ANDROID: staging: ion: Add an in-kernel interface to request heap info.

Add an API to allow in-kernel clients to request heap ID info.

Test: make
Bug: 149961819

Change-Id: I59d26355115f100a60bcf8ade0e3afa4b89c5d0a
Signed-off-by: Hridya Valsaraju <hridya@google.com>

include/linux/ion.h

@@ -309,6 +309,21 @@ struct dma_buf *ion_alloc(size_t len, unsigned int heap_id_mask,
  */
 int ion_free(struct ion_buffer *buffer);
 
+/**
+ * ion_query_heaps_kernel - Returns information about available heaps to
+ * in-kernel clients.
+ *
+ * @hdata:             pointer to array of struct ion_heap_data.
+ * @size:             size of @hdata array.
+ *
+ * Returns the number of available heaps and populates @hdata with information
+ * regarding the same. When invoked with @size as 0, the function with return
+ * the number of available heaps without modifying @hdata. When the number of
+ * available heaps is higher than @size, @size is returned instead of the
+ * actual number of available heaps.
+ */
+
+size_t ion_query_heaps_kernel(struct ion_heap_data *hdata, size_t size);
 #else
 
 static inline int __ion_device_add_heap(struct ion_heap *heap,
@@ -380,5 +395,10 @@ static inline int ion_free(struct ion_buffer *buffer)
 	return 0;
 }
 
+static inline size_t ion_query_heaps_kernel(struct ion_heap_data *hdata,
+					 size_t size)
+{
+	return 0;
+}
 #endif /* CONFIG_ION */
 #endif /* _ION_KERNEL_H */