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    20
  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  * @flags: use %FW_FIXED_GENERATION and add the generation value to attempt the
  24  *         request only in that generation; use %FW_QUIET to suppress error
  25  *         messages
  26  *
  27  * Submits an asynchronous request to the target device, and waits for the
  28  * response.  The node ID and the current generation are derived from @unit.
  29  * On a bus reset or an error, the transaction is retried a few times.
  30  * Returns zero on success, or a negative error code.
  31  */
  32 int snd_fw_transaction(struct fw_unit *unit, int tcode,
  33                        u64 offset, void *buffer, size_t length,
  34                        unsigned int flags)
  35 {
  36         struct fw_device *device = fw_parent_device(unit);
  37         int generation, rcode, tries = 0;
  38
  39         generation = flags & FW_GENERATION_MASK;
  40         for (;;) {
  41                 if (!(flags & FW_FIXED_GENERATION)) {
  42                         generation = device->generation;
  43                         smp_rmb(); /* node_id vs. generation */
  44                 }
  45                 rcode = fw_run_transaction(device->card, tcode,
  46                                            device->node_id, generation,
  47                                            device->max_speed, offset,
  48                                            buffer, length);
  49
  50                 if (rcode == RCODE_COMPLETE)
  51                         return 0;
  52
  53                 if (rcode == RCODE_GENERATION && (flags & FW_FIXED_GENERATION))
  54                         return -EAGAIN;
  55
  56                 if (rcode_is_permanent_error(rcode) || ++tries >= 3) {
  57                         if (!(flags & FW_QUIET))
  58                                 dev_err(&unit->device,
  59                                         "transaction failed: %s\n",
  60                                         fw_rcode_string(rcode));
  61                         return -EIO;
  62                 }
  63
  64                 msleep(ERROR_RETRY_DELAY_MS);
  65         }
  66 }
  67 EXPORT_SYMBOL(snd_fw_transaction);
  68
  69 MODULE_DESCRIPTION("FireWire audio helper functions");
  70 MODULE_AUTHOR("Clemens Ladisch <clemens@ladisch.de>");
  71 MODULE_LICENSE("GPL v2");