/*
   * helpers for managing a buffer for many packets
   *
   * Copyright (c) Clemens Ladisch <clemens@ladisch.de>
   * Licensed under the terms of the GNU General Public License, version 2.
   */
  
  #include <linux/firewire.h>

  #include <linux/export.h>

  #include <linux/slab.h>
  #include "packets-buffer.h"
  
  /**
   * iso_packets_buffer_init - allocates the memory for packets
   * @b: the buffer structure to initialize
   * @unit: the device at the other end of the stream
   * @count: the number of packets
   * @packet_size: the (maximum) size of a packet, in bytes
   * @direction: %DMA_TO_DEVICE or %DMA_FROM_DEVICE
   */
  int iso_packets_buffer_init(struct iso_packets_buffer *b, struct fw_unit *unit,
  			    unsigned int count, unsigned int packet_size,
  			    enum dma_data_direction direction)
  {
  	unsigned int packets_per_page, pages;
  	unsigned int i, page_index, offset_in_page;
  	void *p;
  	int err;
  
  	b->packets = kmalloc(count * sizeof(*b->packets), GFP_KERNEL);
  	if (!b->packets) {
  		err = -ENOMEM;
  		goto error;
  	}
  
  	packet_size = L1_CACHE_ALIGN(packet_size);
  	packets_per_page = PAGE_SIZE / packet_size;
  	if (WARN_ON(!packets_per_page)) {
  		err = -EINVAL;
  		goto error;
  	}
  	pages = DIV_ROUND_UP(count, packets_per_page);
  
  	err = fw_iso_buffer_init(&b->iso_buffer, fw_parent_device(unit)->card,
  				 pages, direction);
  	if (err < 0)
  		goto err_packets;
  
  	for (i = 0; i < count; ++i) {
  		page_index = i / packets_per_page;
  		p = page_address(b->iso_buffer.pages[page_index]);
  		offset_in_page = (i % packets_per_page) * packet_size;
  		b->packets[i].buffer = p + offset_in_page;
  		b->packets[i].offset = page_index * PAGE_SIZE + offset_in_page;
  	}
  
  	return 0;
  
  err_packets:
  	kfree(b->packets);
  error:
  	return err;
  }

  EXPORT_SYMBOL(iso_packets_buffer_init);

  
  /**
   * iso_packets_buffer_destroy - frees packet buffer resources
   * @b: the buffer structure to free
   * @unit: the device at the other end of the stream
   */
  void iso_packets_buffer_destroy(struct iso_packets_buffer *b,
  				struct fw_unit *unit)
  {
  	fw_iso_buffer_destroy(&b->iso_buffer, fw_parent_device(unit)->card);
  	kfree(b->packets);
  }

  EXPORT_SYMBOL(iso_packets_buffer_destroy);