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: NSimon Glass <sjg@chromium.org>

drivers/video/display-uclass.c

@@ -23,10 +23,19 @@ int display_enable(struct udevice *dev, int panel_bpp,
 			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 @@ int display_read_timing(struct udevice *dev, struct display_timing *timing)
 	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",

include/display.h

@@ -16,10 +16,12 @@ struct display_timing;
  * @source_id:	ID for the source of the display data, typically a video
  * controller
  * @src_dev:	Source device providing the video
+ * @in_use:	Display is being used
  */
 struct display_plat {
 	int source_id;
 	struct udevice *src_dev;
+	bool in_use;
 };
 
 /**
@@ -41,6 +43,14 @@ int display_read_timing(struct udevice *dev, struct display_timing *timing);
 int display_enable(struct udevice *dev, int panel_bpp,
 		   const struct display_timing *timing);
 
+/**
+ * display_in_use() - Check if a display is in use by any device
+ *
+ * @return true if the device is in use (display_enable() has been called
+ * successfully), else false
+ */
+bool display_in_use(struct udevice *dev);
+
 struct dm_display_ops {
 	/**
 	 * read_timing() - Read information directly