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/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  */
  20 int 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
  58 err_packets:
  59         kfree(b->packets);
  60 error:
  61         return err;
  62 }
  63 EXPORT_SYMBOL(iso_packets_buffer_init);
  64
  65 /**
  66  * iso_packets_buffer_destroy - frees packet buffer resources
  67  * @b: the buffer structure to free
  68  * @unit: the device at the other end of the stream
  69  */
  70 void iso_packets_buffer_destroy(struct iso_packets_buffer *b,
  71                                 struct fw_unit *unit)
  72 {
  73         fw_iso_buffer_destroy(&b->iso_buffer, fw_parent_device(unit)->card);
  74         kfree(b->packets);
  75 }
  76 EXPORT_SYMBOL(iso_packets_buffer_destroy);