Detect the VGA card before setting mode 0x13

1 files changed, 11 insertions, 1 deletions

diff --git a/src/vga.c b/src/vga.c
index e90ebba..6b093c0 100644
--- a/src/vga.c
+++ b/src/vga.c
@@ -25,9 +25,17 @@ void close_framebuffer()
     __djgpp_nearptr_disable();
 }
 
-void set_mode(uint8_t mode)
+uint8_t set_mode(uint8_t mode)
 {
     __dpmi_regs regs = { 0 };
+
+    /* detect VGA card */
+    regs.x.ax = 0x1a00;
+    __dpmi_int(0x10, &regs);
+    if (regs.h.al != 0x1a)
+        return 0;
+
+    memset(&regs, 0, sizeof(regs));
     regs.x.ax = mode;
     __dpmi_int(0x10, &regs);
 
@@ -57,6 +65,8 @@ void set_mode(uint8_t mode)
         outportw(0x3d4, 0x8e11); /* restore retrace */
         enable();
     }
+
+    return 1;
 }
 
 void wait_vsync()