videobuf-dma-contig: zero copy USERPTR V3 comments

@@ -110,6 +110,12 @@ static struct vm_operations_struct video
 	.close    = videobuf_vm_close,
 };
 
+/**
+ * videobuf_dma_contig_user_put() - reset pointer to user space buffer
+ * @mem: per-buffer private videobuf-dma-contig data
+ *
+ * This function resets the user space pointer 
+ */
 static void videobuf_dma_contig_user_put(struct videobuf_dma_contig_memory *mem)
 {
 	mem->is_userptr = 0;

@@ -117,6 +123,16 @@ static void videobuf_dma_contig_user_put
 	mem->size = 0;
 }
 
+/**
+ * videobuf_dma_contig_user_get() - setup user space memory pointer
+ * @mem: per-buffer private videobuf-dma-contig data
+ * @vb: video buffer to map
+ *
+ * This function validates and sets up a pointer to user space memory.
+ * Only physically contiguous pfn-mapped memory is accepted.
+ *
+ * Returns 0 if successful.
+ */
 static int videobuf_dma_contig_user_get(struct videobuf_dma_contig_memory *mem,
 					struct videobuf_buffer *vb)
 {