/*
   * Ultra Wide Band
   * DRP availability management
   *
   * Copyright (C) 2005-2006 Intel Corporation
   * Reinette Chatre <reinette.chatre@intel.com>
   * Copyright (C) 2008 Cambridge Silicon Radio Ltd.
   *
   * 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, see <http://www.gnu.org/licenses/>.
   *
   *
   * Manage DRP Availability (the MAS available for DRP
   * reservations). Thus:
   *
   * - Handle DRP Availability Change notifications
   *
   * - Allow the reservation manager to indicate MAS reserved/released
   *   by local (owned by/targeted at the radio controller)
   *   reservations.
   *
   * - Based on the two sources above, generate a DRP Availability IE to
   *   be included in the beacon.
   *
   * See also the documentation for struct uwb_drp_avail.
   */
  
  #include <linux/errno.h>
  #include <linux/module.h>
  #include <linux/device.h>
  #include <linux/bitmap.h>
  #include "uwb-internal.h"
  
  /**
   * uwb_drp_avail_init - initialize an RC's MAS availability
   *
   * All MAS are available initially.  The RC will inform use which
   * slots are used for the BP (it may change in size).
   */
  void uwb_drp_avail_init(struct uwb_rc *rc)
  {
  	bitmap_fill(rc->drp_avail.global, UWB_NUM_MAS);
  	bitmap_fill(rc->drp_avail.local, UWB_NUM_MAS);
  	bitmap_fill(rc->drp_avail.pending, UWB_NUM_MAS);
  }
  
  /*
   * Determine MAS available for new local reservations.
   *
   * avail = global & local & pending
   */
  void uwb_drp_available(struct uwb_rc *rc, struct uwb_mas_bm *avail)
  {
  	bitmap_and(avail->bm, rc->drp_avail.global, rc->drp_avail.local, UWB_NUM_MAS);
  	bitmap_and(avail->bm, avail->bm, rc->drp_avail.pending, UWB_NUM_MAS);
  }
  
  /**
   * uwb_drp_avail_reserve_pending - reserve MAS for a new reservation
   * @rc: the radio controller
   * @mas: the MAS to reserve
   *
   * Returns 0 on success, or -EBUSY if the MAS requested aren't available.
   */
  int uwb_drp_avail_reserve_pending(struct uwb_rc *rc, struct uwb_mas_bm *mas)
  {
  	struct uwb_mas_bm avail;
  
  	uwb_drp_available(rc, &avail);
  	if (!bitmap_subset(mas->bm, avail.bm, UWB_NUM_MAS))
  		return -EBUSY;
  
  	bitmap_andnot(rc->drp_avail.pending, rc->drp_avail.pending, mas->bm, UWB_NUM_MAS);
  	return 0;
  }
  
  /**
   * uwb_drp_avail_reserve - reserve MAS for an established reservation
   * @rc: the radio controller
   * @mas: the MAS to reserve
   */
  void uwb_drp_avail_reserve(struct uwb_rc *rc, struct uwb_mas_bm *mas)
  {
  	bitmap_or(rc->drp_avail.pending, rc->drp_avail.pending, mas->bm, UWB_NUM_MAS);
  	bitmap_andnot(rc->drp_avail.local, rc->drp_avail.local, mas->bm, UWB_NUM_MAS);
  	rc->drp_avail.ie_valid = false;
  }
  
  /**
   * uwb_drp_avail_release - release MAS from a pending or established reservation
   * @rc: the radio controller
   * @mas: the MAS to release
   */
  void uwb_drp_avail_release(struct uwb_rc *rc, struct uwb_mas_bm *mas)
  {
  	bitmap_or(rc->drp_avail.local, rc->drp_avail.local, mas->bm, UWB_NUM_MAS);
  	bitmap_or(rc->drp_avail.pending, rc->drp_avail.pending, mas->bm, UWB_NUM_MAS);
  	rc->drp_avail.ie_valid = false;
  	uwb_rsv_handle_drp_avail_change(rc);
  }
  
  /**
   * uwb_drp_avail_ie_update - update the DRP Availability IE
   * @rc: the radio controller
   *
   * avail = global & local
   */
  void uwb_drp_avail_ie_update(struct uwb_rc *rc)
  {
  	struct uwb_mas_bm avail;
  
  	bitmap_and(avail.bm, rc->drp_avail.global, rc->drp_avail.local, UWB_NUM_MAS);
  
  	rc->drp_avail.ie.hdr.element_id = UWB_IE_DRP_AVAILABILITY;
  	rc->drp_avail.ie.hdr.length = UWB_NUM_MAS / 8;
  	uwb_mas_bm_copy_le(rc->drp_avail.ie.bmp, &avail);
  	rc->drp_avail.ie_valid = true;
  }
  
  /**
   * Create an unsigned long from a buffer containing a byte stream.
   *
   * @array: pointer to buffer
   * @itr:   index of buffer from where we start
   * @len:   the buffer's remaining size may not be exact multiple of
   *         sizeof(unsigned long), @len is the length of buffer that needs
   *         to be converted. This will be sizeof(unsigned long) or smaller
   *         (BUG if not). If it is smaller then we will pad the remaining
   *         space of the result with zeroes.
   */
  static
  unsigned long get_val(u8 *array, size_t itr, size_t len)
  {
  	unsigned long val = 0;
  	size_t top = itr + len;
  
  	BUG_ON(len > sizeof(val));
  
  	while (itr < top) {
  		val <<= 8;
  		val |= array[top - 1];
  		top--;
  	}
  	val <<= 8 * (sizeof(val) - len); /* padding */
  	return val;
  }
  
  /**
   * Initialize bitmap from data buffer.
   *
   * The bitmap to be converted could come from a IE, for example a
   * DRP Availability IE.
   * From ECMA-368 1.0 [16.8.7]: "
   * octets: 1            1               N * (0 to 32)
   *         Element ID   Length (=N)     DRP Availability Bitmap
   *
   * The DRP Availability Bitmap field is up to 256 bits long, one
   * bit for each MAS in the superframe, where the least-significant
   * bit of the field corresponds to the first MAS in the superframe
   * and successive bits correspond to successive MASs."
   *
   * The DRP Availability bitmap is in octets from 0 to 32, so octet
   * 32 contains bits for MAS 1-8, etc. If the bitmap is smaller than 32
   * octets, the bits in octets not included at the end of the bitmap are
   * treated as zero. In this case (when the bitmap is smaller than 32
   * octets) the MAS represented range from MAS 1 to MAS (size of bitmap)
   * with the last octet still containing bits for MAS 1-8, etc.
   *
   * For example:
   * F00F0102 03040506 0708090A 0B0C0D0E 0F010203
   * ^^^^
   * ||||
   * ||||
   * |||\LSB of byte is MAS 9
   * ||\MSB of byte is MAS 16
   * |\LSB of first byte is MAS 1
   * \ MSB of byte is MAS 8
   *
   * An example of this encoding can be found in ECMA-368 Annex-D [Table D.11]
   *
   * The resulting bitmap will have the following mapping:
   *	bit position 0 == MAS 1
   *	bit position 1 == MAS 2
   *	...
   *	bit position (UWB_NUM_MAS - 1) == MAS UWB_NUM_MAS
   *
   * @bmp_itr:	pointer to bitmap (can be declared with DECLARE_BITMAP)
   * @buffer:	pointer to buffer containing bitmap data in big endian
   *              format (MSB first)
   * @buffer_size:number of bytes with which bitmap should be initialized
   */
  static
  void buffer_to_bmp(unsigned long *bmp_itr, void *_buffer,
  		   size_t buffer_size)
  {
  	u8 *buffer = _buffer;
  	size_t itr, len;
  	unsigned long val;
  
  	itr = 0;
  	while (itr < buffer_size) {
  		len = buffer_size - itr >= sizeof(val) ?
  			sizeof(val) : buffer_size - itr;
  		val = get_val(buffer, itr, len);
  		bmp_itr[itr / sizeof(val)] = val;
  		itr += sizeof(val);
  	}
  }
  
  
  /**
   * Extract DRP Availability bitmap from the notification.
   *
   * The notification that comes in contains a bitmap of (UWB_NUM_MAS / 8) bytes
   * We convert that to our internal representation.
   */
  static
  int uwbd_evt_get_drp_avail(struct uwb_event *evt, unsigned long *bmp)
  {
  	struct device *dev = &evt->rc->uwb_dev.dev;
  	struct uwb_rc_evt_drp_avail *drp_evt;
  	int result = -EINVAL;
  
  	/* Is there enough data to decode the event? */
  	if (evt->notif.size < sizeof(*drp_evt)) {
  		dev_err(dev, "DRP Availability Change: Not enough "
  			"data to decode event [%zu bytes, %zu "
  			"needed]
  ", evt->notif.size, sizeof(*drp_evt));
  		goto error;
  	}
  	drp_evt = container_of(evt->notif.rceb, struct uwb_rc_evt_drp_avail, rceb);
  	buffer_to_bmp(bmp, drp_evt->bmp, UWB_NUM_MAS/8);
  	result = 0;
  error:
  	return result;
  }
  
  
  /**
   * Process an incoming DRP Availability notification.
   *
   * @evt:	Event information (packs the actual event data, which
   *              radio controller it came to, etc).
   *
   * @returns:    0 on success (so uwbd() frees the event buffer), < 0
   *              on error.
   *
   * According to ECMA-368 1.0 [16.8.7], bits set to ONE indicate that
   * the MAS slot is available, bits set to ZERO indicate that the slot
   * is busy.
   *
   * So we clear available slots, we set used slots :)
   *
   * The notification only marks non-availability based on the BP and
   * received DRP IEs that are not for this radio controller.  A copy of
   * this bitmap is needed to generate the real availability (which
   * includes local and pending reservations).
   *
   * The DRP Availability IE that this radio controller emits will need
   * to be updated.
   */
  int uwbd_evt_handle_rc_drp_avail(struct uwb_event *evt)
  {
  	int result;
  	struct uwb_rc *rc = evt->rc;
  	DECLARE_BITMAP(bmp, UWB_NUM_MAS);
  
  	result = uwbd_evt_get_drp_avail(evt, bmp);
  	if (result < 0)
  		return result;
  
  	mutex_lock(&rc->rsvs_mutex);
  	bitmap_copy(rc->drp_avail.global, bmp, UWB_NUM_MAS);
  	rc->drp_avail.ie_valid = false;
  	uwb_rsv_handle_drp_avail_change(rc);
  	mutex_unlock(&rc->rsvs_mutex);
  
  	uwb_rsv_sched_update(rc);
  
  	return 0;
  }