drm: make mode numbers no change by comparing probed modes

The mode list sets all the output modes to UNVERIFIED, then probes a new list,
If a mode is on the new list and not on the old, it adds it to the old,
if a mode is on the new list and old, it just updates the status to the new
mode status.
If a mode is on the old list and not on the new, prune invalid modes should
remove all UNVERIFIED modes

linux-core/drm_crtc.c

@@ -286,8 +286,9 @@ void drm_crtc_probe_output_modes(struct drm_device *dev, int maxX, int maxY)
 
 	list_for_each_entry(output, &dev->mode_config.output_list, head) {
 
+		/* set all modes to the unverified state */
 		list_for_each_entry_safe(mode, t, &output->modes, head)
-			drm_mode_remove(output, mode);
+			mode->status = MODE_UNVERIFIED;
 		
 		output->status = (*output->funcs->detect)(output);
 
@@ -300,9 +301,7 @@ void drm_crtc_probe_output_modes(struct drm_device *dev, int maxX, int maxY)
 		ret = (*output->funcs->get_modes)(output);
 
 		if (ret) {
-			/* move the modes over to the main mode list */
+			drm_mode_output_list_update(output);
-			drm_mode_list_concat(&output->probed_modes,
-					     &output->modes);
 		}
 
 		if (maxX && maxY)

linux-core/drm_crtc.h

@@ -59,6 +59,7 @@ enum drm_mode_status {
     MODE_ONE_HEIGHT,    /* only one height is supported */
     MODE_ONE_SIZE,      /* only one resolution is supported */
     MODE_NO_REDUCED,    /* monitor doesn't accept reduced blanking */
+    MODE_UNVERIFIED = -3, /* mode needs to reverified */
     MODE_BAD = -2,	/* unspecified reason */
     MODE_ERROR	= -1	/* error condition */
 };

linux-core/drm_modes.c

@@ -517,3 +517,42 @@ void drm_mode_sort(struct list_head *mode_list)
 {
 	list_sort(mode_list, drm_mode_compare);
 }
+
+
+/**
+ * drm_mode_output_list_update - update the mode list for the output
+ * @output: the output to update
+ *
+ * LOCKING:
+ * Caller must hold a lock protecting @mode_list.
+ *
+ * This moves the modes from the @output probed_modes list
+ * to the actual mode list. It compares the probed mode against the current
+ * list and only adds different modes. All modes unverified after this point
+ * will be removed by the prune invalid modes.
+ */
+void drm_mode_output_list_update(struct drm_output *output)
+{
+	struct drm_display_mode *mode, *t;
+	struct drm_display_mode *pmode, *pt;
+	int found_it;
+	list_for_each_entry_safe(pmode, pt, &output->probed_modes,
+				 head) {
+		found_it = 0;
+		/* go through current modes checking for the new probed mode */
+		list_for_each_entry(mode, &output->modes, head) {
+			if (drm_mode_equal(pmode, mode)) {
+				found_it = 1;
+				/* if equal delete the probed mode */
+				mode->status = pmode->status;
+				list_del(&pmode->head);
+				kfree(pmode);
+				break;
+			}
+		}
+
+		if (!found_it) {
+			list_move_tail(&pmode->head, &output->modes);
+		}
+	}
+}