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