/*
   * PCI Backend - Provides a Virtual PCI bus (with real devices)
   *               to the frontend
   *
   *   Author: Ryan Wilson <hap9@epoch.ncsc.mil>
   */
  
  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  
  #include <linux/list.h>
  #include <linux/slab.h>
  #include <linux/pci.h>
  #include <linux/mutex.h>
  #include "pciback.h"
  
  #define PCI_SLOT_MAX 32
  
  struct vpci_dev_data {
  	/* Access to dev_list must be protected by lock */
  	struct list_head dev_list[PCI_SLOT_MAX];
  	struct mutex lock;
  };
  
  static inline struct list_head *list_first(struct list_head *head)
  {
  	return head->next;
  }
  
  static struct pci_dev *__xen_pcibk_get_pci_dev(struct xen_pcibk_device *pdev,
  					       unsigned int domain,
  					       unsigned int bus,
  					       unsigned int devfn)
  {
  	struct pci_dev_entry *entry;
  	struct pci_dev *dev = NULL;
  	struct vpci_dev_data *vpci_dev = pdev->pci_dev_data;
  
  	if (domain != 0 || bus != 0)
  		return NULL;
  
  	if (PCI_SLOT(devfn) < PCI_SLOT_MAX) {
  		mutex_lock(&vpci_dev->lock);
  
  		list_for_each_entry(entry,
  				    &vpci_dev->dev_list[PCI_SLOT(devfn)],
  				    list) {
  			if (PCI_FUNC(entry->dev->devfn) == PCI_FUNC(devfn)) {
  				dev = entry->dev;
  				break;
  			}
  		}
  
  		mutex_unlock(&vpci_dev->lock);
  	}
  	return dev;
  }
  
  static inline int match_slot(struct pci_dev *l, struct pci_dev *r)
  {
  	if (pci_domain_nr(l->bus) == pci_domain_nr(r->bus)
  	    && l->bus == r->bus && PCI_SLOT(l->devfn) == PCI_SLOT(r->devfn))
  		return 1;
  
  	return 0;
  }
  
  static int __xen_pcibk_add_pci_dev(struct xen_pcibk_device *pdev,
  				   struct pci_dev *dev, int devid,
  				   publish_pci_dev_cb publish_cb)
  {
  	int err = 0, slot, func = -1;
  	struct pci_dev_entry *t, *dev_entry;
  	struct vpci_dev_data *vpci_dev = pdev->pci_dev_data;
  
  	if ((dev->class >> 24) == PCI_BASE_CLASS_BRIDGE) {
  		err = -EFAULT;
  		xenbus_dev_fatal(pdev->xdev, err,
  				 "Can't export bridges on the virtual PCI bus");
  		goto out;
  	}
  
  	dev_entry = kmalloc(sizeof(*dev_entry), GFP_KERNEL);
  	if (!dev_entry) {
  		err = -ENOMEM;
  		xenbus_dev_fatal(pdev->xdev, err,
  				 "Error adding entry to virtual PCI bus");
  		goto out;
  	}
  
  	dev_entry->dev = dev;
  
  	mutex_lock(&vpci_dev->lock);
  
  	/*
  	 * Keep multi-function devices together on the virtual PCI bus, except
  	 * virtual functions.
  	 */
  	if (!dev->is_virtfn) {
  		for (slot = 0; slot < PCI_SLOT_MAX; slot++) {
  			if (list_empty(&vpci_dev->dev_list[slot]))
  				continue;
  
  			t = list_entry(list_first(&vpci_dev->dev_list[slot]),
  				       struct pci_dev_entry, list);
  
  			if (match_slot(dev, t->dev)) {
  				pr_info("vpci: %s: assign to virtual slot %d func %d
  ",
  					pci_name(dev), slot,
  					PCI_FUNC(dev->devfn));
  				list_add_tail(&dev_entry->list,
  					      &vpci_dev->dev_list[slot]);
  				func = PCI_FUNC(dev->devfn);
  				goto unlock;
  			}
  		}
  	}
  
  	/* Assign to a new slot on the virtual PCI bus */
  	for (slot = 0; slot < PCI_SLOT_MAX; slot++) {
  		if (list_empty(&vpci_dev->dev_list[slot])) {
  			pr_info("vpci: %s: assign to virtual slot %d
  ",
  				pci_name(dev), slot);
  			list_add_tail(&dev_entry->list,
  				      &vpci_dev->dev_list[slot]);
  			func = dev->is_virtfn ? 0 : PCI_FUNC(dev->devfn);
  			goto unlock;
  		}
  	}
  
  	err = -ENOMEM;
  	xenbus_dev_fatal(pdev->xdev, err,
  			 "No more space on root virtual PCI bus");
  
  unlock:
  	mutex_unlock(&vpci_dev->lock);
  
  	/* Publish this device. */
  	if (!err)
  		err = publish_cb(pdev, 0, 0, PCI_DEVFN(slot, func), devid);
  	else
  		kfree(dev_entry);
  
  out:
  	return err;
  }
  
  static void __xen_pcibk_release_pci_dev(struct xen_pcibk_device *pdev,
  					struct pci_dev *dev, bool lock)
  {
  	int slot;
  	struct vpci_dev_data *vpci_dev = pdev->pci_dev_data;
  	struct pci_dev *found_dev = NULL;
  
  	mutex_lock(&vpci_dev->lock);
  
  	for (slot = 0; slot < PCI_SLOT_MAX; slot++) {
  		struct pci_dev_entry *e;
  
  		list_for_each_entry(e, &vpci_dev->dev_list[slot], list) {
  			if (e->dev == dev) {
  				list_del(&e->list);
  				found_dev = e->dev;
  				kfree(e);
  				goto out;
  			}
  		}
  	}
  
  out:
  	mutex_unlock(&vpci_dev->lock);
  
  	if (found_dev) {
  		if (lock)
  			device_lock(&found_dev->dev);
  		pcistub_put_pci_dev(found_dev);
  		if (lock)
  			device_unlock(&found_dev->dev);
  	}
  }
  
  static int __xen_pcibk_init_devices(struct xen_pcibk_device *pdev)
  {
  	int slot;
  	struct vpci_dev_data *vpci_dev;
  
  	vpci_dev = kmalloc(sizeof(*vpci_dev), GFP_KERNEL);
  	if (!vpci_dev)
  		return -ENOMEM;
  
  	mutex_init(&vpci_dev->lock);
  
  	for (slot = 0; slot < PCI_SLOT_MAX; slot++)
  		INIT_LIST_HEAD(&vpci_dev->dev_list[slot]);
  
  	pdev->pci_dev_data = vpci_dev;
  
  	return 0;
  }
  
  static int __xen_pcibk_publish_pci_roots(struct xen_pcibk_device *pdev,
  					 publish_pci_root_cb publish_cb)
  {
  	/* The Virtual PCI bus has only one root */
  	return publish_cb(pdev, 0, 0);
  }
  
  static void __xen_pcibk_release_devices(struct xen_pcibk_device *pdev)
  {
  	int slot;
  	struct vpci_dev_data *vpci_dev = pdev->pci_dev_data;
  
  	for (slot = 0; slot < PCI_SLOT_MAX; slot++) {
  		struct pci_dev_entry *e, *tmp;
  		list_for_each_entry_safe(e, tmp, &vpci_dev->dev_list[slot],
  					 list) {
  			struct pci_dev *dev = e->dev;
  			list_del(&e->list);
  			device_lock(&dev->dev);
  			pcistub_put_pci_dev(dev);
  			device_unlock(&dev->dev);
  			kfree(e);
  		}
  	}
  
  	kfree(vpci_dev);
  	pdev->pci_dev_data = NULL;
  }
  
  static int __xen_pcibk_get_pcifront_dev(struct pci_dev *pcidev,
  					struct xen_pcibk_device *pdev,
  					unsigned int *domain, unsigned int *bus,
  					unsigned int *devfn)
  {
  	struct pci_dev_entry *entry;
  	struct pci_dev *dev = NULL;
  	struct vpci_dev_data *vpci_dev = pdev->pci_dev_data;
  	int found = 0, slot;
  
  	mutex_lock(&vpci_dev->lock);
  	for (slot = 0; slot < PCI_SLOT_MAX; slot++) {
  		list_for_each_entry(entry,
  			    &vpci_dev->dev_list[slot],
  			    list) {
  			dev = entry->dev;
  			if (dev && dev->bus->number == pcidev->bus->number
  				&& pci_domain_nr(dev->bus) ==
  					pci_domain_nr(pcidev->bus)
  				&& dev->devfn == pcidev->devfn) {
  				found = 1;
  				*domain = 0;
  				*bus = 0;
  				*devfn = PCI_DEVFN(slot,
  					 PCI_FUNC(pcidev->devfn));
  			}
  		}
  	}
  	mutex_unlock(&vpci_dev->lock);
  	return found;
  }
  
  const struct xen_pcibk_backend xen_pcibk_vpci_backend = {
  	.name		= "vpci",
  	.init		= __xen_pcibk_init_devices,
  	.free		= __xen_pcibk_release_devices,
  	.find		= __xen_pcibk_get_pcifront_dev,
  	.publish	= __xen_pcibk_publish_pci_roots,
  	.release	= __xen_pcibk_release_pci_dev,
  	.add		= __xen_pcibk_add_pci_dev,
  	.get		= __xen_pcibk_get_pci_dev,
  };