video: Track whether a display is in use

Mark a display as in use when display_enable() is called. This can avoid
a display being used by multiple video-output devices.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/video/display-uclass.c b/drivers/video/display-uclass.c
index e4763de..e752eb0 100644
--- a/drivers/video/display-uclass.c
+++ b/drivers/video/display-uclass.c
@@ -23,10 +23,19 @@
 			const struct display_timing *timing)
 {
 	struct dm_display_ops *ops = display_get_ops(dev);
+	struct display_plat *disp_uc_plat;
+	int ret;
 
 	if (!ops || !ops->enable)
 		return -ENOSYS;
-	return ops->enable(dev, panel_bpp, timing);
+	ret = ops->enable(dev, panel_bpp, timing);
+	if (ret)
+		return ret;
+
+	disp_uc_plat = dev_get_uclass_platdata(dev);
+	disp_uc_plat->in_use = true;
+
+	return 0;
 }
 
 int display_read_timing(struct udevice *dev, struct display_timing *timing)
@@ -48,6 +57,13 @@
 	return edid_get_timing(buf, ret, timing, &panel_bits_per_colour);
 }
 
+bool display_in_use(struct udevice *dev)
+{
+	struct display_plat *disp_uc_plat = dev_get_uclass_platdata(dev);
+
+	return disp_uc_plat->in_use;
+}
+
 UCLASS_DRIVER(display) = {
 	.id		= UCLASS_DISPLAY,
 	.name		= "display",