[SCSI] tcm_loop: Add multi-fabric Linux/SCSI LLD fabric module

This patch adds the TCM_Loop Linux/SCSI LLD fabric module for
accessing TCM device backstores as locally accessable SCSI LUNs in
virtual SAS, FC, and iSCSI Target ports using the generic fabric
TransportID and Target Port WWN naming handlers from TCM's
target_core_fabric_lib.c The TCM_Loop module uses the generic fabric
configfs infratructure provided by target_core_fabric_configfs.c and
adds a module dependent attribute for the creation/release of the
virtual I_T Nexus connected the TCM_Loop Target and Initiator Ports.

TCM_Loop can also be used with scsi-generic and BSG drivers so that
STGT userspace fabric modules, QEMU-KVM and other hypervisor SCSI
passthrough support can access TCM device backstore and control CDB
emulation.

For more information please see:

http://linux-iscsi.org/wiki/Tcm_loop

[jejb: fixed up checkpatch stuff]
Signed-off-by: Nicholas A. Bellinger <nab@linux-iscsi.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>

6 files changed, 1673 insertions, 0 deletions

diff --git a/drivers/target/Kconfig b/drivers/target/Kconfig
index 2fac3be..9ef2dbb 100644
--- a/drivers/target/Kconfig
+++ b/drivers/target/Kconfig
@@ -29,4 +29,6 @@ config TCM_PSCSI
 	Say Y here to enable the TCM/pSCSI subsystem plugin for non-buffered
 	passthrough access to Linux/SCSI device
 
+source "drivers/target/loopback/Kconfig"
+
 endif
diff --git a/drivers/target/Makefile b/drivers/target/Makefile
index 4f3cb78..1178bbf 100644
--- a/drivers/target/Makefile
+++ b/drivers/target/Makefile
@@ -21,3 +21,6 @@ obj-$(CONFIG_TARGET_CORE)	+= target_core_mod.o
 obj-$(CONFIG_TCM_IBLOCK)	+= target_core_iblock.o
 obj-$(CONFIG_TCM_FILEIO)	+= target_core_file.o
 obj-$(CONFIG_TCM_PSCSI)		+= target_core_pscsi.o
+
+# Fabric modules
+obj-$(CONFIG_LOOPBACK_TARGET)	+= loopback/
diff --git a/drivers/target/loopback/Kconfig b/drivers/target/loopback/Kconfig
new file mode 100644
index 0000000..57dcbc2
--- /dev/null
+++ b/drivers/target/loopback/Kconfig
@@ -0,0 +1,11 @@
+config LOOPBACK_TARGET
+	tristate "TCM Virtual SAS target and Linux/SCSI LDD fabric loopback module"
+	help
+	  Say Y here to enable the TCM Virtual SAS target and Linux/SCSI LLD
+	  fabric loopback module.
+
+config LOOPBACK_TARGET_CDB_DEBUG
+	bool "TCM loopback fabric module CDB debug code"
+	depends on LOOPBACK_TARGET
+	help
+	  Say Y here to enable the TCM loopback fabric module CDB debug code
diff --git a/drivers/target/loopback/Makefile b/drivers/target/loopback/Makefile
new file mode 100644
index 0000000..6abebdf
--- /dev/null
+++ b/drivers/target/loopback/Makefile
@@ -0,0 +1 @@
+obj-$(CONFIG_LOOPBACK_TARGET)	+= tcm_loop.o
diff --git a/drivers/target/loopback/tcm_loop.c b/drivers/target/loopback/tcm_loop.c
new file mode 100644
index 0000000..aed4e46
--- /dev/null
+++ b/drivers/target/loopback/tcm_loop.c
@@ -0,0 +1,1579 @@
+/*******************************************************************************
+ *
+ * This file contains the Linux/SCSI LLD virtual SCSI initiator driver
+ * for emulated SAS initiator ports
+ *
+ * © Copyright 2011 RisingTide Systems LLC.
+ *
+ * Licensed to the Linux Foundation under the General Public License (GPL) version 2.
+ *
+ * Author: Nicholas A. Bellinger <nab@risingtidesystems.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ ****************************************************************************/
+
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <linux/types.h>
+#include <linux/configfs.h>
+#include <scsi/scsi.h>
+#include <scsi/scsi_tcq.h>
+#include <scsi/scsi_host.h>
+#include <scsi/scsi_device.h>
+#include <scsi/scsi_cmnd.h>
+#include <scsi/libsas.h> /* For TASK_ATTR_* */
+
+#include <target/target_core_base.h>
+#include <target/target_core_transport.h>
+#include <target/target_core_fabric_ops.h>
+#include <target/target_core_fabric_configfs.h>
+#include <target/target_core_fabric_lib.h>
+#include <target/target_core_configfs.h>
+#include <target/target_core_device.h>
+#include <target/target_core_tpg.h>
+#include <target/target_core_tmr.h>
+
+#include "tcm_loop.h"
+
+#define to_tcm_loop_hba(hba)	container_of(hba, struct tcm_loop_hba, dev)
+
+/* Local pointer to allocated TCM configfs fabric module */
+static struct target_fabric_configfs *tcm_loop_fabric_configfs;
+
+static struct kmem_cache *tcm_loop_cmd_cache;
+
+static int tcm_loop_hba_no_cnt;
+
+/*
+ * Allocate a tcm_loop cmd descriptor from target_core_mod code
+ *
+ * Can be called from interrupt context in tcm_loop_queuecommand() below
+ */
+static struct se_cmd *tcm_loop_allocate_core_cmd(
+	struct tcm_loop_hba *tl_hba,
+	struct se_portal_group *se_tpg,
+	struct scsi_cmnd *sc)
+{
+	struct se_cmd *se_cmd;
+	struct se_session *se_sess;
+	struct tcm_loop_nexus *tl_nexus = tl_hba->tl_nexus;
+	struct tcm_loop_cmd *tl_cmd;
+	int sam_task_attr;
+
+	if (!tl_nexus) {
+		scmd_printk(KERN_ERR, sc, "TCM_Loop I_T Nexus"
+				" does not exist\n");
+		set_host_byte(sc, DID_ERROR);
+		return NULL;
+	}
+	se_sess = tl_nexus->se_sess;
+
+	tl_cmd = kmem_cache_zalloc(tcm_loop_cmd_cache, GFP_ATOMIC);
+	if (!tl_cmd) {
+		printk(KERN_ERR "Unable to allocate struct tcm_loop_cmd\n");
+		set_host_byte(sc, DID_ERROR);
+		return NULL;
+	}
+	se_cmd = &tl_cmd->tl_se_cmd;
+	/*
+	 * Save the pointer to struct scsi_cmnd *sc
+	 */
+	tl_cmd->sc = sc;
+	/*
+	 * Locate the SAM Task Attr from struct scsi_cmnd *
+	 */
+	if (sc->device->tagged_supported) {
+		switch (sc->tag) {
+		case HEAD_OF_QUEUE_TAG:
+			sam_task_attr = TASK_ATTR_HOQ;
+			break;
+		case ORDERED_QUEUE_TAG:
+			sam_task_attr = TASK_ATTR_ORDERED;
+			break;
+		default:
+			sam_task_attr = TASK_ATTR_SIMPLE;
+			break;
+		}
+	} else
+		sam_task_attr = TASK_ATTR_SIMPLE;
+
+	/*
+	 * Initialize struct se_cmd descriptor from target_core_mod infrastructure
+	 */
+	transport_init_se_cmd(se_cmd, se_tpg->se_tpg_tfo, se_sess,
+			scsi_bufflen(sc), sc->sc_data_direction, sam_task_attr,
+			&tl_cmd->tl_sense_buf[0]);
+
+	/*
+	 * Signal BIDI usage with T_TASK(cmd)->t_tasks_bidi
+	 */
+	if (scsi_bidi_cmnd(sc))
+		T_TASK(se_cmd)->t_tasks_bidi = 1;
+	/*
+	 * Locate the struct se_lun pointer and attach it to struct se_cmd
+	 */
+	if (transport_get_lun_for_cmd(se_cmd, NULL, tl_cmd->sc->device->lun) < 0) {
+		kmem_cache_free(tcm_loop_cmd_cache, tl_cmd);
+		set_host_byte(sc, DID_NO_CONNECT);
+		return NULL;
+	}
+
+	transport_device_setup_cmd(se_cmd);
+	return se_cmd;
+}
+
+/*
+ * Called by struct target_core_fabric_ops->new_cmd_map()
+ *
+ * Always called in process context.  A non zero return value
+ * here will signal to handle an exception based on the return code.
+ */
+static int tcm_loop_new_cmd_map(struct se_cmd *se_cmd)
+{
+	struct tcm_loop_cmd *tl_cmd = container_of(se_cmd,
+				struct tcm_loop_cmd, tl_se_cmd);
+	struct scsi_cmnd *sc = tl_cmd->sc;
+	void *mem_ptr, *mem_bidi_ptr = NULL;
+	u32 sg_no_bidi = 0;
+	int ret;
+	/*
+	 * Allocate the necessary tasks to complete the received CDB+data
+	 */
+	ret = transport_generic_allocate_tasks(se_cmd, tl_cmd->sc->cmnd);
+	if (ret == -1) {
+		/* Out of Resources */
+		return PYX_TRANSPORT_LU_COMM_FAILURE;
+	} else if (ret == -2) {
+		/*
+		 * Handle case for SAM_STAT_RESERVATION_CONFLICT
+		 */
+		if (se_cmd->se_cmd_flags & SCF_SCSI_RESERVATION_CONFLICT)
+			return PYX_TRANSPORT_RESERVATION_CONFLICT;
+		/*
+		 * Otherwise, return SAM_STAT_CHECK_CONDITION and return
+		 * sense data.
+		 */
+		return PYX_TRANSPORT_USE_SENSE_REASON;
+	}
+	/*
+	 * Setup the struct scatterlist memory from the received
+	 * struct scsi_cmnd.
+	 */
+	if (scsi_sg_count(sc)) {
+		se_cmd->se_cmd_flags |= SCF_PASSTHROUGH_SG_TO_MEM;
+		mem_ptr = (void *)scsi_sglist(sc);
+		/*
+		 * For BIDI commands, pass in the extra READ buffer
+		 * to transport_generic_map_mem_to_cmd() below..
+		 */
+		if (T_TASK(se_cmd)->t_tasks_bidi) {
+			struct scsi_data_buffer *sdb = scsi_in(sc);
+
+			mem_bidi_ptr = (void *)sdb->table.sgl;
+			sg_no_bidi = sdb->table.nents;
+		}
+	} else {
+		/*
+		 * Used for DMA_NONE
+		 */
+		mem_ptr = NULL;
+	}
+	/*
+	 * Map the SG memory into struct se_mem->page linked list using the same
+	 * physical memory at sg->page_link.
+	 */
+	ret = transport_generic_map_mem_to_cmd(se_cmd, mem_ptr,
+			scsi_sg_count(sc), mem_bidi_ptr, sg_no_bidi);
+	if (ret < 0)
+		return PYX_TRANSPORT_LU_COMM_FAILURE;
+
+	return 0;
+}
+
+/*
+ * Called from struct target_core_fabric_ops->check_stop_free()
+ */
+static void tcm_loop_check_stop_free(struct se_cmd *se_cmd)
+{
+	/*
+	 * Do not release struct se_cmd's containing a valid TMR
+	 * pointer.  These will be released directly in tcm_loop_device_reset()
+	 * with transport_generic_free_cmd().
+	 */
+	if (se_cmd->se_tmr_req)
+		return;
+	/*
+	 * Release the struct se_cmd, which will make a callback to release
+	 * struct tcm_loop_cmd * in tcm_loop_deallocate_core_cmd()
+	 */
+	transport_generic_free_cmd(se_cmd, 0, 1, 0);
+}
+
+/*
+ * Called from struct target_core_fabric_ops->release_cmd_to_pool()
+ */
+static void tcm_loop_deallocate_core_cmd(struct se_cmd *se_cmd)
+{
+	struct tcm_loop_cmd *tl_cmd = container_of(se_cmd,
+				struct tcm_loop_cmd, tl_se_cmd);
+
+	kmem_cache_free(tcm_loop_cmd_cache, tl_cmd);
+}
+
+static int tcm_loop_proc_info(struct Scsi_Host *host, char *buffer,
+				char **start, off_t offset,
+				int length, int inout)
+{
+	return sprintf(buffer, "tcm_loop_proc_info()\n");
+}
+
+static int tcm_loop_driver_probe(struct device *);
+static int tcm_loop_driver_remove(struct device *);
+
+static int pseudo_lld_bus_match(struct device *dev,
+				struct device_driver *dev_driver)
+{
+	return 1;
+}
+
+static struct bus_type tcm_loop_lld_bus = {
+	.name			= "tcm_loop_bus",
+	.match			= pseudo_lld_bus_match,
+	.probe			= tcm_loop_driver_probe,
+	.remove			= tcm_loop_driver_remove,
+};
+
+static struct device_driver tcm_loop_driverfs = {
+	.name			= "tcm_loop",
+	.bus			= &tcm_loop_lld_bus,
+};
+/*
+ * Used with root_device_register() in tcm_loop_alloc_core_bus() below
+ */
+struct device *tcm_loop_primary;
+
+/*
+ * Copied from drivers/scsi/libfc/fc_fcp.c:fc_change_queue_depth() and
+ * drivers/scsi/libiscsi.c:iscsi_change_queue_depth()
+ */
+static int tcm_loop_change_queue_depth(
+	struct scsi_device *sdev,
+	int depth,
+	int reason)
+{
+	switch (reason) {
+	case SCSI_QDEPTH_DEFAULT:
+		scsi_adjust_queue_depth(sdev, scsi_get_tag_type(sdev), depth);
+		break;
+	case SCSI_QDEPTH_QFULL:
+		scsi_track_queue_full(sdev, depth);
+		break;
+	case SCSI_QDEPTH_RAMP_UP:
+		scsi_adjust_queue_depth(sdev, scsi_get_tag_type(sdev), depth);
+		break;
+	default:
+		return -EOPNOTSUPP;
+	}
+	return sdev->queue_depth;
+}
+
+/*
+ * Main entry point from struct scsi_host_template for incoming SCSI CDB+Data
+ * from Linux/SCSI subsystem for SCSI low level device drivers (LLDs)
+ */
+static int tcm_loop_queuecommand(
+	struct Scsi_Host *sh,
+	struct scsi_cmnd *sc)
+{
+	struct se_cmd *se_cmd;
+	struct se_portal_group *se_tpg;
+	struct tcm_loop_hba *tl_hba;
+	struct tcm_loop_tpg *tl_tpg;
+
+	TL_CDB_DEBUG("tcm_loop_queuecommand() %d:%d:%d:%d got CDB: 0x%02x"
+		" scsi_buf_len: %u\n", sc->device->host->host_no,
+		sc->device->id, sc->device->channel, sc->device->lun,
+		sc->cmnd[0], scsi_bufflen(sc));
+	/*
+	 * Locate the tcm_loop_hba_t pointer
+	 */
+	tl_hba = *(struct tcm_loop_hba **)shost_priv(sc->device->host);
+	tl_tpg = &tl_hba->tl_hba_tpgs[sc->device->id];
+	se_tpg = &tl_tpg->tl_se_tpg;
+	/*
+	 * Determine the SAM Task Attribute and allocate tl_cmd and
+	 * tl_cmd->tl_se_cmd from TCM infrastructure
+	 */
+	se_cmd = tcm_loop_allocate_core_cmd(tl_hba, se_tpg, sc);
+	if (!se_cmd) {
+		sc->scsi_done(sc);
+		return 0;
+	}
+	/*
+	 * Queue up the newly allocated to be processed in TCM thread context.
+	*/
+	transport_generic_handle_cdb_map(se_cmd);
+	return 0;
+}
+
+/*
+ * Called from SCSI EH process context to issue a LUN_RESET TMR
+ * to struct scsi_device
+ */
+static int tcm_loop_device_reset(struct scsi_cmnd *sc)
+{
+	struct se_cmd *se_cmd = NULL;
+	struct se_portal_group *se_tpg;
+	struct se_session *se_sess;
+	struct tcm_loop_cmd *tl_cmd = NULL;
+	struct tcm_loop_hba *tl_hba;
+	struct tcm_loop_nexus *tl_nexus;
+	struct tcm_loop_tmr *tl_tmr = NULL;
+	struct tcm_loop_tpg *tl_tpg;
+	int ret = FAILED;
+	/*
+	 * Locate the tcm_loop_hba_t pointer
+	 */
+	tl_hba = *(struct tcm_loop_hba **)shost_priv(sc->device->host);
+	/*
+	 * Locate the tl_nexus and se_sess pointers
+	 */
+	tl_nexus = tl_hba->tl_nexus;
+	if (!tl_nexus) {
+		printk(KERN_ERR "Unable to perform device reset without"
+				" active I_T Nexus\n");
+		return FAILED;
+	}
+	se_sess = tl_nexus->se_sess;
+	/*
+	 * Locate the tl_tpg and se_tpg pointers from TargetID in sc->device->id
+	 */
+	tl_tpg = &tl_hba->tl_hba_tpgs[sc->device->id];
+	se_tpg = &tl_tpg->tl_se_tpg;
+
+	tl_cmd = kmem_cache_zalloc(tcm_loop_cmd_cache, GFP_KERNEL);
+	if (!tl_cmd) {
+		printk(KERN_ERR "Unable to allocate memory for tl_cmd\n");
+		return FAILED;
+	}
+
+	tl_tmr = kzalloc(sizeof(struct tcm_loop_tmr), GFP_KERNEL);
+	if (!tl_tmr) {
+		printk(KERN_ERR "Unable to allocate memory for tl_tmr\n");
+		goto release;
+	}
+	init_waitqueue_head(&tl_tmr->tl_tmr_wait);
+
+	se_cmd = &tl_cmd->tl_se_cmd;
+	/*
+	 * Initialize struct se_cmd descriptor from target_core_mod infrastructure
+	 */
+	transport_init_se_cmd(se_cmd, se_tpg->se_tpg_tfo, se_sess, 0,
+				DMA_NONE, TASK_ATTR_SIMPLE,
+				&tl_cmd->tl_sense_buf[0]);
+	/*
+	 * Allocate the LUN_RESET TMR
+	 */
+	se_cmd->se_tmr_req = core_tmr_alloc_req(se_cmd, (void *)tl_tmr,
+				TMR_LUN_RESET);
+	if (!se_cmd->se_tmr_req)
+		goto release;
+	/*
+	 * Locate the underlying TCM struct se_lun from sc->device->lun
+	 */
+	if (transport_get_lun_for_tmr(se_cmd, sc->device->lun) < 0)
+		goto release;
+	/*
+	 * Queue the TMR to TCM Core and sleep waiting for tcm_loop_queue_tm_rsp()
+	 * to wake us up.
+	 */
+	transport_generic_handle_tmr(se_cmd);
+	wait_event(tl_tmr->tl_tmr_wait, atomic_read(&tl_tmr->tmr_complete));
+	/*
+	 * The TMR LUN_RESET has completed, check the response status and
+	 * then release allocations.
+	 */
+	ret = (se_cmd->se_tmr_req->response == TMR_FUNCTION_COMPLETE) ?
+		SUCCESS : FAILED;
+release:
+	if (se_cmd)
+		transport_generic_free_cmd(se_cmd, 1, 1, 0);
+	else
+		kmem_cache_free(tcm_loop_cmd_cache, tl_cmd);
+	kfree(tl_tmr);
+	return ret;
+}
+
+static int tcm_loop_slave_alloc(struct scsi_device *sd)
+{
+	set_bit(QUEUE_FLAG_BIDI, &sd->request_queue->queue_flags);
+	return 0;
+}
+
+static int tcm_loop_slave_configure(struct scsi_device *sd)
+{
+	return 0;
+}
+
+static struct scsi_host_template tcm_loop_driver_template = {
+	.proc_info		= tcm_loop_proc_info,
+	.proc_name		= "tcm_loopback",
+	.name			= "TCM_Loopback",
+	.queuecommand		= tcm_loop_queuecommand,
+	.change_queue_depth	= tcm_loop_change_queue_depth,
+	.eh_device_reset_handler = tcm_loop_device_reset,
+	.can_queue		= TL_SCSI_CAN_QUEUE,
+	.this_id		= -1,
+	.sg_tablesize		= TL_SCSI_SG_TABLESIZE,
+	.cmd_per_lun		= TL_SCSI_CMD_PER_LUN,
+	.max_sectors		= TL_SCSI_MAX_SECTORS,
+	.use_clustering		= DISABLE_CLUSTERING,
+	.slave_alloc		= tcm_loop_slave_alloc,
+	.slave_configure	= tcm_loop_slave_configure,
+	.module			= THIS_MODULE,
+};
+
+static int tcm_loop_driver_probe(struct device *dev)
+{
+	struct tcm_loop_hba *tl_hba;
+	struct Scsi_Host *sh;
+	int error;
+
+	tl_hba = to_tcm_loop_hba(dev);
+
+	sh = scsi_host_alloc(&tcm_loop_driver_template,
+			sizeof(struct tcm_loop_hba));
+	if (!sh) {
+		printk(KERN_ERR "Unable to allocate struct scsi_host\n");
+		return -ENODEV;
+	}
+	tl_hba->sh = sh;
+
+	/*
+	 * Assign the struct tcm_loop_hba pointer to struct Scsi_Host->hostdata
+	 */
+	*((struct tcm_loop_hba **)sh->hostdata) = tl_hba;
+	/*
+	 * Setup single ID, Channel and LUN for now..
+	 */
+	sh->max_id = 2;
+	sh->max_lun = 0;
+	sh->max_channel = 0;
+	sh->max_cmd_len = TL_SCSI_MAX_CMD_LEN;
+
+	error = scsi_add_host(sh, &tl_hba->dev);
+	if (error) {
+		printk(KERN_ERR "%s: scsi_add_host failed\n", __func__);
+		scsi_host_put(sh);
+		return -ENODEV;
+	}
+	return 0;
+}
+
+static int tcm_loop_driver_remove(struct device *dev)
+{
+	struct tcm_loop_hba *tl_hba;
+	struct Scsi_Host *sh;
+
+	tl_hba = to_tcm_loop_hba(dev);
+	sh = tl_hba->sh;
+
+	scsi_remove_host(sh);
+	scsi_host_put(sh);
+	return 0;
+}
+
+static void tcm_loop_release_adapter(struct device *dev)
+{
+	struct tcm_loop_hba *tl_hba = to_tcm_loop_hba(dev);
+
+	kfree(tl_hba);
+}
+
+/*
+ * Called from tcm_loop_make_scsi_hba() in tcm_loop_configfs.c
+ */
+static int tcm_loop_setup_hba_bus(struct tcm_loop_hba *tl_hba, int tcm_loop_host_id)
+{
+	int ret;
+
+	tl_hba->dev.bus = &tcm_loop_lld_bus;
+	tl_hba->dev.parent = tcm_loop_primary;
+	tl_hba->dev.release = &tcm_loop_release_adapter;
+	dev_set_name(&tl_hba->dev, "tcm_loop_adapter_%d", tcm_loop_host_id);
+
+	ret = device_register(&tl_hba->dev);
+	if (ret) {
+		printk(KERN_ERR "device_register() failed for"
+				" tl_hba->dev: %d\n", ret);
+		return -ENODEV;
+	}
+
+	return 0;
+}
+
+/*
+ * Called from tcm_loop_fabric_init() in tcl_loop_fabric.c to load the emulated
+ * tcm_loop SCSI bus.
+ */
+static int tcm_loop_alloc_core_bus(void)
+{
+	int ret;
+
+	tcm_loop_primary = root_device_register("tcm_loop_0");
+	if (IS_ERR(tcm_loop_primary)) {
+		printk(KERN_ERR "Unable to allocate tcm_loop_primary\n");
+		return PTR_ERR(tcm_loop_primary);
+	}
+
+	ret = bus_register(&tcm_loop_lld_bus);
+	if (ret) {
+		printk(KERN_ERR "bus_register() failed for tcm_loop_lld_bus\n");
+		goto dev_unreg;
+	}
+
+	ret = driver_register(&tcm_loop_driverfs);
+	if (ret) {
+		printk(KERN_ERR "driver_register() failed for"
+				"tcm_loop_driverfs\n");
+		goto bus_unreg;
+	}
+
+	printk(KERN_INFO "Initialized TCM Loop Core Bus\n");
+	return ret;
+
+bus_unreg:
+	bus_unregister(&tcm_loop_lld_bus);
+dev_unreg:
+	root_device_unregister(tcm_loop_primary);
+	return ret;
+}
+
+static void tcm_loop_release_core_bus(void)
+{
+	driver_unregister(&tcm_loop_driverfs);
+	bus_unregister(&tcm_loop_lld_bus);
+	root_device_unregister(tcm_loop_primary);
+
+	printk(KERN_INFO "Releasing TCM Loop Core BUS\n");
+}
+
+static char *tcm_loop_get_fabric_name(void)
+{
+	return "loopback";
+}
+
+static u8 tcm_loop_get_fabric_proto_ident(struct se_portal_group *se_tpg)
+{
+	struct tcm_loop_tpg *tl_tpg =
+			(struct tcm_loop_tpg *)se_tpg->se_tpg_fabric_ptr;
+	struct tcm_loop_hba *tl_hba = tl_tpg->tl_hba;
+	/*
+	 * tl_proto_id is set at tcm_loop_configfs.c:tcm_loop_make_scsi_hba()
+	 * time based on the protocol dependent prefix of the passed configfs group.
+	 *
+	 * Based upon tl_proto_id, TCM_Loop emulates the requested fabric
+	 * ProtocolID using target_core_fabric_lib.c symbols.
+	 */
+	switch (tl_hba->tl_proto_id) {
+	case SCSI_PROTOCOL_SAS:
+		return sas_get_fabric_proto_ident(se_tpg);
+	case SCSI_PROTOCOL_FCP:
+		return fc_get_fabric_proto_ident(se_tpg);
+	case SCSI_PROTOCOL_ISCSI:
+		return iscsi_get_fabric_proto_ident(se_tpg);
+	default:
+		printk(KERN_ERR "Unknown tl_proto_id: 0x%02x, using"
+			" SAS emulation\n", tl_hba->tl_proto_id);
+		break;
+	}
+
+	return sas_get_fabric_proto_ident(se_tpg);
+}
+
+static char *tcm_loop_get_endpoint_wwn(struct se_portal_group *se_tpg)
+{
+	struct tcm_loop_tpg *tl_tpg =
+		(struct tcm_loop_tpg *)se_tpg->se_tpg_fabric_ptr;
+	/*
+	 * Return the passed NAA identifier for the SAS Target Port
+	 */
+	return &tl_tpg->tl_hba->tl_wwn_address[0];
+}
+
+static u16 tcm_loop_get_tag(struct se_portal_group *se_tpg)
+{
+	struct tcm_loop_tpg *tl_tpg =
+		(struct tcm_loop_tpg *)se_tpg->se_tpg_fabric_ptr;
+	/*
+	 * This Tag is used when forming SCSI Name identifier in EVPD=1 0x83
+	 * to represent the SCSI Target Port.
+	 */
+	return tl_tpg->tl_tpgt;
+}
+
+static u32 tcm_loop_get_default_depth(struct se_portal_group *se_tpg)
+{
+	return 1;
+}
+
+static u32 tcm_loop_get_pr_transport_id(
+	struct se_portal_group *se_tpg,
+	struct se_node_acl *se_nacl,
+	struct t10_pr_registration *pr_reg,
+	int *format_code,
+	unsigned char *buf)
+{
+	struct tcm_loop_tpg *tl_tpg =
+			(struct tcm_loop_tpg *)se_tpg->se_tpg_fabric_ptr;
+	struct tcm_loop_hba *tl_hba = tl_tpg->tl_hba;
+
+	switch (tl_hba->tl_proto_id) {
+	case SCSI_PROTOCOL_SAS:
+		return sas_get_pr_transport_id(se_tpg, se_nacl, pr_reg,
+					format_code, buf);
+	case SCSI_PROTOCOL_FCP:
+		return fc_get_pr_transport_id(se_tpg, se_nacl, pr_reg,
+					format_code, buf);
+	case SCSI_PROTOCOL_ISCSI:
+		return iscsi_get_pr_transport_id(se_tpg, se_nacl, pr_reg,
+					format_code, buf);
+	default:
+		printk(KERN_ERR "Unknown tl_proto_id: 0x%02x, using"
+			" SAS emulation\n", tl_hba->tl_proto_id);
+		break;
+	}
+
+	return sas_get_pr_transport_id(se_tpg, se_nacl, pr_reg,
+			format_code, buf);
+}
+
+static u32 tcm_loop_get_pr_transport_id_len(
+	struct se_portal_group *se_tpg,
+	struct se_node_acl *se_nacl,
+	struct t10_pr_registration *pr_reg,
+	int *format_code)
+{
+	struct tcm_loop_tpg *tl_tpg =
+			(struct tcm_loop_tpg *)se_tpg->se_tpg_fabric_ptr;
+	struct tcm_loop_hba *tl_hba = tl_tpg->tl_hba;
+
+	switch (tl_hba->tl_proto_id) {
+	case SCSI_PROTOCOL_SAS:
+		return sas_get_pr_transport_id_len(se_tpg, se_nacl, pr_reg,
+					format_code);
+	case SCSI_PROTOCOL_FCP:
+		return fc_get_pr_transport_id_len(se_tpg, se_nacl, pr_reg,
+					format_code);
+	case SCSI_PROTOCOL_ISCSI:
+		return iscsi_get_pr_transport_id_len(se_tpg, se_nacl, pr_reg,
+					format_code);
+	default:
+		printk(KERN_ERR "Unknown tl_proto_id: 0x%02x, using"
+			" SAS emulation\n", tl_hba->tl_proto_id);
+		break;
+	}
+
+	return sas_get_pr_transport_id_len(se_tpg, se_nacl, pr_reg,
+			format_code);
+}
+
+/*
+ * Used for handling SCSI fabric dependent TransportIDs in SPC-3 and above
+ * Persistent Reservation SPEC_I_PT=1 and PROUT REGISTER_AND_MOVE operations.
+ */
+static char *tcm_loop_parse_pr_out_transport_id(
+	struct se_portal_group *se_tpg,
+	const char *buf,
+	u32 *out_tid_len,
+	char **port_nexus_ptr)
+{
+	struct tcm_loop_tpg *tl_tpg =
+			(struct tcm_loop_tpg *)se_tpg->se_tpg_fabric_ptr;
+	struct tcm_loop_hba *tl_hba = tl_tpg->tl_hba;
+
+	switch (tl_hba->tl_proto_id) {
+	case SCSI_PROTOCOL_SAS:
+		return sas_parse_pr_out_transport_id(se_tpg, buf, out_tid_len,
+					port_nexus_ptr);
+	case SCSI_PROTOCOL_FCP:
+		return fc_parse_pr_out_transport_id(se_tpg, buf, out_tid_len,
+					port_nexus_ptr);
+	case SCSI_PROTOCOL_ISCSI:
+		return iscsi_parse_pr_out_transport_id(se_tpg, buf, out_tid_len,
+					port_nexus_ptr);
+	default:
+		printk(KERN_ERR "Unknown tl_proto_id: 0x%02x, using"
+			" SAS emulation\n", tl_hba->tl_proto_id);
+		break;
+	}
+
+	return sas_parse_pr_out_transport_id(se_tpg, buf, out_tid_len,
+			port_nexus_ptr);
+}
+
+/*
+ * Returning (1) here allows for target_core_mod struct se_node_acl to be generated
+ * based upon the incoming fabric dependent SCSI Initiator Port
+ */
+static int tcm_loop_check_demo_mode(struct se_portal_group *se_tpg)
+{
+	return 1;
+}
+
+static int tcm_loop_check_demo_mode_cache(struct se_portal_group *se_tpg)
+{
+	return 0;
+}
+
+/*
+ * Allow I_T Nexus full READ-WRITE access without explict Initiator Node ACLs for
+ * local virtual Linux/SCSI LLD passthrough into VM hypervisor guest
+ */
+static int tcm_loop_check_demo_mode_write_protect(struct se_portal_group *se_tpg)
+{
+	return 0;
+}
+
+/*
+ * Because TCM_Loop does not use explict ACLs and MappedLUNs, this will
+ * never be called for TCM_Loop by target_core_fabric_configfs.c code.
+ * It has been added here as a nop for target_fabric_tf_ops_check()
+ */
+static int tcm_loop_check_prod_mode_write_protect(struct se_portal_group *se_tpg)
+{
+	return 0;
+}
+
+static struct se_node_acl *tcm_loop_tpg_alloc_fabric_acl(
+	struct se_portal_group *se_tpg)
+{
+	struct tcm_loop_nacl *tl_nacl;
+
+	tl_nacl = kzalloc(sizeof(struct tcm_loop_nacl), GFP_KERNEL);
+	if (!tl_nacl) {
+		printk(KERN_ERR "Unable to allocate struct tcm_loop_nacl\n");
+		return NULL;
+	}
+
+	return &tl_nacl->se_node_acl;
+}
+
+static void tcm_loop_tpg_release_fabric_acl(
+	struct se_portal_group *se_tpg,
+	struct se_node_acl *se_nacl)
+{
+	struct tcm_loop_nacl *tl_nacl = container_of(se_nacl,
+				struct tcm_loop_nacl, se_node_acl);
+
+	kfree(tl_nacl);
+}
+
+static u32 tcm_loop_get_inst_index(struct se_portal_group *se_tpg)
+{
+	return 1;
+}
+
+static void tcm_loop_new_cmd_failure(struct se_cmd *se_cmd)
+{
+	/*
+	 * Since TCM_loop is already passing struct scatterlist data from
+	 * struct scsi_cmnd, no more Linux/SCSI failure dependent state need
+	 * to be handled here.
+	 */
+	return;
+}
+
+static int tcm_loop_is_state_remove(struct se_cmd *se_cmd)
+{
+	/*
+	 * Assume struct scsi_cmnd is not in remove state..
+	 */
+	return 0;
+}
+
+static int tcm_loop_sess_logged_in(struct se_session *se_sess)
+{
+	/*
+	 * Assume that TL Nexus is always active
+	 */
+	return 1;
+}
+
+static u32 tcm_loop_sess_get_index(struct se_session *se_sess)
+{
+	return 1;
+}
+
+static void tcm_loop_set_default_node_attributes(struct se_node_acl *se_acl)
+{
+	return;
+}
+
+static u32 tcm_loop_get_task_tag(struct se_cmd *se_cmd)
+{
+	return 1;
+}
+
+static int tcm_loop_get_cmd_state(struct se_cmd *se_cmd)
+{
+	struct tcm_loop_cmd *tl_cmd = container_of(se_cmd,
+			struct tcm_loop_cmd, tl_se_cmd);
+
+	return tl_cmd->sc_cmd_state;
+}
+
+static int tcm_loop_shutdown_session(struct se_session *se_sess)
+{
+	return 0;
+}
+
+static void tcm_loop_close_session(struct se_session *se_sess)
+{
+	return;
+};
+
+static void tcm_loop_stop_session(
+	struct se_session *se_sess,
+	int sess_sleep,
+	int conn_sleep)
+{
+	return;
+}
+
+static void tcm_loop_fall_back_to_erl0(struct se_session *se_sess)
+{
+	return;
+}
+
+static int tcm_loop_write_pending(struct se_cmd *se_cmd)
+{
+	/*
+	 * Since Linux/SCSI has already sent down a struct scsi_cmnd
+	 * sc->sc_data_direction of DMA_TO_DEVICE with struct scatterlist array
+	 * memory, and memory has already been mapped to struct se_cmd->t_mem_list
+	 * format with transport_generic_map_mem_to_cmd().
+	 *
+	 * We now tell TCM to add this WRITE CDB directly into the TCM storage
+	 * object execution queue.
+	 */
+	transport_generic_process_write(se_cmd);
+	return 0;
+}
+
+static int tcm_loop_write_pending_status(struct se_cmd *se_cmd)
+{
+	return 0;
+}
+
+static int tcm_loop_queue_data_in(struct se_cmd *se_cmd)
+{
+	struct tcm_loop_cmd *tl_cmd = container_of(se_cmd,
+				struct tcm_loop_cmd, tl_se_cmd);
+	struct scsi_cmnd *sc = tl_cmd->sc;
+
+	TL_CDB_DEBUG("tcm_loop_queue_data_in() called for scsi_cmnd: %p"
+		     " cdb: 0x%02x\n", sc, sc->cmnd[0]);
+
+	sc->result = SAM_STAT_GOOD;
+	set_host_byte(sc, DID_OK);
+	sc->scsi_done(sc);
+	return 0;
+}
+
+static int tcm_loop_queue_status(struct se_cmd *se_cmd)
+{
+	struct tcm_loop_cmd *tl_cmd = container_of(se_cmd,
+				struct tcm_loop_cmd, tl_se_cmd);
+	struct scsi_cmnd *sc = tl_cmd->sc;
+
+	TL_CDB_DEBUG("tcm_loop_queue_status() called for scsi_cmnd: %p"
+			" cdb: 0x%02x\n", sc, sc->cmnd[0]);
+
+	if (se_cmd->sense_buffer &&
+	   ((se_cmd->se_cmd_flags & SCF_TRANSPORT_TASK_SENSE) ||
+	    (se_cmd->se_cmd_flags & SCF_EMULATED_TASK_SENSE))) {
+
+		memcpy((void *)sc->sense_buffer, (void *)se_cmd->sense_buffer,
+				SCSI_SENSE_BUFFERSIZE);
+		sc->result = SAM_STAT_CHECK_CONDITION;
+		set_driver_byte(sc, DRIVER_SENSE);
+	} else
+		sc->result = se_cmd->scsi_status;
+
+	set_host_byte(sc, DID_OK);
+	sc->scsi_done(sc);
+	return 0;
+}
+
+static int tcm_loop_queue_tm_rsp(struct se_cmd *se_cmd)
+{
+	struct se_tmr_req *se_tmr = se_cmd->se_tmr_req;
+	struct tcm_loop_tmr *tl_tmr = se_tmr->fabric_tmr_ptr;
+	/*
+	 * The SCSI EH thread will be sleeping on se_tmr->tl_tmr_wait, go ahead
+	 * and wake up the wait_queue_head_t in tcm_loop_device_reset()
+	 */
+	atomic_set(&tl_tmr->tmr_complete, 1);
+	wake_up(&tl_tmr->tl_tmr_wait);
+	return 0;
+}
+
+static u16 tcm_loop_set_fabric_sense_len(struct se_cmd *se_cmd, u32 sense_length)
+{
+	return 0;
+}
+
+static u16 tcm_loop_get_fabric_sense_len(void)
+{
+	return 0;
+}
+
+static u64 tcm_loop_pack_lun(unsigned int lun)
+{
+	u64 result;
+
+	/* LSB of lun into byte 1 big-endian */
+	result = ((lun & 0xff) << 8);
+	/* use flat space addressing method */
+	result |= 0x40 | ((lun >> 8) & 0x3f);
+
+	return cpu_to_le64(result);
+}
+
+static char *tcm_loop_dump_proto_id(struct tcm_loop_hba *tl_hba)
+{
+	switch (tl_hba->tl_proto_id) {
+	case SCSI_PROTOCOL_SAS:
+		return "SAS";
+	case SCSI_PROTOCOL_FCP:
+		return "FCP";
+	case SCSI_PROTOCOL_ISCSI:
+		return "iSCSI";
+	default:
+		break;
+	}
+
+	return "Unknown";
+}
+
+/* Start items for tcm_loop_port_cit */
+
+static int tcm_loop_port_link(
+	struct se_portal_group *se_tpg,
+	struct se_lun *lun)
+{
+	struct tcm_loop_tpg *tl_tpg = container_of(se_tpg,
+				struct tcm_loop_tpg, tl_se_tpg);
+	struct tcm_loop_hba *tl_hba = tl_tpg->tl_hba;
+
+	atomic_inc(&tl_tpg->tl_tpg_port_count);
+	smp_mb__after_atomic_inc();
+	/*
+	 * Add Linux/SCSI struct scsi_device by HCTL
+	 */
+	scsi_add_device(tl_hba->sh, 0, tl_tpg->tl_tpgt, lun->unpacked_lun);
+
+	printk(KERN_INFO "TCM_Loop_ConfigFS: Port Link Successful\n");
+	return 0;
+}
+
+static void tcm_loop_port_unlink(
+	struct se_portal_group *se_tpg,
+	struct se_lun *se_lun)
+{
+	struct scsi_device *sd;
+	struct tcm_loop_hba *tl_hba;
+	struct tcm_loop_tpg *tl_tpg;
+
+	tl_tpg = container_of(se_tpg, struct tcm_loop_tpg, tl_se_tpg);
+	tl_hba = tl_tpg->tl_hba;
+
+	sd = scsi_device_lookup(tl_hba->sh, 0, tl_tpg->tl_tpgt,
+				se_lun->unpacked_lun);
+	if (!sd) {
+		printk(KERN_ERR "Unable to locate struct scsi_device for %d:%d:"
+			"%d\n", 0, tl_tpg->tl_tpgt, se_lun->unpacked_lun);
+		return;
+	}
+	/*
+	 * Remove Linux/SCSI struct scsi_device by HCTL
+	 */
+	scsi_remove_device(sd);
+	scsi_device_put(sd);
+
+	atomic_dec(&tl_tpg->tl_tpg_port_count);
+	smp_mb__after_atomic_dec();
+
+	printk(KERN_INFO "TCM_Loop_ConfigFS: Port Unlink Successful\n");
+}
+
+/* End items for tcm_loop_port_cit */
+
+/* Start items for tcm_loop_nexus_cit */
+
+static int tcm_loop_make_nexus(
+	struct tcm_loop_tpg *tl_tpg,
+	const char *name)
+{
+	struct se_portal_group *se_tpg;
+	struct tcm_loop_hba *tl_hba = tl_tpg->tl_hba;
+	struct tcm_loop_nexus *tl_nexus;
+
+	if (tl_tpg->tl_hba->tl_nexus) {
+		printk(KERN_INFO "tl_tpg->tl_hba->tl_nexus already exists\n");
+		return -EEXIST;
+	}
+	se_tpg = &tl_tpg->tl_se_tpg;
+
+	tl_nexus = kzalloc(sizeof(struct tcm_loop_nexus), GFP_KERNEL);
+	if (!tl_nexus) {
+		printk(KERN_ERR "Unable to allocate struct tcm_loop_nexus\n");
+		return -ENOMEM;
+	}
+	/*
+	 * Initialize the struct se_session pointer
+	 */
+	tl_nexus->se_sess = transport_init_session();
+	if (!tl_nexus->se_sess)
+		goto out;
+	/*
+	 * Since we are running in 'demo mode' this call with generate a
+	 * struct se_node_acl for the tcm_loop struct se_portal_group with the SCSI
+	 * Initiator port name of the passed configfs group 'name'.
+	 */
+	tl_nexus->se_sess->se_node_acl = core_tpg_check_initiator_node_acl(
+				se_tpg, (unsigned char *)name);
+	if (!tl_nexus->se_sess->se_node_acl) {
+		transport_free_session(tl_nexus->se_sess);
+		goto out;
+	}
+	/*
+	 * Now, register the SAS I_T Nexus as active with the call to
+	 * transport_register_session()
+	 */
+	__transport_register_session(se_tpg, tl_nexus->se_sess->se_node_acl,
+			tl_nexus->se_sess, (void *)tl_nexus);
+	tl_tpg->tl_hba->tl_nexus = tl_nexus;
+	printk(KERN_INFO "TCM_Loop_ConfigFS: Established I_T Nexus to emulated"
+		" %s Initiator Port: %s\n", tcm_loop_dump_proto_id(tl_hba),
+		name);
+	return 0;
+
+out:
+	kfree(tl_nexus);
+	return -ENOMEM;
+}
+
+static int tcm_loop_drop_nexus(
+	struct tcm_loop_tpg *tpg)
+{
+	struct se_session *se_sess;
+	struct tcm_loop_nexus *tl_nexus;
+	struct tcm_loop_hba *tl_hba = tpg->tl_hba;
+
+	tl_nexus = tpg->tl_hba->tl_nexus;
+	if (!tl_nexus)
+		return -ENODEV;
+
+	se_sess = tl_nexus->se_sess;
+	if (!se_sess)
+		return -ENODEV;
+
+	if (atomic_read(&tpg->tl_tpg_port_count)) {
+		printk(KERN_ERR "Unable to remove TCM_Loop I_T Nexus with"
+			" active TPG port count: %d\n",
+			atomic_read(&tpg->tl_tpg_port_count));
+		return -EPERM;
+	}
+
+	printk(KERN_INFO "TCM_Loop_ConfigFS: Removing I_T Nexus to emulated"
+		" %s Initiator Port: %s\n", tcm_loop_dump_proto_id(tl_hba),
+		tl_nexus->se_sess->se_node_acl->initiatorname);
+	/*
+	 * Release the SCSI I_T Nexus to the emulated SAS Target Port
+	 */
+	transport_deregister_session(tl_nexus->se_sess);
+	tpg->tl_hba->tl_nexus = NULL;
+	kfree(tl_nexus);
+	return 0;
+}
+
+/* End items for tcm_loop_nexus_cit */
+
+static ssize_t tcm_loop_tpg_show_nexus(
+	struct se_portal_group *se_tpg,
+	char *page)
+{
+	struct tcm_loop_tpg *tl_tpg = container_of(se_tpg,
+			struct tcm_loop_tpg, tl_se_tpg);
+	struct tcm_loop_nexus *tl_nexus;
+	ssize_t ret;
+
+	tl_nexus = tl_tpg->tl_hba->tl_nexus;
+	if (!tl_nexus)
+		return -ENODEV;
+
+	ret = snprintf(page, PAGE_SIZE, "%s\n",
+		tl_nexus->se_sess->se_node_acl->initiatorname);
+
+	return ret;
+}
+
+static ssize_t tcm_loop_tpg_store_nexus(
+	struct se_portal_group *se_tpg,
+	const char *page,
+	size_t count)
+{
+	struct tcm_loop_tpg *tl_tpg = container_of(se_tpg,
+			struct tcm_loop_tpg, tl_se_tpg);
+	struct tcm_loop_hba *tl_hba = tl_tpg->tl_hba;
+	unsigned char i_port[TL_WWN_ADDR_LEN], *ptr, *port_ptr;
+	int ret;
+	/*
+	 * Shutdown the active I_T nexus if 'NULL' is passed..
+	 */
+	if (!strncmp(page, "NULL", 4)) {
+		ret = tcm_loop_drop_nexus(tl_tpg);
+		return (!ret) ? count : ret;
+	}
+	/*
+	 * Otherwise make sure the passed virtual Initiator port WWN matches
+	 * the fabric protocol_id set in tcm_loop_make_scsi_hba(), and call
+	 * tcm_loop_make_nexus()
+	 */
+	if (strlen(page) > TL_WWN_ADDR_LEN) {
+		printk(KERN_ERR "Emulated NAA Sas Address: %s, exceeds"
+				" max: %d\n", page, TL_WWN_ADDR_LEN);
+		return -EINVAL;
+	}
+	snprintf(&i_port[0], TL_WWN_ADDR_LEN, "%s", page);
+
+	ptr = strstr(i_port, "naa.");
+	if (ptr) {
+		if (tl_hba->tl_proto_id != SCSI_PROTOCOL_SAS) {
+			printk(KERN_ERR "Passed SAS Initiator Port %s does not"
+				" match target port protoid: %s\n", i_port,
+				tcm_loop_dump_proto_id(tl_hba));
+			return -EINVAL;
+		}
+		port_ptr = &i_port[0];
+		goto check_newline;
+	}
+	ptr = strstr(i_port, "fc.");
+	if (ptr) {
+		if (tl_hba->tl_proto_id != SCSI_PROTOCOL_FCP) {
+			printk(KERN_ERR "Passed FCP Initiator Port %s does not"
+				" match target port protoid: %s\n", i_port,
+				tcm_loop_dump_proto_id(tl_hba));
+			return -EINVAL;
+		}
+		port_ptr = &i_port[3]; /* Skip over "fc." */
+		goto check_newline;
+	}
+	ptr = strstr(i_port, "iqn.");
+	if (ptr) {
+		if (tl_hba->tl_proto_id != SCSI_PROTOCOL_ISCSI) {
+			printk(KERN_ERR "Passed iSCSI Initiator Port %s does not"
+				" match target port protoid: %s\n", i_port,
+				tcm_loop_dump_proto_id(tl_hba));
+			return -EINVAL;
+		}
+		port_ptr = &i_port[0];
+		goto check_newline;
+	}
+	printk(KERN_ERR "Unable to locate prefix for emulated Initiator Port:"
+			" %s\n", i_port);
+	return -EINVAL;
+	/*
+	 * Clear any trailing newline for the NAA WWN
+	 */
+check_newline:
+	if (i_port[strlen(i_port)-1] == '\n')
+		i_port[strlen(i_port)-1] = '\0';
+
+	ret = tcm_loop_make_nexus(tl_tpg, port_ptr);
+	if (ret < 0)
+		return ret;
+
+	return count;
+}
+
+TF_TPG_BASE_ATTR(tcm_loop, nexus, S_IRUGO | S_IWUSR);
+
+static struct configfs_attribute *tcm_loop_tpg_attrs[] = {
+	&tcm_loop_tpg_nexus.attr,
+	NULL,
+};
+
+/* Start items for tcm_loop_naa_cit */
+
+struct se_portal_group *tcm_loop_make_naa_tpg(
+	struct se_wwn *wwn,
+	struct config_group *group,
+	const char *name)
+{
+	struct tcm_loop_hba *tl_hba = container_of(wwn,
+			struct tcm_loop_hba, tl_hba_wwn);
+	struct tcm_loop_tpg *tl_tpg;
+	char *tpgt_str, *end_ptr;
+	int ret;
+	unsigned short int tpgt;
+
+	tpgt_str = strstr(name, "tpgt_");
+	if (!tpgt_str) {
+		printk(KERN_ERR "Unable to locate \"tpgt_#\" directory"
+				" group\n");
+		return ERR_PTR(-EINVAL);
+	}
+	tpgt_str += 5; /* Skip ahead of "tpgt_" */
+	tpgt = (unsigned short int) simple_strtoul(tpgt_str, &end_ptr, 0);
+
+	if (tpgt > TL_TPGS_PER_HBA) {
+		printk(KERN_ERR "Passed tpgt: %hu exceeds TL_TPGS_PER_HBA:"
+				" %u\n", tpgt, TL_TPGS_PER_HBA);
+		return ERR_PTR(-EINVAL);
+	}
+	tl_tpg = &tl_hba->tl_hba_tpgs[tpgt];
+	tl_tpg->tl_hba = tl_hba;
+	tl_tpg->tl_tpgt = tpgt;
+	/*
+	 * Register the tl_tpg as a emulated SAS TCM Target Endpoint
+	 */
+	ret = core_tpg_register(&tcm_loop_fabric_configfs->tf_ops,
+			wwn, &tl_tpg->tl_se_tpg, (void *)tl_tpg,
+			TRANSPORT_TPG_TYPE_NORMAL);
+	if (ret < 0)
+		return ERR_PTR(-ENOMEM);
+
+	printk(KERN_INFO "TCM_Loop_ConfigFS: Allocated Emulated %s"
+		" Target Port %s,t,0x%04x\n", tcm_loop_dump_proto_id(tl_hba),
+		config_item_name(&wwn->wwn_group.cg_item), tpgt);
+
+	return &tl_tpg->tl_se_tpg;
+}
+
+void tcm_loop_drop_naa_tpg(
+	struct se_portal_group *se_tpg)
+{
+	struct se_wwn *wwn = se_tpg->se_tpg_wwn;
+	struct tcm_loop_tpg *tl_tpg = container_of(se_tpg,
+				struct tcm_loop_tpg, tl_se_tpg);
+	struct tcm_loop_hba *tl_hba;
+	unsigned short tpgt;
+
+	tl_hba = tl_tpg->tl_hba;
+	tpgt = tl_tpg->tl_tpgt;
+	/*
+	 * Release the I_T Nexus for the Virtual SAS link if present
+	 */
+	tcm_loop_drop_nexus(tl_tpg);
+	/*
+	 * Deregister the tl_tpg as a emulated SAS TCM Target Endpoint
+	 */
+	core_tpg_deregister(se_tpg);
+
+	printk(KERN_INFO "TCM_Loop_ConfigFS: Deallocated Emulated %s"
+		" Target Port %s,t,0x%04x\n", tcm_loop_dump_proto_id(tl_hba),
+		config_item_name(&wwn->wwn_group.cg_item), tpgt);
+}
+
+/* End items for tcm_loop_naa_cit */
+
+/* Start items for tcm_loop_cit */
+
+struct se_wwn *tcm_loop_make_scsi_hba(
+	struct target_fabric_configfs *tf,
+	struct config_group *group,
+	const char *name)
+{
+	struct tcm_loop_hba *tl_hba;
+	struct Scsi_Host *sh;
+	char *ptr;
+	int ret, off = 0;
+
+	tl_hba = kzalloc(sizeof(struct tcm_loop_hba), GFP_KERNEL);
+	if (!tl_hba) {
+		printk(KERN_ERR "Unable to allocate struct tcm_loop_hba\n");
+		return ERR_PTR(-ENOMEM);
+	}
+	/*
+	 * Determine the emulated Protocol Identifier and Target Port Name
+	 * based on the incoming configfs directory name.
+	 */
+	ptr = strstr(name, "naa.");
+	if (ptr) {
+		tl_hba->tl_proto_id = SCSI_PROTOCOL_SAS;
+		goto check_len;
+	}
+	ptr = strstr(name, "fc.");
+	if (ptr) {
+		tl_hba->tl_proto_id = SCSI_PROTOCOL_FCP;
+		off = 3; /* Skip over "fc." */
+		goto check_len;
+	}
+	ptr = strstr(name, "iqn.");
+	if (ptr) {
+		tl_hba->tl_proto_id = SCSI_PROTOCOL_ISCSI;
+		goto check_len;
+	}
+
+	printk(KERN_ERR "Unable to locate prefix for emulated Target Port:"
+			" %s\n", name);
+	return ERR_PTR(-EINVAL);
+
+check_len:
+	if (strlen(name) > TL_WWN_ADDR_LEN) {
+		printk(KERN_ERR "Emulated NAA %s Address: %s, exceeds"
+			" max: %d\n", name, tcm_loop_dump_proto_id(tl_hba),
+			TL_WWN_ADDR_LEN);
+		kfree(tl_hba);
+		return ERR_PTR(-EINVAL);
+	}
+	snprintf(&tl_hba->tl_wwn_address[0], TL_WWN_ADDR_LEN, "%s", &name[off]);
+
+	/*
+	 * Call device_register(tl_hba->dev) to register the emulated
+	 * Linux/SCSI LLD of type struct Scsi_Host at tl_hba->sh after
+	 * device_register() callbacks in tcm_loop_driver_probe()
+	 */
+	ret = tcm_loop_setup_hba_bus(tl_hba, tcm_loop_hba_no_cnt);
+	if (ret)
+		goto out;
+
+	sh = tl_hba->sh;
+	tcm_loop_hba_no_cnt++;
+	printk(KERN_INFO "TCM_Loop_ConfigFS: Allocated emulated Target"
+		" %s Address: %s at Linux/SCSI Host ID: %d\n",
+		tcm_loop_dump_proto_id(tl_hba), name, sh->host_no);
+
+	return &tl_hba->tl_hba_wwn;
+out:
+	kfree(tl_hba);
+	return ERR_PTR(ret);
+}
+
+void tcm_loop_drop_scsi_hba(
+	struct se_wwn *wwn)
+{
+	struct tcm_loop_hba *tl_hba = container_of(wwn,
+				struct tcm_loop_hba, tl_hba_wwn);
+	int host_no = tl_hba->sh->host_no;
+	/*
+	 * Call device_unregister() on the original tl_hba->dev.
+	 * tcm_loop_fabric_scsi.c:tcm_loop_release_adapter() will
+	 * release *tl_hba;
+	 */
+	device_unregister(&tl_hba->dev);
+
+	printk(KERN_INFO "TCM_Loop_ConfigFS: Deallocated emulated Target"
+		" SAS Address: %s at Linux/SCSI Host ID: %d\n",
+		config_item_name(&wwn->wwn_group.cg_item), host_no);
+}
+
+/* Start items for tcm_loop_cit */
+static ssize_t tcm_loop_wwn_show_attr_version(
+	struct target_fabric_configfs *tf,
+	char *page)
+{
+	return sprintf(page, "TCM Loopback Fabric module %s\n", TCM_LOOP_VERSION);
+}
+
+TF_WWN_ATTR_RO(tcm_loop, version);
+
+static struct configfs_attribute *tcm_loop_wwn_attrs[] = {
+	&tcm_loop_wwn_version.attr,
+	NULL,
+};
+
+/* End items for tcm_loop_cit */
+
+static int tcm_loop_register_configfs(void)
+{
+	struct target_fabric_configfs *fabric;
+	struct config_group *tf_cg;
+	int ret;
+	/*
+	 * Set the TCM Loop HBA counter to zero
+	 */
+	tcm_loop_hba_no_cnt = 0;
+	/*
+	 * Register the top level struct config_item_type with TCM core
+	 */
+	fabric = target_fabric_configfs_init(THIS_MODULE, "loopback");
+	if (!fabric) {
+		printk(KERN_ERR "tcm_loop_register_configfs() failed!\n");
+		return -1;
+	}
+	/*
+	 * Setup the fabric API of function pointers used by target_core_mod
+	 */
+	fabric->tf_ops.get_fabric_name = &tcm_loop_get_fabric_name;
+	fabric->tf_ops.get_fabric_proto_ident = &tcm_loop_get_fabric_proto_ident;
+	fabric->tf_ops.tpg_get_wwn = &tcm_loop_get_endpoint_wwn;
+	fabric->tf_ops.tpg_get_tag = &tcm_loop_get_tag;
+	fabric->tf_ops.tpg_get_default_depth = &tcm_loop_get_default_depth;
+	fabric->tf_ops.tpg_get_pr_transport_id = &tcm_loop_get_pr_transport_id;
+	fabric->tf_ops.tpg_get_pr_transport_id_len =
+					&tcm_loop_get_pr_transport_id_len;
+	fabric->tf_ops.tpg_parse_pr_out_transport_id =
+					&tcm_loop_parse_pr_out_transport_id;
+	fabric->tf_ops.tpg_check_demo_mode = &tcm_loop_check_demo_mode;
+	fabric->tf_ops.tpg_check_demo_mode_cache =
+					&tcm_loop_check_demo_mode_cache;
+	fabric->tf_ops.tpg_check_demo_mode_write_protect =
+					&tcm_loop_check_demo_mode_write_protect;
+	fabric->tf_ops.tpg_check_prod_mode_write_protect =
+					&tcm_loop_check_prod_mode_write_protect;
+	/*
+	 * The TCM loopback fabric module runs in demo-mode to a local
+	 * virtual SCSI device, so fabric dependent initator ACLs are
+	 * not required.
+	 */
+	fabric->tf_ops.tpg_alloc_fabric_acl = &tcm_loop_tpg_alloc_fabric_acl;
+	fabric->tf_ops.tpg_release_fabric_acl =
+					&tcm_loop_tpg_release_fabric_acl;
+	fabric->tf_ops.tpg_get_inst_index = &tcm_loop_get_inst_index;
+	/*
+	 * Since tcm_loop is mapping physical memory from Linux/SCSI
+	 * struct scatterlist arrays for each struct scsi_cmnd I/O,
+	 * we do not need TCM to allocate a iovec array for
+	 * virtual memory address mappings
+	 */
+	fabric->tf_ops.alloc_cmd_iovecs = NULL;
+	/*
+	 * Used for setting up remaining TCM resources in process context
+	 */
+	fabric->tf_ops.new_cmd_map = &tcm_loop_new_cmd_map;
+	fabric->tf_ops.check_stop_free = &tcm_loop_check_stop_free;
+	fabric->tf_ops.release_cmd_to_pool = &tcm_loop_deallocate_core_cmd;
+	fabric->tf_ops.release_cmd_direct = &tcm_loop_deallocate_core_cmd;
+	fabric->tf_ops.shutdown_session = &tcm_loop_shutdown_session;
+	fabric->tf_ops.close_session = &tcm_loop_close_session;
+	fabric->tf_ops.stop_session = &tcm_loop_stop_session;
+	fabric->tf_ops.fall_back_to_erl0 = &tcm_loop_fall_back_to_erl0;
+	fabric->tf_ops.sess_logged_in = &tcm_loop_sess_logged_in;
+	fabric->tf_ops.sess_get_index = &tcm_loop_sess_get_index;
+	fabric->tf_ops.sess_get_initiator_sid = NULL;
+	fabric->tf_ops.write_pending = &tcm_loop_write_pending;
+	fabric->tf_ops.write_pending_status = &tcm_loop_write_pending_status;
+	/*
+	 * Not used for TCM loopback
+	 */
+	fabric->tf_ops.set_default_node_attributes =
+					&tcm_loop_set_default_node_attributes;
+	fabric->tf_ops.get_task_tag = &tcm_loop_get_task_tag;
+	fabric->tf_ops.get_cmd_state = &tcm_loop_get_cmd_state;
+	fabric->tf_ops.new_cmd_failure = &tcm_loop_new_cmd_failure;
+	fabric->tf_ops.queue_data_in = &tcm_loop_queue_data_in;
+	fabric->tf_ops.queue_status = &tcm_loop_queue_status;
+	fabric->tf_ops.queue_tm_rsp = &tcm_loop_queue_tm_rsp;
+	fabric->tf_ops.set_fabric_sense_len = &tcm_loop_set_fabric_sense_len;
+	fabric->tf_ops.get_fabric_sense_len = &tcm_loop_get_fabric_sense_len;
+	fabric->tf_ops.is_state_remove = &tcm_loop_is_state_remove;
+	fabric->tf_ops.pack_lun = &tcm_loop_pack_lun;
+
+	tf_cg = &fabric->tf_group;
+	/*
+	 * Setup function pointers for generic logic in target_core_fabric_configfs.c
+	 */
+	fabric->tf_ops.fabric_make_wwn = &tcm_loop_make_scsi_hba;
+	fabric->tf_ops.fabric_drop_wwn = &tcm_loop_drop_scsi_hba;
+	fabric->tf_ops.fabric_make_tpg = &tcm_loop_make_naa_tpg;
+	fabric->tf_ops.fabric_drop_tpg = &tcm_loop_drop_naa_tpg;
+	/*
+	 * fabric_post_link() and fabric_pre_unlink() are used for
+	 * registration and release of TCM Loop Virtual SCSI LUNs.
+	 */
+	fabric->tf_ops.fabric_post_link = &tcm_loop_port_link;
+	fabric->tf_ops.fabric_pre_unlink = &tcm_loop_port_unlink;
+	fabric->tf_ops.fabric_make_np = NULL;
+	fabric->tf_ops.fabric_drop_np = NULL;
+	/*
+	 * Setup default attribute lists for various fabric->tf_cit_tmpl
+	 */
+	TF_CIT_TMPL(fabric)->tfc_wwn_cit.ct_attrs = tcm_loop_wwn_attrs;
+	TF_CIT_TMPL(fabric)->tfc_tpg_base_cit.ct_attrs = tcm_loop_tpg_attrs;
+	TF_CIT_TMPL(fabric)->tfc_tpg_attrib_cit.ct_attrs = NULL;
+	TF_CIT_TMPL(fabric)->tfc_tpg_param_cit.ct_attrs = NULL;
+	TF_CIT_TMPL(fabric)->tfc_tpg_np_base_cit.ct_attrs = NULL;
+	/*
+	 * Once fabric->tf_ops has been setup, now register the fabric for
+	 * use within TCM
+	 */
+	ret = target_fabric_configfs_register(fabric);
+	if (ret < 0) {
+		printk(KERN_ERR "target_fabric_configfs_register() for"
+				" TCM_Loop failed!\n");
+		target_fabric_configfs_free(fabric);
+		return -1;
+	}
+	/*
+	 * Setup our local pointer to *fabric.
+	 */
+	tcm_loop_fabric_configfs = fabric;
+	printk(KERN_INFO "TCM_LOOP[0] - Set fabric ->"
+			" tcm_loop_fabric_configfs\n");
+	return 0;
+}
+
+static void tcm_loop_deregister_configfs(void)
+{
+	if (!tcm_loop_fabric_configfs)
+		return;
+
+	target_fabric_configfs_deregister(tcm_loop_fabric_configfs);
+	tcm_loop_fabric_configfs = NULL;
+	printk(KERN_INFO "TCM_LOOP[0] - Cleared"
+				" tcm_loop_fabric_configfs\n");
+}
+
+static int __init tcm_loop_fabric_init(void)
+{
+	int ret;
+
+	tcm_loop_cmd_cache = kmem_cache_create("tcm_loop_cmd_cache",
+				sizeof(struct tcm_loop_cmd),
+				__alignof__(struct tcm_loop_cmd),
+				0, NULL);
+	if (!tcm_loop_cmd_cache) {
+		printk(KERN_ERR "kmem_cache_create() for"
+			" tcm_loop_cmd_cache failed\n");
+		return -ENOMEM;
+	}
+
+	ret = tcm_loop_alloc_core_bus();
+	if (ret)
+		return ret;
+
+	ret = tcm_loop_register_configfs();
+	if (ret) {
+		tcm_loop_release_core_bus();
+		return ret;
+	}
+
+	return 0;
+}
+
+static void __exit tcm_loop_fabric_exit(void)
+{
+	tcm_loop_deregister_configfs();
+	tcm_loop_release_core_bus();
+	kmem_cache_destroy(tcm_loop_cmd_cache);
+}
+
+MODULE_DESCRIPTION("TCM loopback virtual Linux/SCSI fabric module");
+MODULE_AUTHOR("Nicholas A. Bellinger <nab@risingtidesystems.com>");
+MODULE_LICENSE("GPL");
+module_init(tcm_loop_fabric_init);
+module_exit(tcm_loop_fabric_exit);
diff --git a/drivers/target/loopback/tcm_loop.h b/drivers/target/loopback/tcm_loop.h
new file mode 100644
index 0000000..7e9f7ab
--- /dev/null
+++ b/drivers/target/loopback/tcm_loop.h
@@ -0,0 +1,77 @@
+#define TCM_LOOP_VERSION		"v2.1-rc1"
+#define TL_WWN_ADDR_LEN			256
+#define TL_TPGS_PER_HBA			32
+/*
+ * Defaults for struct scsi_host_template tcm_loop_driver_template
+ *
+ * We use large can_queue and cmd_per_lun here and let TCM enforce
+ * the underlying se_device_t->queue_depth.
+ */
+#define TL_SCSI_CAN_QUEUE		1024
+#define TL_SCSI_CMD_PER_LUN		1024
+#define TL_SCSI_MAX_SECTORS		1024
+#define TL_SCSI_SG_TABLESIZE		256
+/*
+ * Used in tcm_loop_driver_probe() for struct Scsi_Host->max_cmd_len
+ */
+#define TL_SCSI_MAX_CMD_LEN		32
+
+#ifdef CONFIG_LOOPBACK_TARGET_CDB_DEBUG
+# define TL_CDB_DEBUG(x...)		printk(KERN_INFO x)
+#else
+# define TL_CDB_DEBUG(x...)
+#endif
+
+struct tcm_loop_cmd {
+	/* State of Linux/SCSI CDB+Data descriptor */
+	u32 sc_cmd_state;
+	/* Pointer to the CDB+Data descriptor from Linux/SCSI subsystem */
+	struct scsi_cmnd *sc;
+	struct list_head *tl_cmd_list;
+	/* The TCM I/O descriptor that is accessed via container_of() */
+	struct se_cmd tl_se_cmd;
+	/* Sense buffer that will be mapped into outgoing status */
+	unsigned char tl_sense_buf[TRANSPORT_SENSE_BUFFER];
+};
+
+struct tcm_loop_tmr {
+	atomic_t tmr_complete;
+	wait_queue_head_t tl_tmr_wait;
+};
+
+struct tcm_loop_nexus {
+	int it_nexus_active;
+	/*
+	 * Pointer to Linux/SCSI HBA from linux/include/scsi_host.h
+	 */
+	struct scsi_host *sh;
+	/*
+	 * Pointer to TCM session for I_T Nexus
+	 */
+	struct se_session *se_sess;
+};
+
+struct tcm_loop_nacl {
+	struct se_node_acl se_node_acl;
+};
+
+struct tcm_loop_tpg {
+	unsigned short tl_tpgt;
+	atomic_t tl_tpg_port_count;
+	struct se_portal_group tl_se_tpg;
+	struct tcm_loop_hba *tl_hba;
+};
+
+struct tcm_loop_hba {
+	u8 tl_proto_id;
+	unsigned char tl_wwn_address[TL_WWN_ADDR_LEN];
+	struct se_hba_s *se_hba;
+	struct se_lun *tl_hba_lun;
+	struct se_port *tl_hba_lun_sep;
+	struct se_device_s *se_dev_hba_ptr;
+	struct tcm_loop_nexus *tl_nexus;
+	struct device dev;
+	struct Scsi_Host *sh;
+	struct tcm_loop_tpg tl_hba_tpgs[TL_TPGS_PER_HBA];
+	struct se_wwn tl_hba_wwn;
+};