/*
   * Ultra Wide Band
   * Neighborhood Management Daemon
   *
   * Copyright (C) 2005-2006 Intel Corporation
   * Inaky Perez-Gonzalez <inaky.perez-gonzalez@intel.com>
   *
   * This program is free software; you can redistribute it and/or
   * modify it under the terms of the GNU General Public License version
   * 2 as published by the Free Software Foundation.
   *
   * 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 Street, Fifth Floor, Boston, MA
   * 02110-1301, USA.
   *
   *
   * This daemon takes care of maintaing information that describes the
   * UWB neighborhood that the radios in this machine can see. It also
   * keeps a tab of which devices are visible, makes sure each HC sits
   * on a different channel to avoid interfering, etc.
   *
   * Different drivers (radio controller, device, any API in general)
   * communicate with this daemon through an event queue. Daemon wakes
   * up, takes a list of events and handles them one by one; handling
   * function is extracted from a table based on the event's type and
   * subtype. Events are freed only if the handling function says so.
   *
   *   . Lock protecting the event list has to be an spinlock and locked
   *     with IRQSAVE because it might be called from an interrupt
   *     context (ie: when events arrive and the notification drops
   *     down from the ISR).
   *
   *   . UWB radio controller drivers queue events to the daemon using
   *     uwbd_event_queue(). They just get the event, chew it to make it
   *     look like UWBD likes it and pass it in a buffer allocated with
   *     uwb_event_alloc().
   *
   * EVENTS
   *
   * Events have a type, a subtype, a length, some other stuff and the
   * data blob, which depends on the event. The header is 'struct
   * uwb_event'; for payloads, see 'struct uwbd_evt_*'.
   *
   * EVENT HANDLER TABLES
   *
   * To find a handling function for an event, the type is used to index
   * a subtype-table in the type-table. The subtype-table is indexed
   * with the subtype to get the function that handles the event. Start
   * with the main type-table 'uwbd_evt_type_handler'.
   *
   * DEVICES
   *
   * Devices are created when a bunch of beacons have been received and
   * it is stablished that the device has stable radio presence. CREATED
   * only, not configured. Devices are ONLY configured when an
   * Application-Specific IE Probe is receieved, in which the device
   * declares which Protocol ID it groks. Then the device is CONFIGURED
   * (and the driver->probe() stuff of the device model is invoked).
   *
   * Devices are considered disconnected when a certain number of
   * beacons are not received in an amount of time.
   *
   * Handler functions are called normally uwbd_evt_handle_*().
   */
  #include <linux/kthread.h>
  #include <linux/slab.h>
  #include <linux/module.h>
  #include <linux/freezer.h>
  
  #include "uwb-internal.h"
  
  /*
   * UWBD Event handler function signature
   *
   * Return !0 if the event needs not to be freed (ie the handler
   * takes/took care of it). 0 means the daemon code will free the
   * event.
   *
   * @evt->rc is already referenced and guaranteed to exist. See
   * uwb_evt_handle().
   */
  typedef int (*uwbd_evt_handler_f)(struct uwb_event *);
  
  /**
   * Properties of a UWBD event
   *
   * @handler:    the function that will handle this event
   * @name:       text name of event
   */
  struct uwbd_event {
  	uwbd_evt_handler_f handler;
  	const char *name;
  };
  
  /* Table of handlers for and properties of the UWBD Radio Control Events */
  static struct uwbd_event uwbd_urc_events[] = {
  	[UWB_RC_EVT_IE_RCV] = {
  		.handler = uwbd_evt_handle_rc_ie_rcv,
  		.name = "IE_RECEIVED"
  	},
  	[UWB_RC_EVT_BEACON] = {
  		.handler = uwbd_evt_handle_rc_beacon,
  		.name = "BEACON_RECEIVED"
  	},
  	[UWB_RC_EVT_BEACON_SIZE] = {
  		.handler = uwbd_evt_handle_rc_beacon_size,
  		.name = "BEACON_SIZE_CHANGE"
  	},
  	[UWB_RC_EVT_BPOIE_CHANGE] = {
  		.handler = uwbd_evt_handle_rc_bpoie_change,
  		.name = "BPOIE_CHANGE"
  	},
  	[UWB_RC_EVT_BP_SLOT_CHANGE] = {
  		.handler = uwbd_evt_handle_rc_bp_slot_change,
  		.name = "BP_SLOT_CHANGE"
  	},
  	[UWB_RC_EVT_DRP_AVAIL] = {
  		.handler = uwbd_evt_handle_rc_drp_avail,
  		.name = "DRP_AVAILABILITY_CHANGE"
  	},
  	[UWB_RC_EVT_DRP] = {
  		.handler = uwbd_evt_handle_rc_drp,
  		.name = "DRP"
  	},
  	[UWB_RC_EVT_DEV_ADDR_CONFLICT] = {
  		.handler = uwbd_evt_handle_rc_dev_addr_conflict,
  		.name = "DEV_ADDR_CONFLICT",
  	},
  };
  
  
  
  struct uwbd_evt_type_handler {
  	const char *name;
  	struct uwbd_event *uwbd_events;
  	size_t size;
  };
  
  /* Table of handlers for each UWBD Event type. */
  static struct uwbd_evt_type_handler uwbd_urc_evt_type_handlers[] = {
  	[UWB_RC_CET_GENERAL] = {
  		.name        = "URC",
  		.uwbd_events = uwbd_urc_events,
  		.size        = ARRAY_SIZE(uwbd_urc_events),
  	},
  };
  
  static const struct uwbd_event uwbd_message_handlers[] = {
  	[UWB_EVT_MSG_RESET] = {
  		.handler = uwbd_msg_handle_reset,
  		.name = "reset",
  	},
  };
  
  /*
   * Handle an URC event passed to the UWB Daemon
   *
   * @evt: the event to handle
   * @returns: 0 if the event can be kfreed, !0 on the contrary
   *           (somebody else took ownership) [coincidentally, returning
   *           a <0 errno code will free it :)].
   *
   * Looks up the two indirection tables (one for the type, one for the
   * subtype) to decide which function handles it and then calls the
   * handler.
   *
   * The event structure passed to the event handler has the radio
   * controller in @evt->rc referenced. The reference will be dropped
   * once the handler returns, so if it needs it for longer (async),
   * it'll need to take another one.
   */
  static
  int uwbd_event_handle_urc(struct uwb_event *evt)
  {
  	int result = -EINVAL;
  	struct uwbd_evt_type_handler *type_table;
  	uwbd_evt_handler_f handler;
  	u8 type, context;
  	u16 event;
  
  	type = evt->notif.rceb->bEventType;
  	event = le16_to_cpu(evt->notif.rceb->wEvent);
  	context = evt->notif.rceb->bEventContext;
  
  	if (type >= ARRAY_SIZE(uwbd_urc_evt_type_handlers))
  		goto out;
  	type_table = &uwbd_urc_evt_type_handlers[type];
  	if (type_table->uwbd_events == NULL)
  		goto out;
  	if (event >= type_table->size)
  		goto out;
  	handler = type_table->uwbd_events[event].handler;
  	if (handler == NULL)
  		goto out;
  
  	result = (*handler)(evt);
  out:
  	if (result < 0)
  		dev_err(&evt->rc->uwb_dev.dev,
  			"UWBD: event 0x%02x/%04x/%02x, handling failed: %d
  ",
  			type, event, context, result);
  	return result;
  }
  
  static void uwbd_event_handle_message(struct uwb_event *evt)
  {
  	struct uwb_rc *rc;
  	int result;
  
  	rc = evt->rc;
  
  	if (evt->message < 0 || evt->message >= ARRAY_SIZE(uwbd_message_handlers)) {
  		dev_err(&rc->uwb_dev.dev, "UWBD: invalid message type %d
  ", evt->message);
  		return;
  	}
  
  	result = uwbd_message_handlers[evt->message].handler(evt);
  	if (result < 0)
  		dev_err(&rc->uwb_dev.dev, "UWBD: '%s' message failed: %d
  ",
  			uwbd_message_handlers[evt->message].name, result);
  }
  
  static void uwbd_event_handle(struct uwb_event *evt)
  {
  	struct uwb_rc *rc;
  	int should_keep;
  
  	rc = evt->rc;
  
  	if (rc->ready) {
  		switch (evt->type) {
  		case UWB_EVT_TYPE_NOTIF:
  			should_keep = uwbd_event_handle_urc(evt);
  			if (should_keep <= 0)
  				kfree(evt->notif.rceb);
  			break;
  		case UWB_EVT_TYPE_MSG:
  			uwbd_event_handle_message(evt);
  			break;
  		default:
  			dev_err(&rc->uwb_dev.dev, "UWBD: invalid event type %d
  ", evt->type);
  			break;
  		}
  	}
  
  	__uwb_rc_put(rc);	/* for the __uwb_rc_get() in uwb_rc_notif_cb() */
  }
  
  /**
   * UWB Daemon
   *
   * Listens to all UWB notifications and takes care to track the state
   * of the UWB neighbourhood for the kernel. When we do a run, we
   * spinlock, move the list to a private copy and release the
   * lock. Hold it as little as possible. Not a conflict: it is
   * guaranteed we own the events in the private list.
   *
   * FIXME: should change so we don't have a 1HZ timer all the time, but
   *        only if there are devices.
   */
  static int uwbd(void *param)
  {
  	struct uwb_rc *rc = param;
  	unsigned long flags;
  	struct uwb_event *evt;
  	int should_stop = 0;
  
  	while (1) {
  		wait_event_interruptible_timeout(
  			rc->uwbd.wq,
  			!list_empty(&rc->uwbd.event_list)
  			  || (should_stop = kthread_should_stop()),
  			HZ);
  		if (should_stop)
  			break;
  		try_to_freeze();
  
  		spin_lock_irqsave(&rc->uwbd.event_list_lock, flags);
  		if (!list_empty(&rc->uwbd.event_list)) {
  			evt = list_first_entry(&rc->uwbd.event_list, struct uwb_event, list_node);
  			list_del(&evt->list_node);
  		} else
  			evt = NULL;
  		spin_unlock_irqrestore(&rc->uwbd.event_list_lock, flags);
  
  		if (evt) {
  			uwbd_event_handle(evt);
  			kfree(evt);
  		}
  
  		uwb_beca_purge(rc);	/* Purge devices that left */
  	}
  	return 0;
  }
  
  
  /** Start the UWB daemon */
  void uwbd_start(struct uwb_rc *rc)
  {
  	rc->uwbd.task = kthread_run(uwbd, rc, "uwbd");
  	if (rc->uwbd.task == NULL)
  		printk(KERN_ERR "UWB: Cannot start management daemon; "
  		       "UWB won't work
  ");
  	else
  		rc->uwbd.pid = rc->uwbd.task->pid;
  }
  
  /* Stop the UWB daemon and free any unprocessed events */
  void uwbd_stop(struct uwb_rc *rc)
  {
  	kthread_stop(rc->uwbd.task);
  	uwbd_flush(rc);
  }
  
  /*
   * Queue an event for the management daemon
   *
   * When some lower layer receives an event, it uses this function to
   * push it forward to the UWB daemon.
   *
   * Once you pass the event, you don't own it any more, but the daemon
   * does. It will uwb_event_free() it when done, so make sure you
   * uwb_event_alloc()ed it or bad things will happen.
   *
   * If the daemon is not running, we just free the event.
   */
  void uwbd_event_queue(struct uwb_event *evt)
  {
  	struct uwb_rc *rc = evt->rc;
  	unsigned long flags;
  
  	spin_lock_irqsave(&rc->uwbd.event_list_lock, flags);
  	if (rc->uwbd.pid != 0) {
  		list_add(&evt->list_node, &rc->uwbd.event_list);
  		wake_up_all(&rc->uwbd.wq);
  	} else {
  		__uwb_rc_put(evt->rc);
  		if (evt->type == UWB_EVT_TYPE_NOTIF)
  			kfree(evt->notif.rceb);
  		kfree(evt);
  	}
  	spin_unlock_irqrestore(&rc->uwbd.event_list_lock, flags);
  	return;
  }
  
  void uwbd_flush(struct uwb_rc *rc)
  {
  	struct uwb_event *evt, *nxt;
  
  	spin_lock_irq(&rc->uwbd.event_list_lock);
  	list_for_each_entry_safe(evt, nxt, &rc->uwbd.event_list, list_node) {
  		if (evt->rc == rc) {
  			__uwb_rc_put(rc);
  			list_del(&evt->list_node);
  			if (evt->type == UWB_EVT_TYPE_NOTIF)
  				kfree(evt->notif.rceb);
  			kfree(evt);
  		}
  	}
  	spin_unlock_irq(&rc->uwbd.event_list_lock);
  }