sound/firewire/lib.c

   1 /*
   2  * miscellaneous helper functions
   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/delay.h>
   9 #include <linux/device.h>
  10 #include <linux/firewire.h>
  11 #include <linux/module.h>
  12 #include "lib.h"
  13
  14 #define ERROR_RETRY_DELAY_MS    5
  15
  16 /**
  17  * snd_fw_transaction - send a request and wait for its completion
  18  * @unit: the driver's unit on the target device
  19  * @tcode: the transaction code
  20  * @offset: the address in the target's address space
  21  * @buffer: input/output data
  22  * @length: length of @buffer
  23  *
  24  * Submits an asynchronous request to the target device, and waits for the
  25  * response.  The node ID and the current generation are derived from @unit.
  26  * On a bus reset or an error, the transaction is retried a few times.
  27  * Returns zero on success, or a negative error code.
  28  */
  29 int snd_fw_transaction(struct fw_unit *unit, int tcode,
  30                        u64 offset, void *buffer, size_t length)
  31 {
  32         struct fw_device *device = fw_parent_device(unit);
  33         int generation, rcode, tries = 0;
  34
  35         for (;;) {
  36                 generation = device->generation;
  37                 smp_rmb(); /* node_id vs. generation */
  38                 rcode = fw_run_transaction(device->card, tcode,
  39                                            device->node_id, generation,
  40                                            device->max_speed, offset,
  41                                            buffer, length);
  42
  43                 if (rcode == RCODE_COMPLETE)
  44                         return 0;
  45
  46                 if (rcode_is_permanent_error(rcode) || ++tries >= 3) {
  47                         dev_err(&unit->device, "transaction failed: %s\n",
  48                                 fw_rcode_string(rcode));
  49                         return -EIO;
  50                 }
  51
  52                 msleep(ERROR_RETRY_DELAY_MS);
  53         }
  54 }
  55 EXPORT_SYMBOL(snd_fw_transaction);
  56
  57 MODULE_DESCRIPTION("FireWire audio helper functions");
  58 MODULE_AUTHOR("Clemens Ladisch <clemens@ladisch.de>");
  59 MODULE_LICENSE("GPL v2");