@@ -196,6 +196,7 @@ struct ptp_clock *ptp_clock_register(struct ptp_clock_info *info,
 {
 	struct ptp_clock *ptp;
 	int err = 0, index, major = MAJOR(ptp_devt);
+	size_t size;
 
 	if (info->n_alarm > PTP_MAX_ALARMS)
 		return ERR_PTR(-EINVAL);

@@ -238,9 +239,17 @@ struct ptp_clock *ptp_clock_register(struct ptp_clock_info *info,
 	    strcmp(parent->class->name, "ptp") == 0)
 		ptp->is_virtual_clock = true;
 
-	if (!ptp->is_virtual_clock)
+	if (!ptp->is_virtual_clock) {
 		ptp->max_vclocks = PTP_DEFAULT_MAX_VCLOCKS;
 
+		size = sizeof(int) * ptp->max_vclocks;
+		ptp->vclock_index = kzalloc(size, GFP_KERNEL);
+		if (!ptp->vclock_index) {
+			err = -ENOMEM;
+			goto no_mem_for_vclocks;
+		}
+	}
+
 	err = ptp_populate_pin_groups(ptp);
 	if (err)
 		goto no_pin_groups;

@@ -285,6 +294,8 @@ struct ptp_clock *ptp_clock_register(struct ptp_clock_info *info,
 no_pps:
 	ptp_cleanup_pin_groups(ptp);
 no_pin_groups:
+	kfree(ptp->vclock_index);
+no_mem_for_vclocks:
 	if (ptp->kworker)
 		kthread_destroy_worker(ptp->kworker);
 kworker_err:

@@ -309,6 +320,8 @@ int ptp_clock_unregister(struct ptp_clock *ptp)
 	ptp->defunct = 1;
 	wake_up_interruptible(&ptp->tsev_wq);
 
+	kfree(ptp->vclock_index);
+
 	if (ptp->kworker) {
 		kthread_cancel_delayed_work_sync(&ptp->aux_work);
 		kthread_destroy_worker(ptp->kworker);

@@ -49,6 +49,7 @@ struct ptp_clock {
 	struct kthread_delayed_work aux_work;
 	unsigned int max_vclocks;
 	unsigned int n_vclocks;
+	int *vclock_index;
 	struct mutex n_vclocks_mux; /* protect concurrent n_vclocks access */
 	bool is_virtual_clock;
 };

@@ -213,6 +213,9 @@ static ssize_t n_vclocks_store(struct device *dev,
 			if (!vclock)
 				goto out;
 
+			*(ptp->vclock_index + ptp->n_vclocks + i) =
+				vclock->clock->index;
+
 			dev_info(dev, "new virtual clock ptp%d\n",
 				 vclock->clock->index);
 		}

@@ -223,6 +226,9 @@ static ssize_t n_vclocks_store(struct device *dev,
 		i = ptp->n_vclocks - num;
 		device_for_each_child_reverse(dev, &i,
 					      unregister_vclock);
+
+		for (i = 1; i <= ptp->n_vclocks - num; i++)
+			*(ptp->vclock_index + ptp->n_vclocks - i) = -1;
 	}
 
 	if (num == 0)

@@ -256,6 +262,9 @@ static ssize_t max_vclocks_store(struct device *dev,
 				 const char *buf, size_t count)
 {
 	struct ptp_clock *ptp = dev_get_drvdata(dev);
+	unsigned int *vclock_index;
+	int err = -EINVAL;
+	size_t size;
 	u32 max;
 
 	if (kstrtou32(buf, 0, &max) || max == 0)

@@ -267,16 +276,29 @@ static ssize_t max_vclocks_store(struct device *dev,
 	if (mutex_lock_interruptible(&ptp->n_vclocks_mux))
 		return -ERESTARTSYS;
 
-	if (max < ptp->n_vclocks) {
-		mutex_unlock(&ptp->n_vclocks_mux);
-		return -EINVAL;
+	if (max < ptp->n_vclocks)
+		goto out;
+
+	size = sizeof(int) * max;
+	vclock_index = kzalloc(size, GFP_KERNEL);
+	if (!vclock_index) {
+		err = -ENOMEM;
+		goto out;
 	}
 
+	size = sizeof(int) * ptp->n_vclocks;
+	memcpy(vclock_index, ptp->vclock_index, size);
+
+	kfree(ptp->vclock_index);
+	ptp->vclock_index = vclock_index;
 	ptp->max_vclocks = max;
 
 	mutex_unlock(&ptp->n_vclocks_mux);
 
 	return count;
+out:
+	mutex_unlock(&ptp->n_vclocks_mux);
+	return err;
 }
 static DEVICE_ATTR_RW(max_vclocks);