// SPDX-License-Identifier: GPL-2.0

  /*

   * bsg.c - block layer implementation of the sg v4 interface

   */

  #include <linux/module.h>
  #include <linux/init.h>
  #include <linux/file.h>
  #include <linux/blkdev.h>

  #include <linux/cdev.h>

  #include <linux/jiffies.h>

  #include <linux/percpu.h>

  #include <linux/idr.h>

  #include <linux/bsg.h>

  #include <linux/slab.h>

  
  #include <scsi/scsi.h>
  #include <scsi/scsi_ioctl.h>
  #include <scsi/scsi_cmnd.h>

  #include <scsi/scsi_device.h>
  #include <scsi/scsi_driver.h>

  #include <scsi/sg.h>

  #define BSG_DESCRIPTION	"Block layer SCSI generic (bsg) driver"
  #define BSG_VERSION	"0.4"

  #define bsg_dbg(bd, fmt, ...) \
  	pr_debug("%s: " fmt, (bd)->name, ##__VA_ARGS__)

  struct bsg_device {

  	struct request_queue *queue;

  	spinlock_t lock;

  	struct hlist_node dev_list;

  	refcount_t ref_count;

  	char name[20];

  	int max_queue;

  };

  #define BSG_DEFAULT_CMDS	64

  #define BSG_MAX_DEVS		32768

  static DEFINE_MUTEX(bsg_mutex);

  static DEFINE_IDR(bsg_minor_idr);

  #define BSG_LIST_ARRAY_SIZE	8

  static struct hlist_head bsg_device_list[BSG_LIST_ARRAY_SIZE];

  
  static struct class *bsg_class;

  static int bsg_major;

  static inline struct hlist_head *bsg_dev_idx_hash(int index)

  {

  	return &bsg_device_list[index & (BSG_LIST_ARRAY_SIZE - 1)];

  }

  #define uptr64(val) ((void __user *)(uintptr_t)(val))
  
  static int bsg_scsi_check_proto(struct sg_io_v4 *hdr)
  {
  	if (hdr->protocol != BSG_PROTOCOL_SCSI  ||
  	    hdr->subprotocol != BSG_SUB_PROTOCOL_SCSI_CMD)
  		return -EINVAL;
  	return 0;
  }
  
  static int bsg_scsi_fill_hdr(struct request *rq, struct sg_io_v4 *hdr,
  		fmode_t mode)

  {

  	struct scsi_request *sreq = scsi_req(rq);

  	if (hdr->dout_xfer_len && hdr->din_xfer_len) {
  		pr_warn_once("BIDI support in bsg has been removed.
  ");
  		return -EOPNOTSUPP;
  	}

  	sreq->cmd_len = hdr->request_len;
  	if (sreq->cmd_len > BLK_MAX_CDB) {
  		sreq->cmd = kzalloc(sreq->cmd_len, GFP_KERNEL);
  		if (!sreq->cmd)

  			return -ENOMEM;
  	}

  	if (copy_from_user(sreq->cmd, uptr64(hdr->request), sreq->cmd_len))

  		return -EFAULT;

  	if (blk_verify_command(sreq->cmd, mode))

  		return -EPERM;

  	return 0;
  }

  static int bsg_scsi_complete_rq(struct request *rq, struct sg_io_v4 *hdr)

  {

  	struct scsi_request *sreq = scsi_req(rq);

  	int ret = 0;

  	/*
  	 * fill in all the output members
  	 */
  	hdr->device_status = sreq->result & 0xff;
  	hdr->transport_status = host_byte(sreq->result);
  	hdr->driver_status = driver_byte(sreq->result);
  	hdr->info = 0;
  	if (hdr->device_status || hdr->transport_status || hdr->driver_status)
  		hdr->info |= SG_INFO_CHECK;
  	hdr->response_len = 0;

  	if (sreq->sense_len && hdr->response) {
  		int len = min_t(unsigned int, hdr->max_response_len,
  					sreq->sense_len);
  
  		if (copy_to_user(uptr64(hdr->response), sreq->sense, len))
  			ret = -EFAULT;
  		else
  			hdr->response_len = len;
  	}

  	if (rq_data_dir(rq) == READ)

  		hdr->din_resid = sreq->resid_len;

  	else

  		hdr->dout_resid = sreq->resid_len;

  	return ret;

  }

  static void bsg_scsi_free_rq(struct request *rq)
  {
  	scsi_req_free_cmd(scsi_req(rq));
  }
  
  static const struct bsg_ops bsg_scsi_ops = {
  	.check_proto		= bsg_scsi_check_proto,
  	.fill_hdr		= bsg_scsi_fill_hdr,
  	.complete_rq		= bsg_scsi_complete_rq,
  	.free_rq		= bsg_scsi_free_rq,
  };

  static int bsg_sg_io(struct request_queue *q, fmode_t mode, void __user *uarg)

  {

  	struct request *rq;
  	struct bio *bio;

  	struct sg_io_v4 hdr;

  	int ret;

  	if (copy_from_user(&hdr, uarg, sizeof(hdr)))
  		return -EFAULT;

  	if (!q->bsg_dev.class_dev)
  		return -ENXIO;

  	if (hdr.guard != 'Q')
  		return -EINVAL;
  	ret = q->bsg_dev.ops->check_proto(&hdr);

  	if (ret)

  		return ret;

  	rq = blk_get_request(q, hdr.dout_xfer_len ?

  			REQ_OP_SCSI_OUT : REQ_OP_SCSI_IN, 0);

  	if (IS_ERR(rq))

  		return PTR_ERR(rq);

  	ret = q->bsg_dev.ops->fill_hdr(rq, &hdr, mode);

  	if (ret)

  		return ret;

  	rq->timeout = msecs_to_jiffies(hdr.timeout);

  	if (!rq->timeout)
  		rq->timeout = q->sg_timeout;
  	if (!rq->timeout)
  		rq->timeout = BLK_DEFAULT_SG_TIMEOUT;
  	if (rq->timeout < BLK_MIN_SG_TIMEOUT)
  		rq->timeout = BLK_MIN_SG_TIMEOUT;

  	if (hdr.dout_xfer_len) {
  		ret = blk_rq_map_user(q, rq, NULL, uptr64(hdr.dout_xferp),
  				hdr.dout_xfer_len, GFP_KERNEL);
  	} else if (hdr.din_xfer_len) {
  		ret = blk_rq_map_user(q, rq, NULL, uptr64(hdr.din_xferp),
  				hdr.din_xfer_len, GFP_KERNEL);

  	}

  	if (ret)

  		goto out_free_rq;

  	bio = rq->bio;

  	blk_execute_rq(q, NULL, rq, !(hdr.flags & BSG_FLAG_Q_AT_TAIL));
  	ret = rq->q->bsg_dev.ops->complete_rq(rq, &hdr);

  	blk_rq_unmap_user(bio);

  
  out_free_rq:

  	rq->q->bsg_dev.ops->free_rq(rq);

  	blk_put_request(rq);

  	if (!ret && copy_to_user(uarg, &hdr, sizeof(hdr)))

  		return -EFAULT;
  	return ret;

  }

  static struct bsg_device *bsg_alloc_device(void)
  {

  	struct bsg_device *bd;

  
  	bd = kzalloc(sizeof(struct bsg_device), GFP_KERNEL);
  	if (unlikely(!bd))
  		return NULL;
  
  	spin_lock_init(&bd->lock);

  	bd->max_queue = BSG_DEFAULT_CMDS;

  	INIT_HLIST_NODE(&bd->dev_list);

  	return bd;

  }
  
  static int bsg_put_device(struct bsg_device *bd)
  {

  	struct request_queue *q = bd->queue;

  
  	mutex_lock(&bsg_mutex);

  	if (!refcount_dec_and_test(&bd->ref_count)) {

  		mutex_unlock(&bsg_mutex);

  		return 0;

  	}
  
  	hlist_del(&bd->dev_list);
  	mutex_unlock(&bsg_mutex);

  	bsg_dbg(bd, "tearing down
  ");

  
  	/*
  	 * close can always block
  	 */

  	kfree(bd);

  	blk_put_queue(q);
  	return 0;

  }
  
  static struct bsg_device *bsg_add_device(struct inode *inode,

  					 struct request_queue *rq,

  					 struct file *file)
  {

  	struct bsg_device *bd;

  	unsigned char buf[32];

  	lockdep_assert_held(&bsg_mutex);

  	if (!blk_get_queue(rq))

  		return ERR_PTR(-ENXIO);

  
  	bd = bsg_alloc_device();

  	if (!bd) {
  		blk_put_queue(rq);

  		return ERR_PTR(-ENOMEM);

  	}

  	bd->queue = rq;

  	refcount_set(&bd->ref_count, 1);

  	hlist_add_head(&bd->dev_list, bsg_dev_idx_hash(iminor(inode)));

  	strncpy(bd->name, dev_name(rq->bsg_dev.class_dev), sizeof(bd->name) - 1);

  	bsg_dbg(bd, "bound to <%s>, max queue %d
  ",

  		format_dev_t(buf, inode->i_rdev), bd->max_queue);

  	return bd;
  }

  static struct bsg_device *__bsg_get_device(int minor, struct request_queue *q)

  {

  	struct bsg_device *bd;

  	lockdep_assert_held(&bsg_mutex);

  	hlist_for_each_entry(bd, bsg_dev_idx_hash(minor), dev_list) {

  		if (bd->queue == q) {

  			refcount_inc(&bd->ref_count);

  			goto found;

  		}

  	}

  	bd = NULL;
  found:

  	return bd;
  }
  
  static struct bsg_device *bsg_get_device(struct inode *inode, struct file *file)
  {

  	struct bsg_device *bd;
  	struct bsg_class_device *bcd;

  	/*
  	 * find the class device
  	 */

  	mutex_lock(&bsg_mutex);

  	bcd = idr_find(&bsg_minor_idr, iminor(inode));

  	if (!bcd) {
  		bd = ERR_PTR(-ENODEV);
  		goto out_unlock;
  	}

  	bd = __bsg_get_device(iminor(inode), bcd->queue);

  	if (!bd)
  		bd = bsg_add_device(inode, bcd->queue, file);

  out_unlock:
  	mutex_unlock(&bsg_mutex);

  	return bd;

  }
  
  static int bsg_open(struct inode *inode, struct file *file)
  {

  	struct bsg_device *bd;

  	bd = bsg_get_device(inode, file);

  
  	if (IS_ERR(bd))
  		return PTR_ERR(bd);
  
  	file->private_data = bd;
  	return 0;
  }
  
  static int bsg_release(struct inode *inode, struct file *file)
  {
  	struct bsg_device *bd = file->private_data;
  
  	file->private_data = NULL;
  	return bsg_put_device(bd);
  }

  static int bsg_get_command_q(struct bsg_device *bd, int __user *uarg)
  {
  	return put_user(bd->max_queue, uarg);
  }
  
  static int bsg_set_command_q(struct bsg_device *bd, int __user *uarg)
  {
  	int queue;
  
  	if (get_user(queue, uarg))
  		return -EFAULT;
  	if (queue < 1)
  		return -EINVAL;
  
  	spin_lock_irq(&bd->lock);
  	bd->max_queue = queue;
  	spin_unlock_irq(&bd->lock);
  	return 0;
  }

  static long bsg_ioctl(struct file *file, unsigned int cmd, unsigned long arg)

  {
  	struct bsg_device *bd = file->private_data;

  	void __user *uarg = (void __user *) arg;

  	switch (cmd) {

  	/*
  	 * Our own ioctls
  	 */

  	case SG_GET_COMMAND_Q:

  		return bsg_get_command_q(bd, uarg);
  	case SG_SET_COMMAND_Q:
  		return bsg_set_command_q(bd, uarg);

  
  	/*
  	 * SCSI/sg ioctls
  	 */
  	case SG_GET_VERSION_NUM:
  	case SCSI_IOCTL_GET_IDLUN:
  	case SCSI_IOCTL_GET_BUS_NUMBER:
  	case SG_SET_TIMEOUT:
  	case SG_GET_TIMEOUT:
  	case SG_GET_RESERVED_SIZE:
  	case SG_SET_RESERVED_SIZE:
  	case SG_EMULATED_HOST:

  	case SCSI_IOCTL_SEND_COMMAND:

  		return scsi_cmd_ioctl(bd->queue, NULL, file->f_mode, cmd, uarg);

  	case SG_IO:
  		return bsg_sg_io(bd->queue, file->f_mode, uarg);

  	default:

  		return -ENOTTY;

  	}
  }

  static const struct file_operations bsg_fops = {

  	.open		=	bsg_open,
  	.release	=	bsg_release,

  	.unlocked_ioctl	=	bsg_ioctl,

  	.owner		=	THIS_MODULE,

  	.llseek		=	default_llseek,

  };

  void bsg_unregister_queue(struct request_queue *q)

  {

  	struct bsg_class_device *bcd = &q->bsg_dev;

  	if (!bcd->class_dev)
  		return;

  
  	mutex_lock(&bsg_mutex);

  	idr_remove(&bsg_minor_idr, bcd->minor);

  	if (q->kobj.sd)
  		sysfs_remove_link(&q->kobj, "bsg");

  	device_unregister(bcd->class_dev);

  	bcd->class_dev = NULL;

  	mutex_unlock(&bsg_mutex);
  }

  EXPORT_SYMBOL_GPL(bsg_unregister_queue);

  int bsg_register_queue(struct request_queue *q, struct device *parent,

  		const char *name, const struct bsg_ops *ops)

  {

  	struct bsg_class_device *bcd;

  	dev_t dev;

  	int ret;

  	struct device *class_dev = NULL;

  
  	/*
  	 * we need a proper transport to send commands, not a stacked device
  	 */

  	if (!queue_is_mq(q))

  		return 0;

  	bcd = &q->bsg_dev;

  	memset(bcd, 0, sizeof(*bcd));

  
  	mutex_lock(&bsg_mutex);

  	ret = idr_alloc(&bsg_minor_idr, bcd, 0, BSG_MAX_DEVS, GFP_KERNEL);
  	if (ret < 0) {
  		if (ret == -ENOSPC) {
  			printk(KERN_ERR "bsg: too many bsg devices
  ");
  			ret = -EINVAL;
  		}

  		goto unlock;

  	}

  	bcd->minor = ret;

  	bcd->queue = q;

  	bcd->ops = ops;

  	dev = MKDEV(bsg_major, bcd->minor);

  	class_dev = device_create(bsg_class, parent, dev, NULL, "%s", name);

  	if (IS_ERR(class_dev)) {
  		ret = PTR_ERR(class_dev);

  		goto idr_remove;

  	}
  	bcd->class_dev = class_dev;

  	if (q->kobj.sd) {

  		ret = sysfs_create_link(&q->kobj, &bcd->class_dev->kobj, "bsg");
  		if (ret)

  			goto unregister_class_dev;

  	}

  	mutex_unlock(&bsg_mutex);
  	return 0;

  unregister_class_dev:

  	device_unregister(class_dev);

  idr_remove:

  	idr_remove(&bsg_minor_idr, bcd->minor);

  unlock:

  	mutex_unlock(&bsg_mutex);

  	return ret;
  }

  
  int bsg_scsi_register_queue(struct request_queue *q, struct device *parent)
  {
  	if (!blk_queue_scsi_passthrough(q)) {
  		WARN_ONCE(true, "Attempt to register a non-SCSI queue
  ");
  		return -EINVAL;
  	}

  	return bsg_register_queue(q, parent, dev_name(parent), &bsg_scsi_ops);

  }
  EXPORT_SYMBOL_GPL(bsg_scsi_register_queue);

  static struct cdev bsg_cdev;

  static char *bsg_devnode(struct device *dev, umode_t *mode)

  {
  	return kasprintf(GFP_KERNEL, "bsg/%s", dev_name(dev));
  }

  static int __init bsg_init(void)
  {
  	int ret, i;

  	dev_t devid;

  	for (i = 0; i < BSG_LIST_ARRAY_SIZE; i++)

  		INIT_HLIST_HEAD(&bsg_device_list[i]);
  
  	bsg_class = class_create(THIS_MODULE, "bsg");

  	if (IS_ERR(bsg_class))
  		return PTR_ERR(bsg_class);

  	bsg_class->devnode = bsg_devnode;

  	ret = alloc_chrdev_region(&devid, 0, BSG_MAX_DEVS, "bsg");

  	if (ret)
  		goto destroy_bsg_class;

  	bsg_major = MAJOR(devid);

  	cdev_init(&bsg_cdev, &bsg_fops);

  	ret = cdev_add(&bsg_cdev, MKDEV(bsg_major, 0), BSG_MAX_DEVS);

  	if (ret)
  		goto unregister_chrdev;

  	printk(KERN_INFO BSG_DESCRIPTION " version " BSG_VERSION

  	       " loaded (major %d)
  ", bsg_major);

  	return 0;

  unregister_chrdev:
  	unregister_chrdev_region(MKDEV(bsg_major, 0), BSG_MAX_DEVS);
  destroy_bsg_class:
  	class_destroy(bsg_class);

  	return ret;

  }
  
  MODULE_AUTHOR("Jens Axboe");

  MODULE_DESCRIPTION(BSG_DESCRIPTION);

  MODULE_LICENSE("GPL");

  device_initcall(bsg_init);