/*
   * SCSI target kernel/user interface functions
   *
   * Copyright (C) 2005 FUJITA Tomonori <tomof@acm.org>
   * Copyright (C) 2005 Mike Christie <michaelc@cs.wisc.edu>
   *
   * 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., 51 Franklin St, Fifth Floor, Boston, MA
   * 02110-1301 USA
   */
  #include <linux/miscdevice.h>

  #include <linux/gfp.h>

  #include <linux/file.h>

  #include <linux/export.h>

  #include <net/tcp.h>
  #include <scsi/scsi.h>
  #include <scsi/scsi_cmnd.h>
  #include <scsi/scsi_device.h>
  #include <scsi/scsi_host.h>
  #include <scsi/scsi_tgt.h>
  #include <scsi/scsi_tgt_if.h>

  #include <asm/cacheflush.h>

  #include "scsi_tgt_priv.h"

  #if TGT_RING_SIZE < PAGE_SIZE
  #  define TGT_RING_SIZE PAGE_SIZE
  #endif
  
  #define TGT_RING_PAGES (TGT_RING_SIZE >> PAGE_SHIFT)
  #define TGT_EVENT_PER_PAGE (PAGE_SIZE / sizeof(struct tgt_event))
  #define TGT_MAX_EVENTS (TGT_EVENT_PER_PAGE * TGT_RING_PAGES)

  struct tgt_ring {
  	u32 tr_idx;
  	unsigned long tr_pages[TGT_RING_PAGES];
  	spinlock_t tr_lock;
  };
  
  /* tx_ring : kernel->user, rx_ring : user->kernel */
  static struct tgt_ring tx_ring, rx_ring;
  static DECLARE_WAIT_QUEUE_HEAD(tgt_poll_wait);
  
  static inline void tgt_ring_idx_inc(struct tgt_ring *ring)
  {
  	if (ring->tr_idx == TGT_MAX_EVENTS - 1)
  		ring->tr_idx = 0;
  	else
  		ring->tr_idx++;
  }
  
  static struct tgt_event *tgt_head_event(struct tgt_ring *ring, u32 idx)
  {
  	u32 pidx, off;
  
  	pidx = idx / TGT_EVENT_PER_PAGE;
  	off = idx % TGT_EVENT_PER_PAGE;
  
  	return (struct tgt_event *)
  		(ring->tr_pages[pidx] + sizeof(struct tgt_event) * off);
  }
  
  static int tgt_uspace_send_event(u32 type, struct tgt_event *p)
  {
  	struct tgt_event *ev;
  	struct tgt_ring *ring = &tx_ring;
  	unsigned long flags;
  	int err = 0;
  
  	spin_lock_irqsave(&ring->tr_lock, flags);
  
  	ev = tgt_head_event(ring, ring->tr_idx);
  	if (!ev->hdr.status)
  		tgt_ring_idx_inc(ring);
  	else
  		err = -BUSY;
  
  	spin_unlock_irqrestore(&ring->tr_lock, flags);
  
  	if (err)
  		return err;
  
  	memcpy(ev, p, sizeof(*ev));
  	ev->hdr.type = type;
  	mb();
  	ev->hdr.status = 1;
  
  	flush_dcache_page(virt_to_page(ev));
  
  	wake_up_interruptible(&tgt_poll_wait);
  
  	return 0;
  }

  int scsi_tgt_uspace_send_cmd(struct scsi_cmnd *cmd, u64 itn_id,
  			     struct scsi_lun *lun, u64 tag)

  {
  	struct Scsi_Host *shost = scsi_tgt_cmd_to_host(cmd);
  	struct tgt_event ev;
  	int err;
  
  	memset(&ev, 0, sizeof(ev));
  	ev.p.cmd_req.host_no = shost->host_no;

  	ev.p.cmd_req.itn_id = itn_id;

  	ev.p.cmd_req.data_len = scsi_bufflen(cmd);

  	memcpy(ev.p.cmd_req.scb, cmd->cmnd, sizeof(ev.p.cmd_req.scb));
  	memcpy(ev.p.cmd_req.lun, lun, sizeof(ev.p.cmd_req.lun));
  	ev.p.cmd_req.attribute = cmd->tag;
  	ev.p.cmd_req.tag = tag;
  
  	dprintk("%p %d %u %x %llx
  ", cmd, shost->host_no,
  		ev.p.cmd_req.data_len, cmd->tag,
  		(unsigned long long) ev.p.cmd_req.tag);
  
  	err = tgt_uspace_send_event(TGT_KEVENT_CMD_REQ, &ev);
  	if (err)
  		eprintk("tx buf is full, could not send
  ");
  
  	return err;
  }

  int scsi_tgt_uspace_send_status(struct scsi_cmnd *cmd, u64 itn_id, u64 tag)

  {
  	struct Scsi_Host *shost = scsi_tgt_cmd_to_host(cmd);
  	struct tgt_event ev;
  	int err;
  
  	memset(&ev, 0, sizeof(ev));
  	ev.p.cmd_done.host_no = shost->host_no;

  	ev.p.cmd_done.itn_id = itn_id;

  	ev.p.cmd_done.tag = tag;
  	ev.p.cmd_done.result = cmd->result;
  
  	dprintk("%p %d %llu %u %x
  ", cmd, shost->host_no,
  		(unsigned long long) ev.p.cmd_req.tag,
  		ev.p.cmd_req.data_len, cmd->tag);
  
  	err = tgt_uspace_send_event(TGT_KEVENT_CMD_DONE, &ev);
  	if (err)
  		eprintk("tx buf is full, could not send
  ");
  
  	return err;
  }

  int scsi_tgt_uspace_send_tsk_mgmt(int host_no, u64 itn_id, int function,
  				  u64 tag, struct scsi_lun *scsilun, void *data)

  {
  	struct tgt_event ev;
  	int err;
  
  	memset(&ev, 0, sizeof(ev));
  	ev.p.tsk_mgmt_req.host_no = host_no;

  	ev.p.tsk_mgmt_req.itn_id = itn_id;

  	ev.p.tsk_mgmt_req.function = function;
  	ev.p.tsk_mgmt_req.tag = tag;
  	memcpy(ev.p.tsk_mgmt_req.lun, scsilun, sizeof(ev.p.tsk_mgmt_req.lun));
  	ev.p.tsk_mgmt_req.mid = (u64) (unsigned long) data;
  
  	dprintk("%d %x %llx %llx
  ", host_no, function, (unsigned long long) tag,
  		(unsigned long long) ev.p.tsk_mgmt_req.mid);
  
  	err = tgt_uspace_send_event(TGT_KEVENT_TSK_MGMT_REQ, &ev);
  	if (err)
  		eprintk("tx buf is full, could not send
  ");
  
  	return err;
  }

  int scsi_tgt_uspace_send_it_nexus_request(int host_no, u64 itn_id,
  					  int function, char *initiator_id)
  {
  	struct tgt_event ev;
  	int err;
  
  	memset(&ev, 0, sizeof(ev));
  	ev.p.it_nexus_req.host_no = host_no;
  	ev.p.it_nexus_req.function = function;
  	ev.p.it_nexus_req.itn_id = itn_id;
  	if (initiator_id)
  		strncpy(ev.p.it_nexus_req.initiator_id, initiator_id,
  			sizeof(ev.p.it_nexus_req.initiator_id));
  
  	dprintk("%d %x %llx
  ", host_no, function, (unsigned long long)itn_id);
  
  	err = tgt_uspace_send_event(TGT_KEVENT_IT_NEXUS_REQ, &ev);
  	if (err)
  		eprintk("tx buf is full, could not send
  ");
  
  	return err;
  }

  static int event_recv_msg(struct tgt_event *ev)
  {
  	int err = 0;
  
  	switch (ev->hdr.type) {
  	case TGT_UEVENT_CMD_RSP:
  		err = scsi_tgt_kspace_exec(ev->p.cmd_rsp.host_no,

  					   ev->p.cmd_rsp.itn_id,

  					   ev->p.cmd_rsp.result,

  					   ev->p.cmd_rsp.tag,

  					   ev->p.cmd_rsp.uaddr,

  					   ev->p.cmd_rsp.len,
  					   ev->p.cmd_rsp.sense_uaddr,
  					   ev->p.cmd_rsp.sense_len,

  					   ev->p.cmd_rsp.rw);
  		break;
  	case TGT_UEVENT_TSK_MGMT_RSP:
  		err = scsi_tgt_kspace_tsk_mgmt(ev->p.tsk_mgmt_rsp.host_no,

  					       ev->p.tsk_mgmt_rsp.itn_id,

  					       ev->p.tsk_mgmt_rsp.mid,
  					       ev->p.tsk_mgmt_rsp.result);
  		break;

  	case TGT_UEVENT_IT_NEXUS_RSP:
  		err = scsi_tgt_kspace_it_nexus_rsp(ev->p.it_nexus_rsp.host_no,
  						   ev->p.it_nexus_rsp.itn_id,
  						   ev->p.it_nexus_rsp.result);
  		break;

  	default:
  		eprintk("unknown type %d
  ", ev->hdr.type);
  		err = -EINVAL;
  	}
  
  	return err;
  }
  
  static ssize_t tgt_write(struct file *file, const char __user * buffer,
  			 size_t count, loff_t * ppos)
  {
  	struct tgt_event *ev;
  	struct tgt_ring *ring = &rx_ring;
  
  	while (1) {
  		ev = tgt_head_event(ring, ring->tr_idx);
  		/* do we need this? */
  		flush_dcache_page(virt_to_page(ev));
  
  		if (!ev->hdr.status)
  			break;
  
  		tgt_ring_idx_inc(ring);
  		event_recv_msg(ev);
  		ev->hdr.status = 0;
  	};
  
  	return count;
  }
  
  static unsigned int tgt_poll(struct file * file, struct poll_table_struct *wait)
  {
  	struct tgt_event *ev;
  	struct tgt_ring *ring = &tx_ring;
  	unsigned long flags;
  	unsigned int mask = 0;
  	u32 idx;
  
  	poll_wait(file, &tgt_poll_wait, wait);
  
  	spin_lock_irqsave(&ring->tr_lock, flags);
  
  	idx = ring->tr_idx ? ring->tr_idx - 1 : TGT_MAX_EVENTS - 1;
  	ev = tgt_head_event(ring, idx);
  	if (ev->hdr.status)
  		mask |= POLLIN | POLLRDNORM;
  
  	spin_unlock_irqrestore(&ring->tr_lock, flags);
  
  	return mask;
  }
  
  static int uspace_ring_map(struct vm_area_struct *vma, unsigned long addr,
  			   struct tgt_ring *ring)
  {
  	int i, err;
  
  	for (i = 0; i < TGT_RING_PAGES; i++) {
  		struct page *page = virt_to_page(ring->tr_pages[i]);
  		err = vm_insert_page(vma, addr, page);
  		if (err)
  			return err;
  		addr += PAGE_SIZE;
  	}
  
  	return 0;
  }
  
  static int tgt_mmap(struct file *filp, struct vm_area_struct *vma)
  {
  	unsigned long addr;
  	int err;
  
  	if (vma->vm_pgoff)
  		return -EINVAL;
  
  	if (vma->vm_end - vma->vm_start != TGT_RING_SIZE * 2) {
  		eprintk("mmap size must be %lu, not %lu 
  ",
  			TGT_RING_SIZE * 2, vma->vm_end - vma->vm_start);
  		return -EINVAL;
  	}
  
  	addr = vma->vm_start;
  	err = uspace_ring_map(vma, addr, &tx_ring);
  	if (err)
  		return err;
  	err = uspace_ring_map(vma, addr + TGT_RING_SIZE, &rx_ring);
  
  	return err;
  }
  
  static int tgt_open(struct inode *inode, struct file *file)
  {
  	tx_ring.tr_idx = rx_ring.tr_idx = 0;
  
  	return 0;
  }

  static const struct file_operations tgt_fops = {

  	.owner		= THIS_MODULE,
  	.open		= tgt_open,
  	.poll		= tgt_poll,
  	.write		= tgt_write,
  	.mmap		= tgt_mmap,

  	.llseek		= noop_llseek,

  };
  
  static struct miscdevice tgt_miscdev = {
  	.minor = MISC_DYNAMIC_MINOR,
  	.name = "tgt",
  	.fops = &tgt_fops,
  };
  
  static void tgt_ring_exit(struct tgt_ring *ring)
  {
  	int i;
  
  	for (i = 0; i < TGT_RING_PAGES; i++)
  		free_page(ring->tr_pages[i]);
  }
  
  static int tgt_ring_init(struct tgt_ring *ring)
  {
  	int i;
  
  	spin_lock_init(&ring->tr_lock);
  
  	for (i = 0; i < TGT_RING_PAGES; i++) {
  		ring->tr_pages[i] = get_zeroed_page(GFP_KERNEL);
  		if (!ring->tr_pages[i]) {
  			eprintk("out of memory
  ");
  			return -ENOMEM;
  		}
  	}
  
  	return 0;
  }
  
  void scsi_tgt_if_exit(void)
  {
  	tgt_ring_exit(&tx_ring);
  	tgt_ring_exit(&rx_ring);
  	misc_deregister(&tgt_miscdev);
  }
  
  int scsi_tgt_if_init(void)
  {
  	int err;
  
  	err = tgt_ring_init(&tx_ring);
  	if (err)
  		return err;
  
  	err = tgt_ring_init(&rx_ring);
  	if (err)
  		goto free_tx_ring;
  
  	err = misc_register(&tgt_miscdev);
  	if (err)
  		goto free_rx_ring;
  
  	return 0;
  free_rx_ring:
  	tgt_ring_exit(&rx_ring);
  free_tx_ring:
  	tgt_ring_exit(&tx_ring);
  
  	return err;
  }