From f5ff6d6f34e2cab60722a8a2e8444436c969bfeb Mon Sep 17 00:00:00 2001
From: cinap_lenrek <cinap_lenrek@gmx.de>
Date: Fri, 22 Feb 2013 12:23:01 +0100
Subject: [PATCH] sdiahci: prevent nil pointer dereference on spurious
 interrupt status

on some controllers, we get bogus interrupt indication
for non present drives. ack the irq but ignore.
---
 sys/src/9/pc/sdiahci.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sys/src/9/pc/sdiahci.c b/sys/src/9/pc/sdiahci.c
index 8db494b42..6657785df 100644
--- a/sys/src/9/pc/sdiahci.c
+++ b/sys/src/9/pc/sdiahci.c
@@ -1201,7 +1201,7 @@ iainterrupt(Ureg *u, void *a)
 		cause &= ~m;
 		d = c->rawdrive + i;
 		ilock(d);
-		if(d->port->isr && c->hba->pi & m)
+		if(d->port != nil && d->port->isr && c->hba->pi & m)
 			updatedrive(d);
 		c->hba->isr = m;
 		iunlock(d);