// SPDX-License-Identifier: GPL-2.0-or-later

#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_remote.h"

static inline struct tcm_remote_tpg *remote_tpg(struct se_portal_group *se_tpg)
{
        return container_of(se_tpg, struct tcm_remote_tpg, remote_se_tpg);
}

static char *tcm_remote_get_endpoint_wwn(struct se_portal_group *se_tpg)
{
        /*
         * Return the passed NAA identifier for the Target Port
         */
        return &remote_tpg(se_tpg)->remote_hba->remote_wwn_address[0];
}

static u16 tcm_remote_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 remote_tpg(se_tpg)->remote_tpgt;
}

static int tcm_remote_dummy_cmd_fn(struct se_cmd *se_cmd)
{
        return 0;
}

static void tcm_remote_dummy_cmd_void_fn(struct se_cmd *se_cmd)
{

}

static char *tcm_remote_dump_proto_id(struct tcm_remote_hba *remote_hba)
{
        switch (remote_hba->remote_proto_id) {
        case SCSI_PROTOCOL_SAS:
                return "SAS";
        case SCSI_PROTOCOL_SRP:
                return "SRP";
        case SCSI_PROTOCOL_FCP:
                return "FCP";
        case SCSI_PROTOCOL_ISCSI:
                return "iSCSI";
        default:
                break;
        }

        return "Unknown";
}

static int tcm_remote_port_link(
        struct se_portal_group *se_tpg,
        struct se_lun *lun)
{
        pr_debug("TCM_Remote_ConfigFS: Port Link LUN %lld Successful\n",
                 lun->unpacked_lun);
        return 0;
}

static void tcm_remote_port_unlink(
        struct se_portal_group *se_tpg,
        struct se_lun *lun)
{
        pr_debug("TCM_Remote_ConfigFS: Port Unlink LUN %lld Successful\n",
                 lun->unpacked_lun);
}

static struct se_portal_group *tcm_remote_make_tpg(
        struct se_wwn *wwn,
        const char *name)
{
        struct tcm_remote_hba *remote_hba = container_of(wwn,
                        struct tcm_remote_hba, remote_hba_wwn);
        struct tcm_remote_tpg *remote_tpg;
        unsigned long tpgt;
        int ret;

        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);
        }
        remote_tpg = &remote_hba->remote_hba_tpgs[tpgt];
        remote_tpg->remote_hba = remote_hba;
        remote_tpg->remote_tpgt = tpgt;
        /*
         * Register the remote_tpg as a emulated TCM Target Endpoint
         */
        ret = core_tpg_register(wwn, &remote_tpg->remote_se_tpg,
                                remote_hba->remote_proto_id);
        if (ret < 0)
                return ERR_PTR(-ENOMEM);

        pr_debug("TCM_Remote_ConfigFS: Allocated Emulated %s Target Port %s,t,0x%04lx\n",
                 tcm_remote_dump_proto_id(remote_hba),
                 config_item_name(&wwn->wwn_group.cg_item), tpgt);
        return &remote_tpg->remote_se_tpg;
}

static void tcm_remote_drop_tpg(struct se_portal_group *se_tpg)
{
        struct se_wwn *wwn = se_tpg->se_tpg_wwn;
        struct tcm_remote_tpg *remote_tpg = container_of(se_tpg,
                                struct tcm_remote_tpg, remote_se_tpg);
        struct tcm_remote_hba *remote_hba;
        unsigned short tpgt;

        remote_hba = remote_tpg->remote_hba;
        tpgt = remote_tpg->remote_tpgt;

        /*
         * Deregister the remote_tpg as a emulated TCM Target Endpoint
         */
        core_tpg_deregister(se_tpg);

        remote_tpg->remote_hba = NULL;
        remote_tpg->remote_tpgt = 0;

        pr_debug("TCM_Remote_ConfigFS: Deallocated Emulated %s Target Port %s,t,0x%04x\n",
                 tcm_remote_dump_proto_id(remote_hba),
                 config_item_name(&wwn->wwn_group.cg_item), tpgt);
}

static struct se_wwn *tcm_remote_make_wwn(
        struct target_fabric_configfs *tf,
        struct config_group *group,
        const char *name)
{
        struct tcm_remote_hba *remote_hba;
        char *ptr;
        int ret, off = 0;

        remote_hba = kzalloc_obj(*remote_hba);
        if (!remote_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) {
                remote_hba->remote_proto_id = SCSI_PROTOCOL_SAS;
                goto check_len;
        }
        ptr = strstr(name, "fc.");
        if (ptr) {
                remote_hba->remote_proto_id = SCSI_PROTOCOL_FCP;
                off = 3; /* Skip over "fc." */
                goto check_len;
        }
        ptr = strstr(name, "0x");
        if (ptr) {
                remote_hba->remote_proto_id = SCSI_PROTOCOL_SRP;
                off = 2; /* Skip over "0x" */
                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;
        }
        remote_hba->remote_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_remote_dump_proto_id(remote_hba), TL_WWN_ADDR_LEN);
                ret = -EINVAL;
                goto out;
        }
        snprintf(&remote_hba->remote_wwn_address[0], TL_WWN_ADDR_LEN, "%s", &name[off]);

        pr_debug("TCM_Remote_ConfigFS: Allocated emulated Target %s Address: %s\n",
                 tcm_remote_dump_proto_id(remote_hba), name);
        return &remote_hba->remote_hba_wwn;
out:
        kfree(remote_hba);
        return ERR_PTR(ret);
}

static void tcm_remote_drop_wwn(struct se_wwn *wwn)
{
        struct tcm_remote_hba *remote_hba = container_of(wwn,
                                struct tcm_remote_hba, remote_hba_wwn);

        pr_debug("TCM_Remote_ConfigFS: Deallocating emulated Target %s Address: %s\n",
                 tcm_remote_dump_proto_id(remote_hba),
                 remote_hba->remote_wwn_address);
        kfree(remote_hba);
}

static ssize_t tcm_remote_wwn_version_show(struct config_item *item, char *page)
{
        return sprintf(page, "TCM Remote Fabric module %s\n", TCM_REMOTE_VERSION);
}

CONFIGFS_ATTR_RO(tcm_remote_wwn_, version);

static struct configfs_attribute *tcm_remote_wwn_attrs[] = {
        &tcm_remote_wwn_attr_version,
        NULL,
};

static const struct target_core_fabric_ops remote_ops = {
        .module                         = THIS_MODULE,
        .fabric_name                    = "remote",
        .tpg_get_wwn                    = tcm_remote_get_endpoint_wwn,
        .tpg_get_tag                    = tcm_remote_get_tag,
        .check_stop_free                = tcm_remote_dummy_cmd_fn,
        .release_cmd                    = tcm_remote_dummy_cmd_void_fn,
        .write_pending                  = tcm_remote_dummy_cmd_fn,
        .queue_data_in                  = tcm_remote_dummy_cmd_fn,
        .queue_status                   = tcm_remote_dummy_cmd_fn,
        .queue_tm_rsp                   = tcm_remote_dummy_cmd_void_fn,
        .aborted_task                   = tcm_remote_dummy_cmd_void_fn,
        .fabric_make_wwn                = tcm_remote_make_wwn,
        .fabric_drop_wwn                = tcm_remote_drop_wwn,
        .fabric_make_tpg                = tcm_remote_make_tpg,
        .fabric_drop_tpg                = tcm_remote_drop_tpg,
        .fabric_post_link               = tcm_remote_port_link,
        .fabric_pre_unlink              = tcm_remote_port_unlink,
        .tfc_wwn_attrs                  = tcm_remote_wwn_attrs,
};

static int __init tcm_remote_fabric_init(void)
{
        return target_register_template(&remote_ops);
}

static void __exit tcm_remote_fabric_exit(void)
{
        target_unregister_template(&remote_ops);
}

MODULE_DESCRIPTION("TCM virtual remote target");
MODULE_AUTHOR("Dmitry Bogdanov <d.bogdanov@yadro.com>");
MODULE_LICENSE("GPL");
module_init(tcm_remote_fabric_init);
module_exit(tcm_remote_fabric_exit);