/*
   *  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_destroy_job - routine to teardown/delete a bsg job
   * @job: bsg_job that is to be torn down
   */
  static void bsg_destroy_job(struct bsg_job *job)
  {
  	put_device(job->dev);	/* release reference for the request */
  
  	kfree(job->request_payload.sg_list);
  	kfree(job->reply_payload.sg_list);
  	kfree(job);
  }
  
  /**
   * 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;
  	int err;
  
  	err = job->req->errors = result;
  	if (err < 0)
  		/* we're only returning the result field in the reply */
  		job->req->sense_len = sizeof(u32);
  	else
  		job->req->sense_len = job->reply_len;
  	/* we assume all request payload was transferred, residual == 0 */
  	req->resid_len = 0;
  
  	if (rsp) {
  		WARN_ON(reply_payload_rcv_len > rsp->resid_len);
  
  		/* set reply (bidi) residual */
  		rsp->resid_len -= min(reply_payload_rcv_len, 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 = rq->special;
  
  	blk_end_request_all(rq, rq->errors);
  	bsg_destroy_job(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_create_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_create_job(struct device *dev, struct request *req)
  {
  	struct request *rsp = req->next_rq;
  	struct request_queue *q = req->q;
  	struct bsg_job *job;
  	int ret;
  
  	BUG_ON(req->special);
  
  	job = kzalloc(sizeof(struct bsg_job) + q->bsg_job_size, GFP_KERNEL);
  	if (!job)
  		return -ENOMEM;
  
  	req->special = job;
  	job->req = req;
  	if (q->bsg_job_size)
  		job->dd_data = (void *)&job[1];
  	job->request = req->cmd;
  	job->request_len = req->cmd_len;
  	job->reply = req->sense;
  	job->reply_len = SCSI_SENSE_BUFFERSIZE;	/* Size of sense buffer
  						 * allocated */
  	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);
  	return 0;
  
  failjob_rls_rqst_payload:
  	kfree(job->request_payload.sg_list);
  failjob_rls_job:
  	kfree(job);
  	return -ENOMEM;
  }
  
  /*
   * bsg_goose_queue - restart queue in case it was stopped
   * @q: request q to be restarted
   */
  void bsg_goose_queue(struct request_queue *q)
  {
  	if (!q)
  		return;
  
  	blk_run_queue_async(q);
  }
  EXPORT_SYMBOL_GPL(bsg_goose_queue);
  
  /**
   * 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 the req->errors.
   *
   * Drivers/subsys should pass this to the queue init function.
   */
  void bsg_request_fn(struct request_queue *q)
  {
  	struct device *dev = q->queuedata;
  	struct request *req;
  	struct bsg_job *job;
  	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_create_job(dev, req);
  		if (ret) {
  			req->errors = ret;
  			blk_end_request_all(req, ret);
  			spin_lock_irq(q->queue_lock);
  			continue;
  		}
  
  		job = req->special;
  		ret = q->bsg_job_fn(job);
  		spin_lock_irq(q->queue_lock);
  		if (ret)
  			break;
  	}
  
  	spin_unlock_irq(q->queue_lock);
  	put_device(dev);
  	spin_lock_irq(q->queue_lock);
  }
  EXPORT_SYMBOL_GPL(bsg_request_fn);
  
  /**
   * bsg_setup_queue - Create and add the bsg hooks so we can receive requests
   * @dev: device to attach bsg device to
   * @q: request queue setup by caller
   * @name: device to give bsg device
   * @job_fn: bsg job handler
   * @dd_job_size: size of LLD data needed for each job
   *
   * The caller should have setup the reuqest queue with bsg_request_fn
   * as the request_fn.
   */
  int bsg_setup_queue(struct device *dev, struct request_queue *q,
  		    char *name, bsg_job_fn *job_fn, int dd_job_size)
  {
  	int ret;
  
  	q->queuedata = dev;
  	q->bsg_job_size = dd_job_size;
  	q->bsg_job_fn = job_fn;
  	queue_flag_set_unlocked(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, NULL);
  	if (ret) {
  		printk(KERN_ERR "%s: bsg interface failed to "
  		       "initialize - register queue
  ", dev->kobj.name);
  		return ret;
  	}
  
  	return 0;
  }
  EXPORT_SYMBOL_GPL(bsg_setup_queue);
  
  /**
   * bsg_remove_queue - Deletes the bsg dev from the q
   * @q:	the request_queue that is to be torn down.
   *
   * Notes:
   *   Before unregistering the queue empty any requests that are blocked
   */
  void bsg_remove_queue(struct request_queue *q)
  {
  	struct request *req; /* block request */
  	int counts; /* totals for request_list count and starved */
  
  	if (!q)
  		return;
  
  	/* Stop taking in new requests */
  	spin_lock_irq(q->queue_lock);
  	blk_stop_queue(q);
  
  	/* drain all requests in the queue */
  	while (1) {
  		/* need the lock to fetch a request
  		 * this may fetch the same reqeust as the previous pass
  		 */
  		req = blk_fetch_request(q);
  		/* save requests in use and starved */
  		counts = q->rq.count[0] + q->rq.count[1] +
  			 q->rq.starved[0] + q->rq.starved[1];
  		spin_unlock_irq(q->queue_lock);
  		/* any requests still outstanding? */
  		if (counts == 0)
  			break;
  
  		/* This may be the same req as the previous iteration,
  		 * always send the blk_end_request_all after a prefetch.
  		 * It is not okay to not end the request because the
  		 * prefetch started the request.
  		 */
  		if (req) {
  			/* return -ENXIO to indicate that this queue is
  			 * going away
  			 */
  			req->errors = -ENXIO;
  			blk_end_request_all(req, -ENXIO);
  		}
  
  		msleep(200); /* allow bsg to possibly finish */
  		spin_lock_irq(q->queue_lock);
  	}
  	bsg_unregister_queue(q);
  }
  EXPORT_SYMBOL_GPL(bsg_remove_queue);