LXR linux/sound/firewire/packets-buffer.c

   1/*
   2 * helpers for managing a buffer for many packets
   3 *
   4 * Copyright (c) Clemens Ladisch <clemens@ladisch.de>
   5 * Licensed under the terms of the GNU General Public License, version 2.
   6 */
   7
   8#include <linux/firewire.h>
   9#include <linux/export.h>
  10#include <linux/slab.h>
  11#include "packets-buffer.h"
  12
  13/**
  14 * iso_packets_buffer_init - allocates the memory for packets
  15 * @b: the buffer structure to initialize
  16 * @unit: the device at the other end of the stream
  17 * @count: the number of packets
  18 * @packet_size: the (maximum) size of a packet, in bytes
  19 * @direction: %DMA_TO_DEVICE or %DMA_FROM_DEVICE
  20 */
  21int iso_packets_buffer_init(struct iso_packets_buffer *b, struct fw_unit *unit,
  22                            unsigned int count, unsigned int packet_size,
  23                            enum dma_data_direction direction)
  24{
  25        unsigned int packets_per_page, pages;
  26        unsigned int i, page_index, offset_in_page;
  27        void *p;
  28        int err;
  29
  30        b->packets = kmalloc(count * sizeof(*b->packets), GFP_KERNEL);
  31        if (!b->packets) {
  32                err = -ENOMEM;
  33                goto error;
  34        }
  35
  36        packet_size = L1_CACHE_ALIGN(packet_size);
  37        packets_per_page = PAGE_SIZE / packet_size;
  38        if (WARN_ON(!packets_per_page)) {
  39                err = -EINVAL;
  40                goto error;
  41        }
  42        pages = DIV_ROUND_UP(count, packets_per_page);
  43
  44        err = fw_iso_buffer_init(&b->iso_buffer, fw_parent_device(unit)->card,
  45                                 pages, direction);
  46        if (err < 0)
  47                goto err_packets;
  48
  49        for (i = 0; i < count; ++i) {
  50                page_index = i / packets_per_page;
  51                p = page_address(b->iso_buffer.pages[page_index]);
  52                offset_in_page = (i % packets_per_page) * packet_size;
  53                b->packets[i].buffer = p + offset_in_page;
  54                b->packets[i].offset = page_index * PAGE_SIZE + offset_in_page;
  55        }
  56
  57        return 0;
  58
  59err_packets:
  60        kfree(b->packets);
  61error:
  62        return err;
  63}
  64EXPORT_SYMBOL(iso_packets_buffer_init);
  65
  66/**
  67 * iso_packets_buffer_destroy - frees packet buffer resources
  68 * @b: the buffer structure to free
  69 * @unit: the device at the other end of the stream
  70 */
  71void iso_packets_buffer_destroy(struct iso_packets_buffer *b,
  72                                struct fw_unit *unit)
  73{
  74        fw_iso_buffer_destroy(&b->iso_buffer, fw_parent_device(unit)->card);
  75        kfree(b->packets);
  76}
  77EXPORT_SYMBOL(iso_packets_buffer_destroy);
  78