Index: uspace/drv/bus/usb/ohci/hc.c
===================================================================
--- uspace/drv/bus/usb/ohci/hc.c	(revision fc6e6071f5395884cc50a122d43341bdebe73c5d)
+++ uspace/drv/bus/usb/ohci/hc.c	(revision eb212e70f73e6c51b0393c67ea1e45940de721b4)
@@ -97,5 +97,11 @@
 	 * unless whole virtual addresses in irq is replaced
 	 * NOTE: Compiler won't remove this as ohci_regs_t members
-	 * are declared volatile. */
+	 * are declared volatile.
+	 *
+	 * Introducing CMD_MEM set of IRQ code commands broke
+	 * assumption that IRQ code does not cause page faults.
+	 * If this happens during idling (THREAD == NULL)
+	 * it causes kernel panic.
+	 */
 	registers->revision;