text: // SPDX-License-Identifier: GPL-2.0
  #include <linux/bsg.h>
  #include <scsi/scsi.h>
  #include <scsi/scsi_ioctl.h>
  #include <scsi/scsi_cmnd.h>
  #include <scsi/scsi_device.h>
  #include <scsi/sg.h>
  #include "scsi_priv.h"
  
  #define uptr64(val) ((void __user *)(uintptr_t)(val))
  
  static int scsi_bsg_sg_io_fn(struct request_queue *q, struct sg_io_v4 *hdr,
  		fmode_t mode, unsigned int timeout)
  {
  	struct scsi_request *sreq;
  	struct request *rq;
  	struct bio *bio;
  	int ret;
  
  	if (hdr->protocol != BSG_PROTOCOL_SCSI  ||
  	    hdr->subprotocol != BSG_SUB_PROTOCOL_SCSI_CMD)
  		return -EINVAL;
  	if (hdr->dout_xfer_len && hdr->din_xfer_len) {
  		pr_warn_once("BIDI support in bsg has been removed.\n");
  		return -EOPNOTSUPP;
  	}
  
  	rq = scsi_alloc_request(q, hdr->dout_xfer_len ?
  				REQ_OP_DRV_OUT : REQ_OP_DRV_IN, 0);
  	if (IS_ERR(rq))
  		return PTR_ERR(rq);
  	rq->timeout = timeout;
  
  	ret = -ENOMEM;
  	sreq = scsi_req(rq);
  	sreq->cmd_len = hdr->request_len;
  	if (sreq->cmd_len > BLK_MAX_CDB) {
  		sreq->cmd = kzalloc(sreq->cmd_len, GFP_KERNEL);
  		if (!sreq->cmd)
  			goto out_put_request;
  	}
  
  	ret = -EFAULT;
  	if (copy_from_user(sreq->cmd, uptr64(hdr->request), sreq->cmd_len))
  		goto out_free_cmd;
  	ret = -EPERM;
  	if (!scsi_cmd_allowed(sreq->cmd, mode))
  		goto out_free_cmd;
  
  	ret = 0;
  	if (hdr->dout_xfer_len) {
  		ret = blk_rq_map_user(rq->q, rq, NULL, uptr64(hdr->dout_xferp),
  				hdr->dout_xfer_len, GFP_KERNEL);
  	} else if (hdr->din_xfer_len) {
  		ret = blk_rq_map_user(rq->q, rq, NULL, uptr64(hdr->din_xferp),
  				hdr->din_xfer_len, GFP_KERNEL);
  	}
  
  	if (ret)
  		goto out_free_cmd;
  
  	bio = rq->bio;
  	blk_execute_rq(rq, !(hdr->flags & BSG_FLAG_Q_AT_TAIL));
  
  	/*
  	 * fill in all the output members
  	 */
  	hdr->device_status = sreq->result & 0xff;
  	hdr->transport_status = host_byte(sreq->result);
  	hdr->driver_status = 0;
  	if (scsi_status_is_check_condition(sreq->result))
  		hdr->driver_status = DRIVER_SENSE;
  	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;
  
  	blk_rq_unmap_user(bio);
  
  out_free_cmd:
  	scsi_req_free_cmd(scsi_req(rq));
  out_put_request:
  	blk_mq_free_request(rq);
  	return ret;
  }
  
  struct bsg_device *scsi_bsg_register_queue(struct scsi_device *sdev)
  {
  	return bsg_register_queue(sdev->request_queue, &sdev->sdev_gendev,
  			dev_name(&sdev->sdev_gendev), scsi_bsg_sg_io_fn);
  }
  