diff --git a/lib/ioctl_wrappers.h b/lib/ioctl_wrappers.h
index 8d8fa46d..663b3da2 100644
--- a/lib/ioctl_wrappers.h
+++ b/lib/ioctl_wrappers.h
@@ -78,10 +78,19 @@ void *gem_mmap__wc(int fd, uint32_t handle, int offset, int size, int prot);
 
 /**
  * gem_mmap:
+ * @fd: open i915 drm file descriptor
+ * @handle: gem buffer object handle
+ * @size: size of the gem buffer
+ * @prot: memory protection bits as used by mmap()
+ *
+ * This functions wraps up procedure to establish a memory mapping through the
+ * GTT.
  *
  * This is a simple convenience alias to gem_mmap__gtt()
+ *
+ * Returns: A pointer to the created memory mapping.
  */
-#define gem_mmap gem_mmap__gtt
+#define gem_mmap(fd, handle, size, prot) gem_mmap__gtt(fd, handle, size, prot)
 
 int gem_madvise(int fd, uint32_t handle, int state);