staging: vboxvideo: Add page-flip support

Adds crtc page-flip support by passing the new requested framebuffer
to vbox_crtc_do_set_base().

Note there is no attempt to support vblank interrupts, it's not
not known how to do this in VBOX or if it is even possible. Since
this page-flip implementation does not try to sync the page-flip
to vertical blanking, tearing effects are possible.
Signed-off-by: Steve Longerbeam <steve_longerbeam@mentor.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/vboxvideo/vbox_mode.c

@@ -308,6 +308,31 @@ static int vbox_crtc_mode_set(struct drm_crtc *crtc,
 	return ret;
 }
 
+static int vbox_crtc_page_flip(struct drm_crtc *crtc,
+			       struct drm_framebuffer *fb,
+			       struct drm_pending_vblank_event *event,
+			       uint32_t page_flip_flags,
+			       struct drm_modeset_acquire_ctx *ctx)
+{
+	struct vbox_private *vbox = crtc->dev->dev_private;
+	struct drm_device *drm = vbox->dev;
+	unsigned long flags;
+	int rc;
+
+	rc = vbox_crtc_do_set_base(crtc, CRTC_FB(crtc), fb, 0, 0);
+	if (rc)
+		return rc;
+
+	spin_lock_irqsave(&drm->event_lock, flags);
+
+	if (event)
+		drm_crtc_send_vblank_event(crtc, event);
+
+	spin_unlock_irqrestore(&drm->event_lock, flags);
+
+	return 0;
+}
+
 static void vbox_crtc_disable(struct drm_crtc *crtc)
 {
 }
@@ -346,6 +371,7 @@ static const struct drm_crtc_funcs vbox_crtc_funcs = {
 	.reset = vbox_crtc_reset,
 	.set_config = drm_crtc_helper_set_config,
 	/* .gamma_set = vbox_crtc_gamma_set, */
+	.page_flip = vbox_crtc_page_flip,
 	.destroy = vbox_crtc_destroy,
 };