Improved serial init handling. Optimized pushing/poping.

src/serial.asm

@@ -1,7 +1,8 @@
 SERIAL_PORT equ 0x3f8
+serialinitialized db 0
 
 serialinit:
-	pushad
+	push ax
 
 	;Disable ints
 	mov dx, SERIAL_PORT+1
@@ -46,21 +47,44 @@ serialinit:
 	out dx, al
 	in al, dx
 	cmp al, 0xae
-	jne serialiniterror
-
-
+	je .noerror
+.error:
+	push esi
+	push edi
+	push ax
+	mov esi, .errormsg
+	mov edi, 0xb8000
+	mov ah, 64
+	cld
+.errorloop:
+	lodsb
+	or al, al
+	jz .errordone
+	stosw
+	jmp .errorloop
+.errordone:
+	pop ax
+	pop edi
+	pop esi
+	jmp .end
+.noerror:
+	mov [serialinitialized], 1
 	;; Set serial to normal operation
 	mov dx, SERIAL_PORT+4
 	mov al, 0x0f
 	out dx, al
-
-	popad
+.end:
+	pop ax
 	ret
+.errormsg db "Serial init failed", 0
 
 serialwrite:
+	cmp [serialinitialized], 0
+	je .notinitialized
 	push ebp
 	mov ebp, esp
-	pushad
+	push esi
+	push ax
 	cld
 	mov esi, [ebp+8]
 .loop:
@@ -76,22 +100,9 @@ serialwrite:
 	out dx, al
 	jmp .loop
 .done:
-	popad
+	pop ax
+	pop esi
 	pop ebp
 	ret
-
-serialiniterror:
-	mov esi, .msg
-	mov edi, 0xb8000
-	mov ah, 64
-	cld
-.loop:
-	lodsb
-	or al, al
-	jz .done
-	stosw
-	jmp .loop
-.done:
-	popad
+.notinitialized:
 	ret
-.msg db "Serial init failed", 0