/*
   * Linux host-side vring helpers; for when the kernel needs to access
   * someone else's vring.
   *
   * Copyright IBM Corporation, 2013.
   * Parts taken from drivers/vhost/vhost.c Copyright 2009 Red Hat, Inc.
   *
   * 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.
   *
   * Written by: Rusty Russell <rusty@rustcorp.com.au>
   */
  #ifndef _LINUX_VRINGH_H
  #define _LINUX_VRINGH_H
  #include <uapi/linux/virtio_ring.h>
  #include <linux/uio.h>
  #include <linux/slab.h>
  #include <asm/barrier.h>
  
  /* virtio_ring with information needed for host access. */
  struct vringh {
  	/* Guest publishes used event idx (note: we always do). */
  	bool event_indices;
  
  	/* Can we get away with weak barriers? */
  	bool weak_barriers;
  
  	/* Last available index we saw (ie. where we're up to). */
  	u16 last_avail_idx;
  
  	/* Last index we used. */
  	u16 last_used_idx;
  
  	/* How many descriptors we've completed since last need_notify(). */
  	u32 completed;
  
  	/* The vring (note: it may contain user pointers!) */
  	struct vring vring;
  
  	/* The function to call to notify the guest about added buffers */
  	void (*notify)(struct vringh *);
  };
  
  /**
   * struct vringh_config_ops - ops for creating a host vring from a virtio driver
   * @find_vrhs: find the host vrings and instantiate them
   *	vdev: the virtio_device
   *	nhvrs: the number of host vrings to find
   *	hvrs: on success, includes new host vrings
   *	callbacks: array of driver callbacks, for each host vring
   *		include a NULL entry for vqs that do not need a callback
   *	Returns 0 on success or error status
   * @del_vrhs: free the host vrings found by find_vrhs().
   */
  struct virtio_device;
  typedef void vrh_callback_t(struct virtio_device *, struct vringh *);
  struct vringh_config_ops {
  	int (*find_vrhs)(struct virtio_device *vdev, unsigned nhvrs,
  			 struct vringh *vrhs[], vrh_callback_t *callbacks[]);
  	void (*del_vrhs)(struct virtio_device *vdev);
  };
  
  /* The memory the vring can access, and what offset to apply. */
  struct vringh_range {
  	u64 start, end_incl;
  	u64 offset;
  };
  
  /**
   * struct vringh_iov - iovec mangler.
   *
   * Mangles iovec in place, and restores it.
   * Remaining data is iov + i, of used - i elements.
   */
  struct vringh_iov {
  	struct iovec *iov;
  	size_t consumed; /* Within iov[i] */
  	unsigned i, used, max_num;
  };
  
  /**
   * struct vringh_iov - kvec mangler.
   *
   * Mangles kvec in place, and restores it.
   * Remaining data is iov + i, of used - i elements.
   */
  struct vringh_kiov {
  	struct kvec *iov;
  	size_t consumed; /* Within iov[i] */
  	unsigned i, used, max_num;
  };
  
  /* Flag on max_num to indicate we're kmalloced. */
  #define VRINGH_IOV_ALLOCATED 0x8000000
  
  /* Helpers for userspace vrings. */
  int vringh_init_user(struct vringh *vrh, u32 features,
  		     unsigned int num, bool weak_barriers,
  		     struct vring_desc __user *desc,
  		     struct vring_avail __user *avail,
  		     struct vring_used __user *used);
  
  static inline void vringh_iov_init(struct vringh_iov *iov,
  				   struct iovec *iovec, unsigned num)
  {
  	iov->used = iov->i = 0;
  	iov->consumed = 0;
  	iov->max_num = num;
  	iov->iov = iovec;
  }
  
  static inline void vringh_iov_reset(struct vringh_iov *iov)
  {
  	iov->iov[iov->i].iov_len += iov->consumed;
  	iov->iov[iov->i].iov_base -= iov->consumed;
  	iov->consumed = 0;
  	iov->i = 0;
  }
  
  static inline void vringh_iov_cleanup(struct vringh_iov *iov)
  {
  	if (iov->max_num & VRINGH_IOV_ALLOCATED)
  		kfree(iov->iov);
  	iov->max_num = iov->used = iov->i = iov->consumed = 0;
  	iov->iov = NULL;
  }
  
  /* Convert a descriptor into iovecs. */
  int vringh_getdesc_user(struct vringh *vrh,
  			struct vringh_iov *riov,
  			struct vringh_iov *wiov,
  			bool (*getrange)(struct vringh *vrh,
  					 u64 addr, struct vringh_range *r),
  			u16 *head);
  
  /* Copy bytes from readable vsg, consuming it (and incrementing wiov->i). */
  ssize_t vringh_iov_pull_user(struct vringh_iov *riov, void *dst, size_t len);
  
  /* Copy bytes into writable vsg, consuming it (and incrementing wiov->i). */
  ssize_t vringh_iov_push_user(struct vringh_iov *wiov,
  			     const void *src, size_t len);
  
  /* Mark a descriptor as used. */
  int vringh_complete_user(struct vringh *vrh, u16 head, u32 len);
  int vringh_complete_multi_user(struct vringh *vrh,
  			       const struct vring_used_elem used[],
  			       unsigned num_used);
  
  /* Pretend we've never seen descriptor (for easy error handling). */
  void vringh_abandon_user(struct vringh *vrh, unsigned int num);
  
  /* Do we need to fire the eventfd to notify the other side? */
  int vringh_need_notify_user(struct vringh *vrh);
  
  bool vringh_notify_enable_user(struct vringh *vrh);
  void vringh_notify_disable_user(struct vringh *vrh);
  
  /* Helpers for kernelspace vrings. */
  int vringh_init_kern(struct vringh *vrh, u32 features,
  		     unsigned int num, bool weak_barriers,
  		     struct vring_desc *desc,
  		     struct vring_avail *avail,
  		     struct vring_used *used);
  
  static inline void vringh_kiov_init(struct vringh_kiov *kiov,
  				    struct kvec *kvec, unsigned num)
  {
  	kiov->used = kiov->i = 0;
  	kiov->consumed = 0;
  	kiov->max_num = num;
  	kiov->iov = kvec;
  }
  
  static inline void vringh_kiov_reset(struct vringh_kiov *kiov)
  {
  	kiov->iov[kiov->i].iov_len += kiov->consumed;
  	kiov->iov[kiov->i].iov_base -= kiov->consumed;
  	kiov->consumed = 0;
  	kiov->i = 0;
  }
  
  static inline void vringh_kiov_cleanup(struct vringh_kiov *kiov)
  {
  	if (kiov->max_num & VRINGH_IOV_ALLOCATED)
  		kfree(kiov->iov);
  	kiov->max_num = kiov->used = kiov->i = kiov->consumed = 0;
  	kiov->iov = NULL;
  }
  
  int vringh_getdesc_kern(struct vringh *vrh,
  			struct vringh_kiov *riov,
  			struct vringh_kiov *wiov,
  			u16 *head,
  			gfp_t gfp);
  
  ssize_t vringh_iov_pull_kern(struct vringh_kiov *riov, void *dst, size_t len);
  ssize_t vringh_iov_push_kern(struct vringh_kiov *wiov,
  			     const void *src, size_t len);
  void vringh_abandon_kern(struct vringh *vrh, unsigned int num);
  int vringh_complete_kern(struct vringh *vrh, u16 head, u32 len);
  
  bool vringh_notify_enable_kern(struct vringh *vrh);
  void vringh_notify_disable_kern(struct vringh *vrh);
  
  int vringh_need_notify_kern(struct vringh *vrh);
  
  /* Notify the guest about buffers added to the used ring */
  static inline void vringh_notify(struct vringh *vrh)
  {
  	if (vrh->notify)
  		vrh->notify(vrh);
  }
  
  #endif /* _LINUX_VRINGH_H */