unsigned char c) {
+    while ((inb(COM1 + 5) & 0x20) == 0) {
+    }
+
+    outb(COM1, c);
+}
+
+static inline void send_serials(const char *str) {
+    while (*str) {
+        send_serial(*str);
+        str++;
+    }
+}
+
+static inline bool test_serial() {
+    bool to_return = true;
+    outb(COM1 + 4, 0x10);
+    send_serial(0xAE);
+
+    while ((inb(COM1 + 5) & 0x01) == 0) {
+    }
+
+    if (inb(COM1) != 0xAE)
+        to_return = false;
+
+    outb(COM1 + 4, 0x00);
+    return to_return;
+}
+
+static inline void init_serial() {
+    // Set baud rate
+    outb(COM1 + 3, 0x80); // set MSb to 1
+    outb(COM1 + 0, 0x01); // set LSB to 1 for a divisor of 1 (115200 baud rate)
+    outb(COM1 + 1, 0x00); // set MSB to 0 for a divisor of 1
+    outb(COM1 + 3, 0x00); // clean
+
+    // Configure line control register
+    outb(COM1 + 3, 0x03); // set the two LSb to 11 for a max len of 8bits
+
+    // Disable interrupts
+    outb(COM1 + 1, 0x00);
+}
+
+#endif // SERIAL_H_