/*
 *  BSG helper library
 *
 *  Copyright (C) 2008   James Smart, Emulex Corporation
 *  Copyright (C) 2011   Red Hat, Inc.  All rights reserved.
 *  Copyright (C) 2011   Mike Christie
 *
 *  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/slab.h>
#include <linux/blkdev.h>
#include <linux/delay.h>
#include <linux/scatterlist.h>
#include <linux/bsg-lib.h>
#include <linux/export.h>
#include <scsi/scsi_cmnd.h>
#include <scsi/sg.h>

#define uptr64(val) ((void __user *)(uintptr_t)(val))

static int bsg_transport_check_proto(struct sg_io_v4 *hdr)
{
        if (hdr->protocol != BSG_PROTOCOL_SCSI  ||
            hdr->subprotocol != BSG_SUB_PROTOCOL_SCSI_TRANSPORT)
                return -EINVAL;
        if (!capable(CAP_SYS_RAWIO))
                return -EPERM;
        return 0;
}

static int bsg_transport_fill_hdr(struct request *rq, struct sg_io_v4 *hdr,
                fmode_t mode)
{
        struct bsg_job *job = blk_mq_rq_to_pdu(rq);

        job->request_len = hdr->request_len;
        job->request = memdup_user(uptr64(hdr->request), hdr->request_len);

        return PTR_ERR_OR_ZERO(job->request);
}

static int bsg_transport_complete_rq(struct request *rq, struct sg_io_v4 *hdr)
{
        struct bsg_job *job = blk_mq_rq_to_pdu(rq);
        int ret = 0;

        /*
         * The assignments below don't make much sense, but are kept for
         * bug by bug backwards compatibility:
         */
        hdr->device_status = job->result & 0xff;
        hdr->transport_status = host_byte(job->result);
        hdr->driver_status = driver_byte(job->result);
        hdr->info = 0;
        if (hdr->device_status || hdr->transport_status || hdr->driver_status)
                hdr->info |= SG_INFO_CHECK;
        hdr->response_len = 0;

        if (job->result < 0) {
                /* we're only returning the result field in the reply */
                job->reply_len = sizeof(u32);
                ret = job->result;
        }

        if (job->reply_len && hdr->response) {
                int len = min(hdr->max_response_len, job->reply_len);

                if (copy_to_user(uptr64(hdr->response), job->reply, len))
                        ret = -EFAULT;
                else
                        hdr->response_len = len;
        }

        /* we assume all request payload was transferred, residual == 0 */
        hdr->dout_resid = 0;

        if (rq->next_rq) {
                unsigned int rsp_len = job->reply_payload.payload_len;

                if (WARN_ON(job->reply_payload_rcv_len > rsp_len))
                        hdr->din_resid = 0;
                else
                        hdr->din_resid = rsp_len - job->reply_payload_rcv_len;
        } else {
                hdr->din_resid = 0;
        }

        return ret;
}

static void bsg_transport_free_rq(struct request *rq)
{
        struct bsg_job *job = blk_mq_rq_to_pdu(rq);

        kfree(job->request);
}

static const struct bsg_ops bsg_transport_ops = {
        .check_proto            = bsg_transport_check_proto,
        .fill_hdr               = bsg_transport_fill_hdr,
        .complete_rq            = bsg_transport_complete_rq,
        .free_rq                = bsg_transport_free_rq,
};

/**
 * bsg_teardown_job - routine to teardown a bsg job
 * @kref: kref inside bsg_job that is to be torn down
 */
static void bsg_teardown_job(struct kref *kref)
{
        struct bsg_job *job = container_of(kref, struct bsg_job, kref);
        struct request *rq = blk_mq_rq_from_pdu(job);

        put_device(job->dev);   /* release reference for the request */

        kfree(job->request_payload.sg_list);
        kfree(job->reply_payload.sg_list);

        blk_end_request_all(rq, BLK_STS_OK);
}

void bsg_job_put(struct bsg_job *job)
{
        kref_put(&job->kref, bsg_teardown_job);
}
EXPORT_SYMBOL_GPL(bsg_job_put);

int bsg_job_get(struct bsg_job *job)
{
        return kref_get_unless_zero(&job->kref);
}
EXPORT_SYMBOL_GPL(bsg_job_get);

/**
 * bsg_job_done - completion routine for bsg requests
 * @job: bsg_job that is complete
 * @result: job reply result
 * @reply_payload_rcv_len: length of payload recvd
 *
 * The LLD should call this when the bsg job has completed.
 */
void bsg_job_done(struct bsg_job *job, int result,
                  unsigned int reply_payload_rcv_len)
{
        job->result = result;
        job->reply_payload_rcv_len = reply_payload_rcv_len;
        blk_complete_request(blk_mq_rq_from_pdu(job));
}
EXPORT_SYMBOL_GPL(bsg_job_done);

/**
 * bsg_softirq_done - softirq done routine for destroying the bsg requests
 * @rq: BSG request that holds the job to be destroyed
 */
static void bsg_softirq_done(struct request *rq)
{
        struct bsg_job *job = blk_mq_rq_to_pdu(rq);

        bsg_job_put(job);
}

static int bsg_map_buffer(struct bsg_buffer *buf, struct request *req)
{
        size_t sz = (sizeof(struct scatterlist) * req->nr_phys_segments);

        BUG_ON(!req->nr_phys_segments);

        buf->sg_list = kzalloc(sz, GFP_KERNEL);
        if (!buf->sg_list)
                return -ENOMEM;
        sg_init_table(buf->sg_list, req->nr_phys_segments);
        buf->sg_cnt = blk_rq_map_sg(req->q, req, buf->sg_list);
        buf->payload_len = blk_rq_bytes(req);
        return 0;
}

/**
 * bsg_prepare_job - create the bsg_job structure for the bsg request
 * @dev: device that is being sent the bsg request
 * @req: BSG request that needs a job structure
 */
static bool bsg_prepare_job(struct device *dev, struct request *req)
{
        struct request *rsp = req->next_rq;
        struct bsg_job *job = blk_mq_rq_to_pdu(req);
        int ret;

        job->timeout = req->timeout;

        if (req->bio) {
                ret = bsg_map_buffer(&job->request_payload, req);
                if (ret)
                        goto failjob_rls_job;
        }
        if (rsp && rsp->bio) {
                ret = bsg_map_buffer(&job->reply_payload, rsp);
                if (ret)
                        goto failjob_rls_rqst_payload;
        }
        job->dev = dev;
        /* take a reference for the request */
        get_device(job->dev);
        kref_init(&job->kref);
        return true;

failjob_rls_rqst_payload:
        kfree(job->request_payload.sg_list);
failjob_rls_job:
        job->result = -ENOMEM;
        return false;
}

/**
 * bsg_request_fn - generic handler for bsg requests
 * @q: request queue to manage
 *
 * On error the create_bsg_job function should return a -Exyz error value
 * that will be set to ->result.
 *
 * Drivers/subsys should pass this to the queue init function.
 */
static void bsg_request_fn(struct request_queue *q)
        __releases(q->queue_lock)
        __acquires(q->queue_lock)
{
        struct device *dev = q->queuedata;
        struct request *req;
        int ret;

        if (!get_device(dev))
                return;

        while (1) {
                req = blk_fetch_request(q);
                if (!req)
                        break;
                spin_unlock_irq(q->queue_lock);

                if (!bsg_prepare_job(dev, req)) {
                        blk_end_request_all(req, BLK_STS_OK);
                        spin_lock_irq(q->queue_lock);
                        continue;
                }

                ret = q->bsg_job_fn(blk_mq_rq_to_pdu(req));
                spin_lock_irq(q->queue_lock);
                if (ret)
                        break;
        }

        spin_unlock_irq(q->queue_lock);
        put_device(dev);
        spin_lock_irq(q->queue_lock);
}

/* called right after the request is allocated for the request_queue */
static int bsg_init_rq(struct request_queue *q, struct request *req, gfp_t gfp)
{
        struct bsg_job *job = blk_mq_rq_to_pdu(req);

        job->reply = kzalloc(SCSI_SENSE_BUFFERSIZE, gfp);
        if (!job->reply)
                return -ENOMEM;
        return 0;
}

/* called right before the request is given to the request_queue user */
static void bsg_initialize_rq(struct request *req)
{
        struct bsg_job *job = blk_mq_rq_to_pdu(req);
        void *reply = job->reply;

        memset(job, 0, sizeof(*job));
        job->reply = reply;
        job->reply_len = SCSI_SENSE_BUFFERSIZE;
        job->dd_data = job + 1;
}

static void bsg_exit_rq(struct request_queue *q, struct request *req)
{
        struct bsg_job *job = blk_mq_rq_to_pdu(req);

        kfree(job->reply);
}

/**
 * bsg_setup_queue - Create and add the bsg hooks so we can receive requests
 * @dev: device to attach bsg device to
 * @name: device to give bsg device
 * @job_fn: bsg job handler
 * @dd_job_size: size of LLD data needed for each job
 */
struct request_queue *bsg_setup_queue(struct device *dev, const char *name,
                bsg_job_fn *job_fn, int dd_job_size)
{
        struct request_queue *q;
        int ret;

        q = blk_alloc_queue(GFP_KERNEL);
        if (!q)
                return ERR_PTR(-ENOMEM);
        q->cmd_size = sizeof(struct bsg_job) + dd_job_size;
        q->init_rq_fn = bsg_init_rq;
        q->exit_rq_fn = bsg_exit_rq;
        q->initialize_rq_fn = bsg_initialize_rq;
        q->request_fn = bsg_request_fn;

        ret = blk_init_allocated_queue(q);
        if (ret)
                goto out_cleanup_queue;

        q->queuedata = dev;
        q->bsg_job_fn = job_fn;
        blk_queue_flag_set(QUEUE_FLAG_BIDI, q);
        blk_queue_softirq_done(q, bsg_softirq_done);
        blk_queue_rq_timeout(q, BLK_DEFAULT_SG_TIMEOUT);

        ret = bsg_register_queue(q, dev, name, &bsg_transport_ops);
        if (ret) {
                printk(KERN_ERR "%s: bsg interface failed to "
                       "initialize - register queue\n", dev->kobj.name);
                goto out_cleanup_queue;
        }

        return q;
out_cleanup_queue:
        blk_cleanup_queue(q);
        return ERR_PTR(ret);
}
EXPORT_SYMBOL_GPL(bsg_setup_queue);