hw/i386/vmmouse:add relative packet flag for button status

The buttons value use macros instead of direct numbers.

If request relative mode, have to add this for
guest vmmouse driver to judge this is a relative packet.
otherwise,vmmouse driver will not match
the condition 'status & VMMOUSE_RELATIVE_PACKET',
and can't report events on the correct(relative) input device,
result to relative mode unuseful.

Signed-off-by: Zongmin Zhou<zhouzongmin@kylinos.cn>
Message-ID: <20230413081526.2229916-1-zhouzongmin@kylinos.cn>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>

hw/i386/vmmouse.c

@@ -44,6 +44,12 @@
 
 #define VMMOUSE_VERSION		0x3442554a
 
+#define VMMOUSE_RELATIVE_PACKET    0x00010000
+
+#define VMMOUSE_LEFT_BUTTON        0x20
+#define VMMOUSE_RIGHT_BUTTON       0x10
+#define VMMOUSE_MIDDLE_BUTTON      0x08
+
 #ifdef DEBUG_VMMOUSE
 #define DPRINTF(fmt, ...) printf(fmt, ## __VA_ARGS__)
 #else
@@ -103,15 +109,18 @@ static void vmmouse_mouse_event(void *opaque, int x, int y, int dz, int buttons_
             x, y, dz, buttons_state);
 
     if ((buttons_state & MOUSE_EVENT_LBUTTON))
-        buttons |= 0x20;
+        buttons |= VMMOUSE_LEFT_BUTTON;
     if ((buttons_state & MOUSE_EVENT_RBUTTON))
-        buttons |= 0x10;
+        buttons |= VMMOUSE_RIGHT_BUTTON;
     if ((buttons_state & MOUSE_EVENT_MBUTTON))
-        buttons |= 0x08;
+        buttons |= VMMOUSE_MIDDLE_BUTTON;
 
     if (s->absolute) {
         x <<= 1;
         y <<= 1;
+    } else{
+        /* add for guest vmmouse driver to judge this is a relative packet. */
+        buttons |= VMMOUSE_RELATIVE_PACKET;
     }
 
     s->queue[s->nb_queue++] = buttons;