net/smc: Introduce explicit check for v2 support

Previously, v2 support was derived from a very specific format of the SEID
as part of the SMC-D codebase. Make this part of the SMC-D device API, so
implementers do not need to adhere to a specific SEID format.
Signed-off-by: Stefan Raspl <raspl@linux.ibm.com>
Reviewed-and-tested-by: Jan Karcher <jaka@linux.ibm.com>
Reviewed-by: Wenjia Zhang <wenjia@linux.ibm.com>
Signed-off-by: Wenjia Zhang <wenjia@linux.ibm.com>
Reviewed-by: Tony Lu <tonylu@linux.alibaba.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/s390/net/ism_drv.c

@@ -842,6 +842,12 @@ static int smcd_move(struct smcd_dev *smcd, u64 dmb_tok, unsigned int idx,
 	return ism_move(smcd->priv, dmb_tok, idx, sf, offset, data, size);
 }
 
+static int smcd_supports_v2(void)
+{
+	return SYSTEM_EID.serial_number[0] != '0' ||
+		SYSTEM_EID.type[0] != '0';
+}
+
 static u64 smcd_get_local_gid(struct smcd_dev *smcd)
 {
 	return ism_get_local_gid(smcd->priv);
@@ -869,6 +875,7 @@ static const struct smcd_ops ism_ops = {
 	.reset_vlan_required = smcd_reset_vlan_required,
 	.signal_event = smcd_signal_ieq,
 	.move_data = smcd_move,
+	.supports_v2 = smcd_supports_v2,
 	.get_system_eid = ism_get_seid,
 	.get_local_gid = smcd_get_local_gid,
 	.get_chid = smcd_get_chid,

include/net/smc.h

@@ -67,6 +67,7 @@ struct smcd_ops {
 	int (*move_data)(struct smcd_dev *dev, u64 dmb_tok, unsigned int idx,
 			 bool sf, unsigned int offset, void *data,
 			 unsigned int size);
+	int (*supports_v2)(void);
 	u8* (*get_system_eid)(void);
 	u64 (*get_local_gid)(struct smcd_dev *dev);
 	u16 (*get_chid)(struct smcd_dev *dev);

net/smc/smc_ism.c

@@ -429,7 +429,7 @@ static void smcd_register_dev(struct ism_dev *ism)
 		u8 *system_eid = NULL;
 
 		system_eid = smcd->ops->get_system_eid();
-		if (system_eid[24] != '0' || system_eid[28] != '0') {
+		if (smcd->ops->supports_v2()) {
 			smc_ism_v2_capable = true;
 			memcpy(smc_ism_v2_system_eid, system_eid,
 			       SMC_MAX_EID_LEN);