/*
   *  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>
  
  /**

   * bsg_teardown_job - routine to teardown a bsg job

   * @job: 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 = job->req;

  	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)
  {
  	struct request *req = job->req;
  	struct request *rsp = req->next_rq;

  	struct scsi_request *rq = scsi_req(req);

  	int err;

  	err = scsi_req(job->req)->result = result;

  	if (err < 0)
  		/* we're only returning the result field in the reply */

  		rq->sense_len = sizeof(u32);

  	else

  		rq->sense_len = job->reply_len;

  	/* we assume all request payload was transferred, residual == 0 */

  	rq->resid_len = 0;

  
  	if (rsp) {

  		WARN_ON(reply_payload_rcv_len > scsi_req(rsp)->resid_len);

  
  		/* set reply (bidi) residual */

  		scsi_req(rsp)->resid_len -=
  			min(reply_payload_rcv_len, scsi_req(rsp)->resid_len);

  	}
  	blk_complete_request(req);
  }
  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);

  	scsi_req(req)->resid_len = blk_rq_bytes(req);

  	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 int bsg_prepare_job(struct device *dev, struct request *req)

  {
  	struct request *rsp = req->next_rq;

  	struct scsi_request *rq = scsi_req(req);

  	struct bsg_job *job = blk_mq_rq_to_pdu(req);

  	int ret;

  	job->request = rq->cmd;
  	job->request_len = rq->cmd_len;

  	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 0;
  
  failjob_rls_rqst_payload:
  	kfree(job->request_payload.sg_list);
  failjob_rls_job:

  	return -ENOMEM;
  }

  /**
   * 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);

  		ret = bsg_prepare_job(dev, req);

  		if (ret) {

  			scsi_req(req)->result = ret;

  			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);
  }

  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);
  	struct scsi_request *sreq = &job->sreq;

  	/* called right after the request is allocated for the request_queue */
  
  	sreq->sense = kzalloc(SCSI_SENSE_BUFFERSIZE, gfp);
  	if (!sreq->sense)
  		return -ENOMEM;
  
  	return 0;
  }
  
  static void bsg_initialize_rq(struct request *req)
  {
  	struct bsg_job *job = blk_mq_rq_to_pdu(req);
  	struct scsi_request *sreq = &job->sreq;
  	void *sense = sreq->sense;
  
  	/* called right before the request is given to the request_queue user */

  	memset(job, 0, sizeof(*job));
  
  	scsi_req_init(sreq);

  
  	sreq->sense = sense;

  	sreq->sense_len = SCSI_SENSE_BUFFERSIZE;

  
  	job->req = req;

  	job->reply = sense;

  	job->reply_len = sreq->sense_len;
  	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);
  	struct scsi_request *sreq = &job->sreq;
  
  	kfree(sreq->sense);
  }

  /**
   * 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,
  		void (*release)(struct device *))

  {

  	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;
  	queue_flag_set_unlocked(QUEUE_FLAG_BIDI, q);

  	queue_flag_set_unlocked(QUEUE_FLAG_SCSI_PASSTHROUGH, 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, release);

  	if (ret) {
  		printk(KERN_ERR "%s: bsg interface failed to "
  		       "initialize - register queue
  ", 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);