dma-buf: dma-heap: Keep track of the heap device struct

REFERENCE:
https://git.seco.com/edgehog/bsp/rockchip/linux-seco-rk/-/commit/c8bdd325554f410da577e15e7f6d5647c5dcffd5

drivers/dma-buf/dma-heap.c

@@ -30,6 +30,7 @@
  * @heap_devt		heap device node
  * @list		list head connecting to list of heaps
  * @heap_cdev		heap char device
+ * @heap_dev		heap device struct
  *
  * Represents a heap of memory from which buffers can be made.
  */
@@ -42,6 +43,7 @@ struct dma_heap {
 	struct cdev heap_cdev;
 	int minor;
 	struct kref refcount;
+	struct device *heap_dev;
 };
 
 static LIST_HEAD(heap_list);
@@ -243,10 +245,21 @@ void dma_heap_put(struct dma_heap *h)
 	mutex_unlock(&heap_list_lock);
 }
 
+/**
+ * dma_heap_get_dev() - get device struct for the heap
+ * @heap: DMA-Heap to retrieve device struct from
+ *
+ * Returns:
+ * The device struct for the heap.
+ */
+struct device *dma_heap_get_dev(struct dma_heap *heap)
+{
+	return heap->heap_dev;
+}
+
 struct dma_heap *dma_heap_add(const struct dma_heap_export_info *exp_info)
 {
 	struct dma_heap *heap, *h, *err_ret;
-	struct device *dev_ret;
 	int ret;
 
 	if (!exp_info->name || !strcmp(exp_info->name, "")) {
@@ -300,16 +313,20 @@ struct dma_heap *dma_heap_add(const struct dma_heap_export_info *exp_info)
 		goto err1;
 	}
 
-	dev_ret = device_create(dma_heap_class,
-				NULL,
-				heap->heap_devt,
-				NULL,
-				heap->name);
-	if (IS_ERR(dev_ret)) {
+	heap->heap_dev = device_create(dma_heap_class,
+				       NULL,
+				       heap->heap_devt,
+				       NULL,
+				       heap->name);
+	if (IS_ERR(heap->heap_dev)) {
 		pr_err("dma_heap: Unable to create device\n");
-		err_ret = ERR_CAST(dev_ret);
+		err_ret = ERR_CAST(heap->heap_dev);
 		goto err2;
 	}
+
+	/* Make sure it doesn't disappear on us */
+	heap->heap_dev = get_device(heap->heap_dev);
+
 	/* Add heap to the list */
 	mutex_lock(&heap_list_lock);
 	list_add(&heap->list, &heap_list);

include/linux/dma-heap.h

@@ -50,6 +50,15 @@ struct dma_heap_export_info {
  */
 void *dma_heap_get_drvdata(struct dma_heap *heap);
 
+/**
+ * dma_heap_get_dev() - get device struct for the heap
+ * @heap: DMA-Heap to retrieve device struct from
+ *
+ * Returns:
+ * The device struct for the heap.
+ */
+struct device *dma_heap_get_dev(struct dma_heap *heap);
+
 /**
  * dma_heap_add - adds a heap to dmabuf heaps
  * @exp_info:		information needed to register this heap