1 files changed, 158 insertions, 0 deletions
diff --git a/devices/vga.c b/devices/vga.c
new file mode 100644
index 0000000..51f860f
--- /dev/null
+++ b/devices/vga.c
@@ -0,0 +1,158 @@
+#include "vga.h"
+#include <stdint.h>
+#include <sys/io.h>
+
+#define cga_idx_port 0x3d4
+#define cga_dat_port 0x3d5
+
+#define cursor_start 0x0a
+#define cursor_end 0x0b
+#define cursor_addr_h 0x0e
+#define cursor_addr_l 0x0f
+#define cursor_hide 0x20
+
+struct __attribute__((packed)) VGAEntry {
+  char text;
+  unsigned foreground : 4;
+  unsigned background : 4;
+};
+/* TODO _Static_assert(sizeof(struct VGAEntry) == 2, "sizeof VGAEntry"); */
+
+const int width = 80;
+const int height = 25;
+
+struct VGAEntry *buffer;
+int col = 0;
+int row = 0;
+
+/* *** Cursor *** */
+void
+vga_enable_cursor(unsigned char start, unsigned char end)
+{
+  outb(cursor_start, cga_idx_port);
+  outb((inb(cga_dat_port) & 0xc0) | start, cga_dat_port);
+
+  outb(cursor_end, cga_idx_port);
+  outb((inb(cga_dat_port) & 0xe0) | end, cga_dat_port);
+}
+
+void
+vga_disable_cursor()
+{
+  outb(cursor_start, cga_idx_port);
+  outb(cursor_hide, cga_dat_port);
+}
+
+void
+vga_update_cursor(void)
+{
+  const uint16_t pos = (uint16_t)(row * width + col);
+
+  outb(cursor_addr_l, cga_idx_port);
+  outb((unsigned char)pos & 0xff, cga_dat_port);
+
+  outb(cursor_addr_h, cga_idx_port);
+  outb((unsigned char)(pos >> 8) & 0xff, cga_dat_port);
+}
+
+/* *** Text Mode Output *** */
+void
+vga_putc(__attribute__((unused)) const FILE *self, char a)
+{
+  int i, x, y;
+
+  switch (a) {
+  case '\n':
+    col = 0;
+    ++row;
+    break;
+  case '\r':
+    col = 0;
+    break;
+  case '\b':
+    --col;
+    if (col < 0) col = 0;
+    break;
+  default:
+    buffer[row * width + col].text = a;
+    ++col;
+  }
+
+  if (col == width) {
+    col = 0;
+    ++row;
+  }
+
+  if (row == height) {
+    /* scroll up */
+    for (y = 1; y < height; ++y)
+      for (x = 0; x < width; ++x) {
+        const int prev = (y - 1) * width + x;
+        const int curr = y * width + x;
+        buffer[prev] = buffer[curr];
+      }
+    /* blank out last row */
+    for (i = (height - 1) * width; i < height * width; ++i) buffer[i].text = ' ';
+    --row;
+  }
+}
+
+int
+vga_puts(const FILE *self, const char *string, int len)
+{
+  int i;
+
+  int written = 0;
+  if (len == -1)
+    while (*string != '\0') {
+      vga_putc(self, *string);
+      ++string;
+      ++written;
+    }
+
+  else
+    for (i = 0; i < len; ++i) {
+      vga_putc(self, string[i]);
+      ++written;
+    }
+  return written;
+}
+
+void
+vga_flush(__attribute__((unused)) const FILE *self)
+{
+  vga_update_cursor();
+}
+
+/* *** Text Mode *** */
+FILE vga_stream;
+
+FILE *
+vga_init(void *addr)
+{
+  buffer = (struct VGAEntry *)addr;
+  vga_enable_cursor(14, 15);
+  vga_clear(VGA_COLOR_LIGHT_BLUE, VGA_COLOR_LIGHT_GREY);
+
+  vga_stream.id = 0;
+  vga_stream.putc = &vga_putc;
+  vga_stream.puts = &vga_puts;
+  vga_stream.flush = &vga_flush;
+  return &vga_stream;
+}
+
+void
+vga_clear(enum vga_color foreground, enum vga_color background)
+{
+  int x, y;
+
+  for (y = 0; y < height; ++y)
+    for (x = 0; x < width; ++x) {
+      const int index = y * width + x;
+      buffer[index].text = ' ';
+      buffer[index].foreground = foreground;
+      buffer[index].background = background;
+    }
+  col = row = 0;
+  vga_update_cursor();
+}