firewire: fw-sbp2: set correct maximum payload (fixes CardBus adapters)

As far as I know, all CardBus FireWire 400 adapters have a maximum
payload of 1024 bytes which is less than the speed-dependent limit of
2048 bytes.  Fw-sbp2 has to take the host adapter's limit into account.

This apparently fixes Juju's incompatibility with my CardBus cards, a
NEC based card and a VIA based card.
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
Acked-by: Kristian Høgsberg <krh@redhat.com>

drivers/firewire/fw-sbp2.c

@@ -984,6 +984,7 @@ static int sbp2_scsi_queuecommand(struct scsi_cmnd *cmd, scsi_done_fn_t done)
 	struct fw_unit *unit = sd->unit;
 	struct fw_device *device = fw_device(unit->device.parent);
 	struct sbp2_command_orb *orb;
+	unsigned max_payload;
 
 	/*
 	 * Bidirectional commands are not yet implemented, and unknown
@@ -1017,8 +1018,10 @@ static int sbp2_scsi_queuecommand(struct scsi_cmnd *cmd, scsi_done_fn_t done)
 	 * specifies the max payload size as 2 ^ (max_payload + 2), so
 	 * if we set this to max_speed + 7, we get the right value.
 	 */
+	max_payload = min(device->max_speed + 7,
+			  device->card->max_receive - 1);
 	orb->request.misc =
-		COMMAND_ORB_MAX_PAYLOAD(device->max_speed + 7) |
+		COMMAND_ORB_MAX_PAYLOAD(max_payload) |
 		COMMAND_ORB_SPEED(device->max_speed) |
 		COMMAND_ORB_NOTIFY;
 

drivers/firewire/fw-transaction.h

@@ -231,7 +231,7 @@ struct fw_card {
 	unsigned long reset_jiffies;
 
 	unsigned long long guid;
-	int max_receive;
+	unsigned max_receive;
 	int link_speed;
 	int config_rom_generation;