diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c
index a0b7576747cd..2eab714aab67 100644
--- a/drivers/tty/vt/vt.c
+++ b/drivers/tty/vt/vt.c
@@ -4279,6 +4279,44 @@ void vcs_scr_updated(struct vc_data *vc)
 	notify_update(vc);
 }
 
+void vc_scrolldelta_helper(struct vc_data *c, int lines,
+		unsigned int rolled_over, void *base, unsigned int size)
+{
+	unsigned long ubase = (unsigned long)base;
+	int margin = c->vc_size_row * 4;
+	int ul, we, p, st;
+
+	/* Turn scrollback off */
+	if (!lines) {
+		c->vc_visible_origin = c->vc_origin;
+		return;
+	}
+
+	/* Do we have already enough to allow jumping from 0 to the end? */
+	if (rolled_over > (c->vc_scr_end - ubase) + margin) {
+		ul = c->vc_scr_end - ubase;
+		we = rolled_over + c->vc_size_row;
+	} else {
+		ul = 0;
+		we = size;
+	}
+
+	p = (c->vc_visible_origin - ubase - ul + we) % we +
+		lines * c->vc_size_row;
+	st = (c->vc_origin - ubase - ul + we) % we;
+
+	/* Only a little piece would be left? Show all incl. the piece! */
+	if (st < 2 * margin)
+		margin = 0;
+	if (p < margin)
+		p = 0;
+	if (p > st - margin)
+		p = st;
+
+	c->vc_visible_origin = ubase + (p + ul) % we;
+}
+EXPORT_SYMBOL_GPL(vc_scrolldelta_helper);
+
 /*
  *	Visible symbols for modules
  */
diff --git a/drivers/usb/misc/sisusbvga/sisusb_con.c b/drivers/usb/misc/sisusbvga/sisusb_con.c
index 6331965daa0b..4b5777ec1501 100644
--- a/drivers/usb/misc/sisusbvga/sisusb_con.c
+++ b/drivers/usb/misc/sisusbvga/sisusb_con.c
@@ -686,8 +686,6 @@ static void
 sisusbcon_scrolldelta(struct vc_data *c, int lines)
 {
 	struct sisusb_usb_data *sisusb;
-	int margin = c->vc_size_row * 4;
-	int ul, we, p, st;
 
 	sisusb = sisusb_get_sisusb_lock_and_check(c->vc_num);
 	if (!sisusb)
@@ -700,39 +698,8 @@ sisusbcon_scrolldelta(struct vc_data *c, int lines)
 		return;
 	}
 
-	if (!lines)		/* Turn scrollback off */
-		c->vc_visible_origin = c->vc_origin;
-	else {
-
-		if (sisusb->con_rolled_over >
-				(c->vc_scr_end - sisusb->scrbuf) + margin) {
-
-			ul = c->vc_scr_end - sisusb->scrbuf;
-			we = sisusb->con_rolled_over + c->vc_size_row;
-
-		} else {
-
-			ul = 0;
-			we = sisusb->scrbuf_size;
-
-		}
-
-		p = (c->vc_visible_origin - sisusb->scrbuf - ul + we) % we +
-				lines * c->vc_size_row;
-
-		st = (c->vc_origin - sisusb->scrbuf - ul + we) % we;
-
-		if (st < 2 * margin)
-			margin = 0;
-
-		if (p < margin)
-			p = 0;
-
-		if (p > st - margin)
-			p = st;
-
-		c->vc_visible_origin = sisusb->scrbuf + (p + ul) % we;
-	}
+	vc_scrolldelta_helper(c, lines, sisusb->con_rolled_over,
+			(void *)sisusb->scrbuf, sisusb->scrbuf_size);
 
 	sisusbcon_set_start_address(sisusb, c);
 
diff --git a/drivers/video/console/vgacon.c b/drivers/video/console/vgacon.c
index 4c54a873452e..ede6a5a85ccd 100644
--- a/drivers/video/console/vgacon.c
+++ b/drivers/video/console/vgacon.c
@@ -332,31 +332,8 @@ static void vgacon_restore_screen(struct vc_data *c)
 
 static void vgacon_scrolldelta(struct vc_data *c, int lines)
 {
-	if (!lines)		/* Turn scrollback off */
-		c->vc_visible_origin = c->vc_origin;
-	else {
-		int margin = c->vc_size_row * 4;
-		int ul, we, p, st;
-
-		if (vga_rolled_over >
-		    (c->vc_scr_end - vga_vram_base) + margin) {
-			ul = c->vc_scr_end - vga_vram_base;
-			we = vga_rolled_over + c->vc_size_row;
-		} else {
-			ul = 0;
-			we = vga_vram_size;
-		}
-		p = (c->vc_visible_origin - vga_vram_base - ul + we) % we +
-		    lines * c->vc_size_row;
-		st = (c->vc_origin - vga_vram_base - ul + we) % we;
-		if (st < 2 * margin)
-			margin = 0;
-		if (p < margin)
-			p = 0;
-		if (p > st - margin)
-			p = st;
-		c->vc_visible_origin = vga_vram_base + (p + ul) % we;
-	}
+	vc_scrolldelta_helper(c, lines, vga_rolled_over, (void *)vga_vram_base,
+			vga_vram_size);
 	vga_set_mem_top(c);
 }
 #endif /* CONFIG_VGACON_SOFT_SCROLLBACK */
diff --git a/include/linux/vt_kern.h b/include/linux/vt_kern.h
index 6abd24f258bc..833fdd4794a0 100644
--- a/include/linux/vt_kern.h
+++ b/include/linux/vt_kern.h
@@ -191,5 +191,7 @@ extern void vt_set_led_state(int console, int leds);
 extern void vt_kbd_con_start(int console);
 extern void vt_kbd_con_stop(int console);
 
+void vc_scrolldelta_helper(struct vc_data *c, int lines,
+		unsigned int rolled_over, void *_base, unsigned int size);
 
 #endif /* _VT_KERN_H */