Index: uspace/lib/usbhost/src/dma_buffer.c
===================================================================
--- uspace/lib/usbhost/src/dma_buffer.c	(revision 5dfb70c9d83e87a81d5521cc846a48fe8f84f09b)
+++ uspace/lib/usbhost/src/dma_buffer.c	(revision 86650db9894ca4d517df5dfc2e2b3c4d29a0806c)
@@ -105,4 +105,14 @@
 }
 
+/** Convert a pointer inside a buffer to physical address.
+ *
+ * @param[in] db Buffer at which virt is pointing
+ * @param[in] virt Pointer somewhere inside db
+ */
+uintptr_t dma_buffer_phys(const dma_buffer_t *db, void *virt)
+{
+	return db->phys + (virt - db->virt);
+}
+
 /**
  * @}