sparc64: ensure VIO operations are defined while being used

It's possible that VIO operations are not defined for some VIO
clients. In that case, VIO ops pointer should be checked for
NULL before being used
Signed-off-by: Jagannathan Raman <jag.raman@oracle.com>
Reviewed-by: Liam Merwick <liam.merwick@oracle.com>
Reviewed-by: Shannon Nelson <shannon.nelson@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

arch/sparc/kernel/viohs.c

@@ -223,6 +223,9 @@ static int send_rdx(struct vio_driver_state *vio)
 
 static int send_attr(struct vio_driver_state *vio)
 {
+	if (!vio->ops)
+		return -EINVAL;
+
 	return vio->ops->send_attr(vio);
 }
 
@@ -374,6 +377,9 @@ static int process_attr(struct vio_driver_state *vio, void *pkt)
 	if (!(vio->hs_state & VIO_HS_GOTVERS))
 		return handshake_failure(vio);
 
+	if (!vio->ops)
+		return 0;
+
 	err = vio->ops->handle_attr(vio, pkt);
 	if (err < 0) {
 		return handshake_failure(vio);
@@ -388,6 +394,7 @@ static int process_attr(struct vio_driver_state *vio, void *pkt)
 			vio->hs_state |= VIO_HS_SENT_DREG;
 		}
 	}
+
 	return 0;
 }
 
@@ -647,10 +654,13 @@ int vio_control_pkt_engine(struct vio_driver_state *vio, void *pkt)
 		err = process_unknown(vio, pkt);
 		break;
 	}
+
 	if (!err &&
 	    vio->hs_state != prev_state &&
-	    (vio->hs_state & VIO_HS_COMPLETE))
-		vio->ops->handshake_complete(vio);
+	    (vio->hs_state & VIO_HS_COMPLETE)) {
+		if (vio->ops)
+			vio->ops->handshake_complete(vio);
+	}
 
 	return err;
 }
@@ -805,8 +815,7 @@ int vio_driver_init(struct vio_driver_state *vio, struct vio_dev *vdev,
 		return -EINVAL;
 	}
 
-	if (!ops->send_attr ||
-	    !ops->handle_attr ||
+	if (!ops || !ops->send_attr || !ops->handle_attr ||
 	    !ops->handshake_complete)
 		return -EINVAL;