/*******************************************************************************
 * Filename:  target_core_rd.c
 *
 * This file contains the Storage Engine <-> Ramdisk transport
 * specific functions.
 *
 * Copyright (c) 2003, 2004, 2005 PyX Technologies, Inc.
 * Copyright (c) 2005, 2006, 2007 SBE, Inc.
 * Copyright (c) 2007-2010 Rising Tide Systems
 * Copyright (c) 2008-2010 Linux-iSCSI.org
 *
 * Nicholas A. Bellinger <nab@kernel.org>
 *
 * 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.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 *
 ******************************************************************************/

#include <linux/string.h>
#include <linux/parser.h>
#include <linux/timer.h>
#include <linux/blkdev.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <scsi/scsi.h>
#include <scsi/scsi_host.h>

#include <target/target_core_base.h>
#include <target/target_core_backend.h>

#include "target_core_rd.h"

static struct se_subsystem_api rd_mcp_template;

/*      rd_attach_hba(): (Part of se_subsystem_api_t template)
 *
 *
 */
static int rd_attach_hba(struct se_hba *hba, u32 host_id)
{
        struct rd_host *rd_host;

        rd_host = kzalloc(sizeof(struct rd_host), GFP_KERNEL);
        if (!rd_host) {
                pr_err("Unable to allocate memory for struct rd_host\n");
                return -ENOMEM;
        }

        rd_host->rd_host_id = host_id;

        hba->hba_ptr = rd_host;

        pr_debug("CORE_HBA[%d] - TCM Ramdisk HBA Driver %s on"
                " Generic Target Core Stack %s\n", hba->hba_id,
                RD_HBA_VERSION, TARGET_CORE_MOD_VERSION);
        pr_debug("CORE_HBA[%d] - Attached Ramdisk HBA: %u to Generic"
                " MaxSectors: %u\n", hba->hba_id,
                rd_host->rd_host_id, RD_MAX_SECTORS);

        return 0;
}

static void rd_detach_hba(struct se_hba *hba)
{
        struct rd_host *rd_host = hba->hba_ptr;

        pr_debug("CORE_HBA[%d] - Detached Ramdisk HBA: %u from"
                " Generic Target Core\n", hba->hba_id, rd_host->rd_host_id);

        kfree(rd_host);
        hba->hba_ptr = NULL;
}

/*      rd_release_device_space():
 *
 *
 */
static void rd_release_device_space(struct rd_dev *rd_dev)
{
        u32 i, j, page_count = 0, sg_per_table;
        struct rd_dev_sg_table *sg_table;
        struct page *pg;
        struct scatterlist *sg;

        if (!rd_dev->sg_table_array || !rd_dev->sg_table_count)
                return;

        sg_table = rd_dev->sg_table_array;

        for (i = 0; i < rd_dev->sg_table_count; i++) {
                sg = sg_table[i].sg_table;
                sg_per_table = sg_table[i].rd_sg_count;

                for (j = 0; j < sg_per_table; j++) {
                        pg = sg_page(&sg[j]);
                        if (pg) {
                                __free_page(pg);
                                page_count++;
                        }
                }

                kfree(sg);
        }

        pr_debug("CORE_RD[%u] - Released device space for Ramdisk"
                " Device ID: %u, pages %u in %u tables total bytes %lu\n",
                rd_dev->rd_host->rd_host_id, rd_dev->rd_dev_id, page_count,
                rd_dev->sg_table_count, (unsigned long)page_count * PAGE_SIZE);

        kfree(sg_table);
        rd_dev->sg_table_array = NULL;
        rd_dev->sg_table_count = 0;
}


/*      rd_build_device_space():
 *
 *
 */
static int rd_build_device_space(struct rd_dev *rd_dev)
{
        u32 i = 0, j, page_offset = 0, sg_per_table, sg_tables, total_sg_needed;
        u32 max_sg_per_table = (RD_MAX_ALLOCATION_SIZE /
                                sizeof(struct scatterlist));
        struct rd_dev_sg_table *sg_table;
        struct page *pg;
        struct scatterlist *sg;

        if (rd_dev->rd_page_count <= 0) {
                pr_err("Illegal page count: %u for Ramdisk device\n",
                        rd_dev->rd_page_count);
                return -EINVAL;
        }
        total_sg_needed = rd_dev->rd_page_count;

        sg_tables = (total_sg_needed / max_sg_per_table) + 1;

        sg_table = kzalloc(sg_tables * sizeof(struct rd_dev_sg_table), GFP_KERNEL);
        if (!sg_table) {
                pr_err("Unable to allocate memory for Ramdisk"
                        " scatterlist tables\n");
                return -ENOMEM;
        }

        rd_dev->sg_table_array = sg_table;
        rd_dev->sg_table_count = sg_tables;

        while (total_sg_needed) {
                sg_per_table = (total_sg_needed > max_sg_per_table) ?
                        max_sg_per_table : total_sg_needed;

                sg = kzalloc(sg_per_table * sizeof(struct scatterlist),
                                GFP_KERNEL);
                if (!sg) {
                        pr_err("Unable to allocate scatterlist array"
                                " for struct rd_dev\n");
                        return -ENOMEM;
                }

                sg_init_table(sg, sg_per_table);

                sg_table[i].sg_table = sg;
                sg_table[i].rd_sg_count = sg_per_table;
                sg_table[i].page_start_offset = page_offset;
                sg_table[i++].page_end_offset = (page_offset + sg_per_table)
                                                - 1;

                for (j = 0; j < sg_per_table; j++) {
                        pg = alloc_pages(GFP_KERNEL, 0);
                        if (!pg) {
                                pr_err("Unable to allocate scatterlist"
                                        " pages for struct rd_dev_sg_table\n");
                                return -ENOMEM;
                        }
                        sg_assign_page(&sg[j], pg);
                        sg[j].length = PAGE_SIZE;
                }

                page_offset += sg_per_table;
                total_sg_needed -= sg_per_table;
        }

        pr_debug("CORE_RD[%u] - Built Ramdisk Device ID: %u space of"
                " %u pages in %u tables\n", rd_dev->rd_host->rd_host_id,
                rd_dev->rd_dev_id, rd_dev->rd_page_count,
                rd_dev->sg_table_count);

        return 0;
}

static void *rd_allocate_virtdevice(
        struct se_hba *hba,
        const char *name,
        int rd_direct)
{
        struct rd_dev *rd_dev;
        struct rd_host *rd_host = hba->hba_ptr;

        rd_dev = kzalloc(sizeof(struct rd_dev), GFP_KERNEL);
        if (!rd_dev) {
                pr_err("Unable to allocate memory for struct rd_dev\n");
                return NULL;
        }

        rd_dev->rd_host = rd_host;
        rd_dev->rd_direct = rd_direct;

        return rd_dev;
}

static void *rd_MEMCPY_allocate_virtdevice(struct se_hba *hba, const char *name)
{
        return rd_allocate_virtdevice(hba, name, 0);
}

/*      rd_create_virtdevice():
 *
 *
 */
static struct se_device *rd_create_virtdevice(
        struct se_hba *hba,
        struct se_subsystem_dev *se_dev,
        void *p,
        int rd_direct)
{
        struct se_device *dev;
        struct se_dev_limits dev_limits;
        struct rd_dev *rd_dev = p;
        struct rd_host *rd_host = hba->hba_ptr;
        int dev_flags = 0, ret;
        char prod[16], rev[4];

        memset(&dev_limits, 0, sizeof(struct se_dev_limits));

        ret = rd_build_device_space(rd_dev);
        if (ret < 0)
                goto fail;

        snprintf(prod, 16, "RAMDISK-%s", (rd_dev->rd_direct) ? "DR" : "MCP");
        snprintf(rev, 4, "%s", (rd_dev->rd_direct) ? RD_DR_VERSION :
                                                RD_MCP_VERSION);

        dev_limits.limits.logical_block_size = RD_BLOCKSIZE;
        dev_limits.limits.max_hw_sectors = RD_MAX_SECTORS;
        dev_limits.limits.max_sectors = RD_MAX_SECTORS;
        dev_limits.hw_queue_depth = RD_MAX_DEVICE_QUEUE_DEPTH;
        dev_limits.queue_depth = RD_DEVICE_QUEUE_DEPTH;

        dev = transport_add_device_to_core_hba(hba,
                        &rd_mcp_template, se_dev, dev_flags, rd_dev,
                        &dev_limits, prod, rev);
        if (!dev)
                goto fail;

        rd_dev->rd_dev_id = rd_host->rd_host_dev_id_count++;
        rd_dev->rd_queue_depth = dev->queue_depth;

        pr_debug("CORE_RD[%u] - Added TCM %s Ramdisk Device ID: %u of"
                " %u pages in %u tables, %lu total bytes\n",
                rd_host->rd_host_id, (!rd_dev->rd_direct) ? "MEMCPY" :
                "DIRECT", rd_dev->rd_dev_id, rd_dev->rd_page_count,
                rd_dev->sg_table_count,
                (unsigned long)(rd_dev->rd_page_count * PAGE_SIZE));

        return dev;

fail:
        rd_release_device_space(rd_dev);
        return ERR_PTR(ret);
}

static struct se_device *rd_MEMCPY_create_virtdevice(
        struct se_hba *hba,
        struct se_subsystem_dev *se_dev,
        void *p)
{
        return rd_create_virtdevice(hba, se_dev, p, 0);
}

/*      rd_free_device(): (Part of se_subsystem_api_t template)
 *
 *
 */
static void rd_free_device(void *p)
{
        struct rd_dev *rd_dev = p;

        rd_release_device_space(rd_dev);
        kfree(rd_dev);
}

static inline struct rd_request *RD_REQ(struct se_task *task)
{
        return container_of(task, struct rd_request, rd_task);
}

static struct se_task *
rd_alloc_task(unsigned char *cdb)
{
        struct rd_request *rd_req;

        rd_req = kzalloc(sizeof(struct rd_request), GFP_KERNEL);
        if (!rd_req) {
                pr_err("Unable to allocate struct rd_request\n");
                return NULL;
        }

        return &rd_req->rd_task;
}

/*      rd_get_sg_table():
 *
 *
 */
static struct rd_dev_sg_table *rd_get_sg_table(struct rd_dev *rd_dev, u32 page)
{
        u32 i;
        struct rd_dev_sg_table *sg_table;

        for (i = 0; i < rd_dev->sg_table_count; i++) {
                sg_table = &rd_dev->sg_table_array[i];
                if ((sg_table->page_start_offset <= page) &&
                    (sg_table->page_end_offset >= page))
                        return sg_table;
        }

        pr_err("Unable to locate struct rd_dev_sg_table for page: %u\n",
                        page);

        return NULL;
}

static int rd_MEMCPY(struct rd_request *req, u32 read_rd)
{
        struct se_task *task = &req->rd_task;
        struct rd_dev *dev = req->rd_task.task_se_cmd->se_dev->dev_ptr;
        struct rd_dev_sg_table *table;
        struct scatterlist *rd_sg;
        struct sg_mapping_iter m;
        u32 rd_offset = req->rd_offset;
        u32 src_len;

        table = rd_get_sg_table(dev, req->rd_page);
        if (!table)
                return -EINVAL;

        rd_sg = &table->sg_table[req->rd_page - table->page_start_offset];

        pr_debug("RD[%u]: %s LBA: %llu, Size: %u Page: %u, Offset: %u\n",
                        dev->rd_dev_id, read_rd ? "Read" : "Write",
                        task->task_lba, req->rd_size, req->rd_page,
                        rd_offset);

        src_len = PAGE_SIZE - rd_offset;
        sg_miter_start(&m, task->task_sg, task->task_sg_nents,
                        read_rd ? SG_MITER_TO_SG : SG_MITER_FROM_SG);
        while (req->rd_size) {
                u32 len;
                void *rd_addr;

                sg_miter_next(&m);
                len = min((u32)m.length, src_len);
                m.consumed = len;

                rd_addr = sg_virt(rd_sg) + rd_offset;

                if (read_rd)
                        memcpy(m.addr, rd_addr, len);
                else
                        memcpy(rd_addr, m.addr, len);

                req->rd_size -= len;
                if (!req->rd_size)
                        continue;

                src_len -= len;
                if (src_len) {
                        rd_offset += len;
                        continue;
                }

                /* rd page completed, next one please */
                req->rd_page++;
                rd_offset = 0;
                src_len = PAGE_SIZE;
                if (req->rd_page <= table->page_end_offset) {
                        rd_sg++;
                        continue;
                }

                table = rd_get_sg_table(dev, req->rd_page);
                if (!table) {
                        sg_miter_stop(&m);
                        return -EINVAL;
                }

                /* since we increment, the first sg entry is correct */
                rd_sg = table->sg_table;
        }
        sg_miter_stop(&m);
        return 0;
}

/*      rd_MEMCPY_do_task(): (Part of se_subsystem_api_t template)
 *
 *
 */
static int rd_MEMCPY_do_task(struct se_task *task)
{
        struct se_device *dev = task->task_se_cmd->se_dev;
        struct rd_request *req = RD_REQ(task);
        u64 tmp;
        int ret;

        tmp = task->task_lba * dev->se_sub_dev->se_dev_attrib.block_size;
        req->rd_offset = do_div(tmp, PAGE_SIZE);
        req->rd_page = tmp;
        req->rd_size = task->task_size;

        ret = rd_MEMCPY(req, task->task_data_direction == DMA_FROM_DEVICE);
        if (ret != 0)
                return ret;

        task->task_scsi_status = GOOD;
        transport_complete_task(task, 1);
        return 0;
}

/*      rd_free_task(): (Part of se_subsystem_api_t template)
 *
 *
 */
static void rd_free_task(struct se_task *task)
{
        kfree(RD_REQ(task));
}

enum {
        Opt_rd_pages, Opt_err
};

static match_table_t tokens = {
        {Opt_rd_pages, "rd_pages=%d"},
        {Opt_err, NULL}
};

static ssize_t rd_set_configfs_dev_params(
        struct se_hba *hba,
        struct se_subsystem_dev *se_dev,
        const char *page,
        ssize_t count)
{
        struct rd_dev *rd_dev = se_dev->se_dev_su_ptr;
        char *orig, *ptr, *opts;
        substring_t args[MAX_OPT_ARGS];
        int ret = 0, arg, token;

        opts = kstrdup(page, GFP_KERNEL);
        if (!opts)
                return -ENOMEM;

        orig = opts;

        while ((ptr = strsep(&opts, ",\n")) != NULL) {
                if (!*ptr)
                        continue;

                token = match_token(ptr, tokens, args);
                switch (token) {
                case Opt_rd_pages:
                        match_int(args, &arg);
                        rd_dev->rd_page_count = arg;
                        pr_debug("RAMDISK: Referencing Page"
                                " Count: %u\n", rd_dev->rd_page_count);
                        rd_dev->rd_flags |= RDF_HAS_PAGE_COUNT;
                        break;
                default:
                        break;
                }
        }

        kfree(orig);
        return (!ret) ? count : ret;
}

static ssize_t rd_check_configfs_dev_params(struct se_hba *hba, struct se_subsystem_dev *se_dev)
{
        struct rd_dev *rd_dev = se_dev->se_dev_su_ptr;

        if (!(rd_dev->rd_flags & RDF_HAS_PAGE_COUNT)) {
                pr_debug("Missing rd_pages= parameter\n");
                return -EINVAL;
        }

        return 0;
}

static ssize_t rd_show_configfs_dev_params(
        struct se_hba *hba,
        struct se_subsystem_dev *se_dev,
        char *b)
{
        struct rd_dev *rd_dev = se_dev->se_dev_su_ptr;
        ssize_t bl = sprintf(b, "TCM RamDisk ID: %u  RamDisk Makeup: %s\n",
                        rd_dev->rd_dev_id, (rd_dev->rd_direct) ?
                        "rd_direct" : "rd_mcp");
        bl += sprintf(b + bl, "        PAGES/PAGE_SIZE: %u*%lu"
                        "  SG_table_count: %u\n", rd_dev->rd_page_count,
                        PAGE_SIZE, rd_dev->sg_table_count);
        return bl;
}

static u32 rd_get_device_rev(struct se_device *dev)
{
        return SCSI_SPC_2; /* Returns SPC-3 in Initiator Data */
}

static u32 rd_get_device_type(struct se_device *dev)
{
        return TYPE_DISK;
}

static sector_t rd_get_blocks(struct se_device *dev)
{
        struct rd_dev *rd_dev = dev->dev_ptr;
        unsigned long long blocks_long = ((rd_dev->rd_page_count * PAGE_SIZE) /
                        dev->se_sub_dev->se_dev_attrib.block_size) - 1;

        return blocks_long;
}

static struct se_subsystem_api rd_mcp_template = {
        .name                   = "rd_mcp",
        .transport_type         = TRANSPORT_PLUGIN_VHBA_VDEV,
        .attach_hba             = rd_attach_hba,
        .detach_hba             = rd_detach_hba,
        .allocate_virtdevice    = rd_MEMCPY_allocate_virtdevice,
        .create_virtdevice      = rd_MEMCPY_create_virtdevice,
        .free_device            = rd_free_device,
        .alloc_task             = rd_alloc_task,
        .do_task                = rd_MEMCPY_do_task,
        .free_task              = rd_free_task,
        .check_configfs_dev_params = rd_check_configfs_dev_params,
        .set_configfs_dev_params = rd_set_configfs_dev_params,
        .show_configfs_dev_params = rd_show_configfs_dev_params,
        .get_device_rev         = rd_get_device_rev,
        .get_device_type        = rd_get_device_type,
        .get_blocks             = rd_get_blocks,
};

int __init rd_module_init(void)
{
        int ret;

        ret = transport_subsystem_register(&rd_mcp_template);
        if (ret < 0) {
                return ret;
        }

        return 0;
}

void rd_module_exit(void)
{
        transport_subsystem_release(&rd_mcp_template);
}