iscsi-target: Expose default_erl as TPG attribute

This patch exposes default_erl as a TPG attribute so that it may be
set TPG wide in demo-mode, but still allow the existing NodeACL
attribute to be overridden on a per initiator basis.

Reported-by: Arshad Hussain <arshad.hussain@calsoftinc.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
diff --git a/drivers/target/iscsi/iscsi_target_tpg.c b/drivers/target/iscsi/iscsi_target_tpg.c
index 98ccf0b..3976183 100644
--- a/drivers/target/iscsi/iscsi_target_tpg.c
+++ b/drivers/target/iscsi/iscsi_target_tpg.c
@@ -224,6 +224,7 @@
 	a->demo_mode_write_protect = TA_DEMO_MODE_WRITE_PROTECT;
 	a->prod_mode_write_protect = TA_PROD_MODE_WRITE_PROTECT;
 	a->demo_mode_discovery = TA_DEMO_MODE_DISCOVERY;
+	a->default_erl = TA_DEFAULT_ERL;
 }
 
 int iscsit_tpg_add_portal_group(struct iscsi_tiqn *tiqn, struct iscsi_portal_group *tpg)
@@ -840,3 +841,20 @@
 
 	return 0;
 }
+
+int iscsit_ta_default_erl(
+	struct iscsi_portal_group *tpg,
+	u32 default_erl)
+{
+	struct iscsi_tpg_attrib *a = &tpg->tpg_attrib;
+
+	if ((default_erl != 0) && (default_erl != 1) && (default_erl != 2)) {
+		pr_err("Illegal value for default_erl: %u\n", default_erl);
+		return -EINVAL;
+	}
+
+	a->default_erl = default_erl;
+	pr_debug("iSCSI_TPG[%hu] - DefaultERL: %u\n", tpg->tpgt, a->default_erl);
+
+	return 0;
+}