/*******************************************************************************
 *
 * This file contains the Linux/SCSI LLD virtual SCSI initiator driver
 * for emulated SAS initiator ports
 *
 * © Copyright 2011-2013 Datera, Inc.
 *
 * 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 <target/target_core_base.h>
#include <target/target_core_fabric.h>

#include "tcm_loop.h"

#define to_tcm_loop_hba(hba)    container_of(hba, struct tcm_loop_hba, dev)

static struct workqueue_struct *tcm_loop_workqueue;
static struct kmem_cache *tcm_loop_cmd_cache;

static int tcm_loop_hba_no_cnt;

static int tcm_loop_queue_status(struct se_cmd *se_cmd);

/*
 * Called from struct target_core_fabric_ops->check_stop_free()
 */
static int tcm_loop_check_stop_free(struct se_cmd *se_cmd)
{
        return transport_generic_free_cmd(se_cmd, 0);
}

static void tcm_loop_release_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_show_info(struct seq_file *m, struct Scsi_Host *host)
{
        seq_puts(m, "tcm_loop_proc_info()\n");
        return 0;
}

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
 */
static struct device *tcm_loop_primary;

static void tcm_loop_submission_work(struct work_struct *work)
{
        struct tcm_loop_cmd *tl_cmd =
                container_of(work, struct tcm_loop_cmd, work);
        struct se_cmd *se_cmd = &tl_cmd->tl_se_cmd;
        struct scsi_cmnd *sc = tl_cmd->sc;
        struct tcm_loop_nexus *tl_nexus;
        struct tcm_loop_hba *tl_hba;
        struct tcm_loop_tpg *tl_tpg;
        struct scatterlist *sgl_bidi = NULL;
        u32 sgl_bidi_count = 0, transfer_length;
        int rc;

        tl_hba = *(struct tcm_loop_hba **)shost_priv(sc->device->host);
        tl_tpg = &tl_hba->tl_hba_tpgs[sc->device->id];

        /*
         * Ensure that this tl_tpg reference from the incoming sc->device->id
         * has already been configured via tcm_loop_make_naa_tpg().
         */
        if (!tl_tpg->tl_hba) {
                set_host_byte(sc, DID_NO_CONNECT);
                goto out_done;
        }
        if (tl_tpg->tl_transport_status == TCM_TRANSPORT_OFFLINE) {
                set_host_byte(sc, DID_TRANSPORT_DISRUPTED);
                goto out_done;
        }
        tl_nexus = tl_tpg->tl_nexus;
        if (!tl_nexus) {
                scmd_printk(KERN_ERR, sc,
                            "TCM_Loop I_T Nexus does not exist\n");
                set_host_byte(sc, DID_ERROR);
                goto out_done;
        }

        transfer_length = scsi_transfer_length(sc);
        if (!scsi_prot_sg_count(sc) &&
            scsi_get_prot_op(sc) != SCSI_PROT_NORMAL) {
                se_cmd->prot_pto = true;
                /*
                 * loopback transport doesn't support
                 * WRITE_GENERATE, READ_STRIP protection
                 * information operations, go ahead unprotected.
                 */
                transfer_length = scsi_bufflen(sc);
        }

        se_cmd->tag = tl_cmd->sc_cmd_tag;
        rc = target_submit_cmd_map_sgls(se_cmd, tl_nexus->se_sess, sc->cmnd,
                        &tl_cmd->tl_sense_buf[0], tl_cmd->sc->device->lun,
                        transfer_length, TCM_SIMPLE_TAG,
                        sc->sc_data_direction, 0,
                        scsi_sglist(sc), scsi_sg_count(sc),
                        sgl_bidi, sgl_bidi_count,
                        scsi_prot_sglist(sc), scsi_prot_sg_count(sc));
        if (rc < 0) {
                set_host_byte(sc, DID_NO_CONNECT);
                goto out_done;
        }
        return;

out_done:
        kmem_cache_free(tcm_loop_cmd_cache, tl_cmd);
        sc->scsi_done(sc);
}

/*
 * ->queuecommand can be and usually is called from interrupt context, so
 * defer the actual submission to a workqueue.
 */
static int tcm_loop_queuecommand(struct Scsi_Host *sh, struct scsi_cmnd *sc)
{
        struct tcm_loop_cmd *tl_cmd;

        pr_debug("%s() %d:%d:%d:%llu got CDB: 0x%02x scsi_buf_len: %u\n",
                 __func__, sc->device->host->host_no, sc->device->id,
                 sc->device->channel, sc->device->lun, sc->cmnd[0],
                 scsi_bufflen(sc));

        tl_cmd = kmem_cache_zalloc(tcm_loop_cmd_cache, GFP_ATOMIC);
        if (!tl_cmd) {
                set_host_byte(sc, DID_ERROR);
                sc->scsi_done(sc);
                return 0;
        }

        tl_cmd->sc = sc;
        tl_cmd->sc_cmd_tag = sc->request->tag;
        INIT_WORK(&tl_cmd->work, tcm_loop_submission_work);
        queue_work(tcm_loop_workqueue, &tl_cmd->work);
        return 0;
}

/*
 * Called from SCSI EH process context to issue a LUN_RESET TMR
 * to struct scsi_device
 */
static int tcm_loop_issue_tmr(struct tcm_loop_tpg *tl_tpg,
                              u64 lun, int task, enum tcm_tmreq_table tmr)
{
        struct se_cmd *se_cmd;
        struct se_session *se_sess;
        struct tcm_loop_nexus *tl_nexus;
        struct tcm_loop_cmd *tl_cmd;
        int ret = TMR_FUNCTION_FAILED, rc;

        /*
         * Locate the tl_nexus and se_sess pointers
         */
        tl_nexus = tl_tpg->tl_nexus;
        if (!tl_nexus) {
                pr_err("Unable to perform device reset without active I_T Nexus\n");
                return ret;
        }

        tl_cmd = kmem_cache_zalloc(tcm_loop_cmd_cache, GFP_KERNEL);
        if (!tl_cmd)
                return ret;

        init_completion(&tl_cmd->tmr_done);

        se_cmd = &tl_cmd->tl_se_cmd;
        se_sess = tl_tpg->tl_nexus->se_sess;

        rc = target_submit_tmr(se_cmd, se_sess, tl_cmd->tl_sense_buf, lun,
                               NULL, tmr, GFP_KERNEL, task,
                               TARGET_SCF_ACK_KREF);
        if (rc < 0)
                goto release;
        wait_for_completion(&tl_cmd->tmr_done);
        ret = se_cmd->se_tmr_req->response;
        target_put_sess_cmd(se_cmd);

out:
        return ret;

release:
        kmem_cache_free(tcm_loop_cmd_cache, tl_cmd);
        goto out;
}

static int tcm_loop_abort_task(struct scsi_cmnd *sc)
{
        struct tcm_loop_hba *tl_hba;
        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);
        tl_tpg = &tl_hba->tl_hba_tpgs[sc->device->id];
        ret = tcm_loop_issue_tmr(tl_tpg, sc->device->lun,
                                 sc->request->tag, TMR_ABORT_TASK);
        return (ret == TMR_FUNCTION_COMPLETE) ? SUCCESS : FAILED;
}

/*
 * 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 tcm_loop_hba *tl_hba;
        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);
        tl_tpg = &tl_hba->tl_hba_tpgs[sc->device->id];

        ret = tcm_loop_issue_tmr(tl_tpg, sc->device->lun,
                                 0, TMR_LUN_RESET);
        return (ret == TMR_FUNCTION_COMPLETE) ? SUCCESS : FAILED;
}

static int tcm_loop_target_reset(struct scsi_cmnd *sc)
{
        struct tcm_loop_hba *tl_hba;
        struct tcm_loop_tpg *tl_tpg;

        /*
         * Locate the tcm_loop_hba_t pointer
         */
        tl_hba = *(struct tcm_loop_hba **)shost_priv(sc->device->host);
        if (!tl_hba) {
                pr_err("Unable to perform device reset without active I_T Nexus\n");
                return FAILED;
        }
        /*
         * Locate the tl_tpg pointer from TargetID in sc->device->id
         */
        tl_tpg = &tl_hba->tl_hba_tpgs[sc->device->id];
        if (tl_tpg) {
                tl_tpg->tl_transport_status = TCM_TRANSPORT_ONLINE;
                return SUCCESS;
        }
        return FAILED;
}

static struct scsi_host_template tcm_loop_driver_template = {
        .show_info              = tcm_loop_show_info,
        .proc_name              = "tcm_loopback",
        .name                   = "TCM_Loopback",
        .queuecommand           = tcm_loop_queuecommand,
        .change_queue_depth     = scsi_change_queue_depth,
        .eh_abort_handler = tcm_loop_abort_task,
        .eh_device_reset_handler = tcm_loop_device_reset,
        .eh_target_reset_handler = tcm_loop_target_reset,
        .can_queue              = 1024,
        .this_id                = -1,
        .sg_tablesize           = 256,
        .cmd_per_lun            = 1024,
        .max_sectors            = 0xFFFF,
        .dma_boundary           = PAGE_SIZE - 1,
        .module                 = THIS_MODULE,
        .track_queue_depth      = 1,
};

static int tcm_loop_driver_probe(struct device *dev)
{
        struct tcm_loop_hba *tl_hba;
        struct Scsi_Host *sh;
        int error, host_prot;

        tl_hba = to_tcm_loop_hba(dev);

        sh = scsi_host_alloc(&tcm_loop_driver_template,
                        sizeof(struct tcm_loop_hba));
        if (!sh) {
                pr_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 = SCSI_MAX_VARLEN_CDB_SIZE;

        host_prot = SHOST_DIF_TYPE1_PROTECTION | SHOST_DIF_TYPE2_PROTECTION |
                    SHOST_DIF_TYPE3_PROTECTION | SHOST_DIX_TYPE1_PROTECTION |
                    SHOST_DIX_TYPE2_PROTECTION | SHOST_DIX_TYPE3_PROTECTION;

        scsi_host_set_prot(sh, host_prot);
        scsi_host_set_guard(sh, SHOST_DIX_GUARD_CRC);

        error = scsi_add_host(sh, &tl_hba->dev);
        if (error) {
                pr_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) {
                pr_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)) {
                pr_err("Unable to allocate tcm_loop_primary\n");
                return PTR_ERR(tcm_loop_primary);
        }

        ret = bus_register(&tcm_loop_lld_bus);
        if (ret) {
                pr_err("bus_register() failed for tcm_loop_lld_bus\n");
                goto dev_unreg;
        }

        ret = driver_register(&tcm_loop_driverfs);
        if (ret) {
                pr_err("driver_register() failed for tcm_loop_driverfs\n");
                goto bus_unreg;
        }

        pr_debug("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);

        pr_debug("Releasing TCM Loop Core BUS\n");
}

static inline struct tcm_loop_tpg *tl_tpg(struct se_portal_group *se_tpg)
{
        return container_of(se_tpg, struct tcm_loop_tpg, tl_se_tpg);
}

static char *tcm_loop_get_endpoint_wwn(struct se_portal_group *se_tpg)
{
        /*
         * Return the passed NAA identifier for the Target Port
         */
        return &tl_tpg(se_tpg)->tl_hba->tl_wwn_address[0];
}

static u16 tcm_loop_get_tag(struct se_portal_group *se_tpg)
{
        /*
         * This Tag is used when forming SCSI Name identifier in EVPD=1 0x83
         * to represent the SCSI Target Port.
         */
        return tl_tpg(se_tpg)->tl_tpgt;
}

/*
 * 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 int tcm_loop_check_prot_fabric_only(struct se_portal_group *se_tpg)
{
        struct tcm_loop_tpg *tl_tpg = container_of(se_tpg, struct tcm_loop_tpg,
                                                   tl_se_tpg);
        return tl_tpg->tl_fabric_prot_type;
}

static u32 tcm_loop_get_inst_index(struct se_portal_group *se_tpg)
{
        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 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_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.
         */
        target_execute_cmd(se_cmd);
        return 0;
}

static int tcm_loop_queue_data_or_status(const char *func,
                struct se_cmd *se_cmd, u8 scsi_status)
{
        struct tcm_loop_cmd *tl_cmd = container_of(se_cmd,
                                struct tcm_loop_cmd, tl_se_cmd);
        struct scsi_cmnd *sc = tl_cmd->sc;

        pr_debug("%s() called for scsi_cmnd: %p cdb: 0x%02x\n",
                 func, 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(sc->sense_buffer, se_cmd->sense_buffer,
                                SCSI_SENSE_BUFFERSIZE);
                sc->result = SAM_STAT_CHECK_CONDITION;
                set_driver_byte(sc, DRIVER_SENSE);
        } else
                sc->result = scsi_status;

        set_host_byte(sc, DID_OK);
        if ((se_cmd->se_cmd_flags & SCF_OVERFLOW_BIT) ||
            (se_cmd->se_cmd_flags & SCF_UNDERFLOW_BIT))
                scsi_set_resid(sc, se_cmd->residual_count);
        sc->scsi_done(sc);
        return 0;
}

static int tcm_loop_queue_data_in(struct se_cmd *se_cmd)
{
        return tcm_loop_queue_data_or_status(__func__, se_cmd, SAM_STAT_GOOD);
}

static int tcm_loop_queue_status(struct se_cmd *se_cmd)
{
        return tcm_loop_queue_data_or_status(__func__,
                                             se_cmd, se_cmd->scsi_status);
}

static void tcm_loop_queue_tm_rsp(struct se_cmd *se_cmd)
{
        struct tcm_loop_cmd *tl_cmd = container_of(se_cmd,
                                struct tcm_loop_cmd, tl_se_cmd);

        /* Wake up tcm_loop_issue_tmr(). */
        complete(&tl_cmd->tmr_done);
}

static void tcm_loop_aborted_task(struct se_cmd *se_cmd)
{
        return;
}

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_mb(&tl_tpg->tl_tpg_port_count);
        /*
         * Add Linux/SCSI struct scsi_device by HCTL
         */
        scsi_add_device(tl_hba->sh, 0, tl_tpg->tl_tpgt, lun->unpacked_lun);

        pr_debug("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) {
                pr_err("Unable to locate struct scsi_device for %d:%d:%llu\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_mb(&tl_tpg->tl_tpg_port_count);

        pr_debug("TCM_Loop_ConfigFS: Port Unlink Successful\n");
}

/* End items for tcm_loop_port_cit */

static ssize_t tcm_loop_tpg_attrib_fabric_prot_type_show(
                struct config_item *item, char *page)
{
        struct se_portal_group *se_tpg = attrib_to_tpg(item);
        struct tcm_loop_tpg *tl_tpg = container_of(se_tpg, struct tcm_loop_tpg,
                                                   tl_se_tpg);

        return sprintf(page, "%d\n", tl_tpg->tl_fabric_prot_type);
}

static ssize_t tcm_loop_tpg_attrib_fabric_prot_type_store(
                struct config_item *item, const char *page, size_t count)
{
        struct se_portal_group *se_tpg = attrib_to_tpg(item);
        struct tcm_loop_tpg *tl_tpg = container_of(se_tpg, struct tcm_loop_tpg,
                                                   tl_se_tpg);
        unsigned long val;
        int ret = kstrtoul(page, 0, &val);

        if (ret) {
                pr_err("kstrtoul() returned %d for fabric_prot_type\n", ret);
                return ret;
        }
        if (val != 0 && val != 1 && val != 3) {
                pr_err("Invalid qla2xxx fabric_prot_type: %lu\n", val);
                return -EINVAL;
        }
        tl_tpg->tl_fabric_prot_type = val;

        return count;
}

CONFIGFS_ATTR(tcm_loop_tpg_attrib_, fabric_prot_type);

static struct configfs_attribute *tcm_loop_tpg_attrib_attrs[] = {
        &tcm_loop_tpg_attrib_attr_fabric_prot_type,
        NULL,
};

/* Start items for tcm_loop_nexus_cit */

static int tcm_loop_alloc_sess_cb(struct se_portal_group *se_tpg,
                                  struct se_session *se_sess, void *p)
{
        struct tcm_loop_tpg *tl_tpg = container_of(se_tpg,
                                        struct tcm_loop_tpg, tl_se_tpg);

        tl_tpg->tl_nexus = p;
        return 0;
}

static int tcm_loop_make_nexus(
        struct tcm_loop_tpg *tl_tpg,
        const char *name)
{
        struct tcm_loop_hba *tl_hba = tl_tpg->tl_hba;
        struct tcm_loop_nexus *tl_nexus;
        int ret;

        if (tl_tpg->tl_nexus) {
                pr_debug("tl_tpg->tl_nexus already exists\n");
                return -EEXIST;
        }

        tl_nexus = kzalloc(sizeof(*tl_nexus), GFP_KERNEL);
        if (!tl_nexus)
                return -ENOMEM;

        tl_nexus->se_sess = target_setup_session(&tl_tpg->tl_se_tpg, 0, 0,
                                        TARGET_PROT_DIN_PASS | TARGET_PROT_DOUT_PASS,
                                        name, tl_nexus, tcm_loop_alloc_sess_cb);
        if (IS_ERR(tl_nexus->se_sess)) {
                ret = PTR_ERR(tl_nexus->se_sess);
                kfree(tl_nexus);
                return ret;
        }

        pr_debug("TCM_Loop_ConfigFS: Established I_T Nexus to emulated %s Initiator Port: %s\n",
                 tcm_loop_dump_proto_id(tl_hba), name);
        return 0;
}

static int tcm_loop_drop_nexus(
        struct tcm_loop_tpg *tpg)
{
        struct se_session *se_sess;
        struct tcm_loop_nexus *tl_nexus;

        tl_nexus = tpg->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)) {
                pr_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;
        }

        pr_debug("TCM_Loop_ConfigFS: Removing I_T Nexus to emulated %s Initiator Port: %s\n",
                 tcm_loop_dump_proto_id(tpg->tl_hba),
                 tl_nexus->se_sess->se_node_acl->initiatorname);
        /*
         * Release the SCSI I_T Nexus to the emulated Target Port
         */
        target_remove_session(se_sess);
        tpg->tl_nexus = NULL;
        kfree(tl_nexus);
        return 0;
}

/* End items for tcm_loop_nexus_cit */

static ssize_t tcm_loop_tpg_nexus_show(struct config_item *item, char *page)
{
        struct se_portal_group *se_tpg = to_tpg(item);
        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_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_nexus_store(struct config_item *item,
                const char *page, size_t count)
{
        struct se_portal_group *se_tpg = to_tpg(item);
        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) {
                pr_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) {
                        pr_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) {
                        pr_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) {
                        pr_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;
        }
        pr_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;
}

static ssize_t tcm_loop_tpg_transport_status_show(struct config_item *item,
                char *page)
{
        struct se_portal_group *se_tpg = to_tpg(item);
        struct tcm_loop_tpg *tl_tpg = container_of(se_tpg,
                        struct tcm_loop_tpg, tl_se_tpg);
        const char *status = NULL;
        ssize_t ret = -EINVAL;

        switch (tl_tpg->tl_transport_status) {
        case TCM_TRANSPORT_ONLINE:
                status = "online";
                break;
        case TCM_TRANSPORT_OFFLINE:
                status = "offline";
                break;
        default:
                break;
        }

        if (status)
                ret = snprintf(page, PAGE_SIZE, "%s\n", status);

        return ret;
}

static ssize_t tcm_loop_tpg_transport_status_store(struct config_item *item,
                const char *page, size_t count)
{
        struct se_portal_group *se_tpg = to_tpg(item);
        struct tcm_loop_tpg *tl_tpg = container_of(se_tpg,
                        struct tcm_loop_tpg, tl_se_tpg);

        if (!strncmp(page, "online", 6)) {
                tl_tpg->tl_transport_status = TCM_TRANSPORT_ONLINE;
                return count;
        }
        if (!strncmp(page, "offline", 7)) {
                tl_tpg->tl_transport_status = TCM_TRANSPORT_OFFLINE;
                if (tl_tpg->tl_nexus) {
                        struct se_session *tl_sess = tl_tpg->tl_nexus->se_sess;

                        core_allocate_nexus_loss_ua(tl_sess->se_node_acl);
                }
                return count;
        }
        return -EINVAL;
}

static ssize_t tcm_loop_tpg_address_show(struct config_item *item,
                                         char *page)
{
        struct se_portal_group *se_tpg = to_tpg(item);
        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;

        return snprintf(page, PAGE_SIZE, "%d:0:%d\n",
                        tl_hba->sh->host_no, tl_tpg->tl_tpgt);
}

CONFIGFS_ATTR(tcm_loop_tpg_, nexus);
CONFIGFS_ATTR(tcm_loop_tpg_, transport_status);
CONFIGFS_ATTR_RO(tcm_loop_tpg_, address);

static struct configfs_attribute *tcm_loop_tpg_attrs[] = {
        &tcm_loop_tpg_attr_nexus,
        &tcm_loop_tpg_attr_transport_status,
        &tcm_loop_tpg_attr_address,
        NULL,
};

/* Start items for tcm_loop_naa_cit */

static struct se_portal_group *tcm_loop_make_naa_tpg(struct se_wwn *wwn,
                                                     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;
        int ret;
        unsigned long tpgt;

        if (strstr(name, "tpgt_") != name) {
                pr_err("Unable to locate \"tpgt_#\" directory group\n");
                return ERR_PTR(-EINVAL);
        }
        if (kstrtoul(name+5, 10, &tpgt))
                return ERR_PTR(-EINVAL);

        if (tpgt >= TL_TPGS_PER_HBA) {
                pr_err("Passed tpgt: %lu 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 TCM Target Endpoint
         */
        ret = core_tpg_register(wwn, &tl_tpg->tl_se_tpg, tl_hba->tl_proto_id);
        if (ret < 0)
                return ERR_PTR(-ENOMEM);

        pr_debug("TCM_Loop_ConfigFS: Allocated Emulated %s Target Port %s,t,0x%04lx\n",
                 tcm_loop_dump_proto_id(tl_hba),
                 config_item_name(&wwn->wwn_group.cg_item), tpgt);
        return &tl_tpg->tl_se_tpg;
}

static 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 target link if present
         */
        tcm_loop_drop_nexus(tl_tpg);
        /*
         * Deregister the tl_tpg as a emulated TCM Target Endpoint
         */
        core_tpg_deregister(se_tpg);

        tl_tpg->tl_hba = NULL;
        tl_tpg->tl_tpgt = 0;

        pr_debug("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 */

static 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(*tl_hba), GFP_KERNEL);
        if (!tl_hba)
                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) {
                pr_err("Unable to locate prefix for emulated Target Port: %s\n",
                       name);
                ret = -EINVAL;
                goto out;
        }
        tl_hba->tl_proto_id = SCSI_PROTOCOL_ISCSI;

check_len:
        if (strlen(name) >= TL_WWN_ADDR_LEN) {
                pr_err("Emulated NAA %s Address: %s, exceeds max: %d\n",
                       name, tcm_loop_dump_proto_id(tl_hba), TL_WWN_ADDR_LEN);
                ret = -EINVAL;
                goto out;
        }
        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++;
        pr_debug("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);
}

static 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);

        pr_debug("TCM_Loop_ConfigFS: Deallocating emulated Target %s Address: %s at Linux/SCSI Host ID: %d\n",
                 tcm_loop_dump_proto_id(tl_hba), tl_hba->tl_wwn_address,
                 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);
}

/* Start items for tcm_loop_cit */
static ssize_t tcm_loop_wwn_version_show(struct config_item *item, char *page)
{
        return sprintf(page, "TCM Loopback Fabric module %s\n", TCM_LOOP_VERSION);
}

CONFIGFS_ATTR_RO(tcm_loop_wwn_, version);

static struct configfs_attribute *tcm_loop_wwn_attrs[] = {
        &tcm_loop_wwn_attr_version,
        NULL,
};

/* End items for tcm_loop_cit */

static const struct target_core_fabric_ops loop_ops = {
        .module                         = THIS_MODULE,
        .fabric_name                    = "loopback",
        .tpg_get_wwn                    = tcm_loop_get_endpoint_wwn,
        .tpg_get_tag                    = tcm_loop_get_tag,
        .tpg_check_demo_mode            = tcm_loop_check_demo_mode,
        .tpg_check_demo_mode_cache      = tcm_loop_check_demo_mode_cache,
        .tpg_check_demo_mode_write_protect =
                                tcm_loop_check_demo_mode_write_protect,
        .tpg_check_prod_mode_write_protect =
                                tcm_loop_check_prod_mode_write_protect,
        .tpg_check_prot_fabric_only     = tcm_loop_check_prot_fabric_only,
        .tpg_get_inst_index             = tcm_loop_get_inst_index,
        .check_stop_free                = tcm_loop_check_stop_free,
        .release_cmd                    = tcm_loop_release_cmd,
        .sess_get_index                 = tcm_loop_sess_get_index,
        .write_pending                  = tcm_loop_write_pending,
        .set_default_node_attributes    = tcm_loop_set_default_node_attributes,
        .get_cmd_state                  = tcm_loop_get_cmd_state,
        .queue_data_in                  = tcm_loop_queue_data_in,
        .queue_status                   = tcm_loop_queue_status,
        .queue_tm_rsp                   = tcm_loop_queue_tm_rsp,
        .aborted_task                   = tcm_loop_aborted_task,
        .fabric_make_wwn                = tcm_loop_make_scsi_hba,
        .fabric_drop_wwn                = tcm_loop_drop_scsi_hba,
        .fabric_make_tpg                = tcm_loop_make_naa_tpg,
        .fabric_drop_tpg                = tcm_loop_drop_naa_tpg,
        .fabric_post_link               = tcm_loop_port_link,
        .fabric_pre_unlink              = tcm_loop_port_unlink,
        .tfc_wwn_attrs                  = tcm_loop_wwn_attrs,
        .tfc_tpg_base_attrs             = tcm_loop_tpg_attrs,
        .tfc_tpg_attrib_attrs           = tcm_loop_tpg_attrib_attrs,
};

static int __init tcm_loop_fabric_init(void)
{
        int ret = -ENOMEM;

        tcm_loop_workqueue = alloc_workqueue("tcm_loop", 0, 0);
        if (!tcm_loop_workqueue)
                goto out;

        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) {
                pr_debug("kmem_cache_create() for tcm_loop_cmd_cache failed\n");
                goto out_destroy_workqueue;
        }

        ret = tcm_loop_alloc_core_bus();
        if (ret)
                goto out_destroy_cache;

        ret = target_register_template(&loop_ops);
        if (ret)
                goto out_release_core_bus;

        return 0;

out_release_core_bus:
        tcm_loop_release_core_bus();
out_destroy_cache:
        kmem_cache_destroy(tcm_loop_cmd_cache);
out_destroy_workqueue:
        destroy_workqueue(tcm_loop_workqueue);
out:
        return ret;
}

static void __exit tcm_loop_fabric_exit(void)
{
        target_unregister_template(&loop_ops);
        tcm_loop_release_core_bus();
        kmem_cache_destroy(tcm_loop_cmd_cache);
        destroy_workqueue(tcm_loop_workqueue);
}

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);