firewire: Implement proper transaction cancelation.

Drivers such as fw-sbp2 had no way to properly cancel in-progress
transactions, which could leave a pending transaction or an unset
packet in the low-level queues after kfree'ing the containing
structure. fw_cancel_transaction() lets drivers cancel a submitted
transaction.

Signed-off-by: Kristian Høgsberg <krh@redhat.com>
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>

drivers/firewire/fw-card.c

@@ -474,6 +474,12 @@ dummy_send_response(struct fw_card *card, struct fw_packet *packet)
 	packet->callback(packet, card, -ENODEV);
 }
 
+static int
+dummy_cancel_packet(struct fw_card *card, struct fw_packet *packet)
+{
+	return -ENOENT;
+}
+
 static int
 dummy_enable_phys_dma(struct fw_card *card,
 		      int node_id, int generation)
@@ -487,6 +493,7 @@ static struct fw_card_driver dummy_driver = {
 	.update_phy_reg  = dummy_update_phy_reg,
 	.set_config_rom  = dummy_set_config_rom,
 	.send_request    = dummy_send_request,
+	.cancel_packet   = dummy_cancel_packet,
 	.send_response   = dummy_send_response,
 	.enable_phys_dma = dummy_enable_phys_dma,
 };