sound/firewire/fcp.c

   1 /*
   2  * Function Control Protocol (IEC 61883-1) 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/device.h>
   9 #include <linux/firewire.h>
  10 #include <linux/firewire-constants.h>
  11 #include <linux/list.h>
  12 #include <linux/module.h>
  13 #include <linux/sched.h>
  14 #include <linux/spinlock.h>
  15 #include <linux/wait.h>
  16 #include <linux/delay.h>
  17 #include "fcp.h"
  18 #include "lib.h"
  19
  20 #define CTS_AVC 0x00
  21
  22 #define ERROR_RETRIES   3
  23 #define ERROR_DELAY_MS  5
  24 #define FCP_TIMEOUT_MS  125
  25
  26 static DEFINE_SPINLOCK(transactions_lock);
  27 static LIST_HEAD(transactions);
  28
  29 enum fcp_state {
  30         STATE_PENDING,
  31         STATE_BUS_RESET,
  32         STATE_COMPLETE,
  33 };
  34
  35 struct fcp_transaction {
  36         struct list_head list;
  37         struct fw_unit *unit;
  38         void *response_buffer;
  39         unsigned int response_size;
  40         unsigned int response_match_bytes;
  41         enum fcp_state state;
  42         wait_queue_head_t wait;
  43 };
  44
  45 /**
  46  * fcp_avc_transaction - send an AV/C command and wait for its response
  47  * @unit: a unit on the target device
  48  * @command: a buffer containing the command frame; must be DMA-able
  49  * @command_size: the size of @command
  50  * @response: a buffer for the response frame
  51  * @response_size: the maximum size of @response
  52  * @response_match_bytes: a bitmap specifying the bytes used to detect the
  53  *                        correct response frame
  54  *
  55  * This function sends a FCP command frame to the target and waits for the
  56  * corresponding response frame to be returned.
  57  *
  58  * Because it is possible for multiple FCP transactions to be active at the
  59  * same time, the correct response frame is detected by the value of certain
  60  * bytes.  These bytes must be set in @response before calling this function,
  61  * and the corresponding bits must be set in @response_match_bytes.
  62  *
  63  * @command and @response can point to the same buffer.
  64  *
  65  * Asynchronous operation (INTERIM, NOTIFY) is not supported at the moment.
  66  *
  67  * Returns the actual size of the response frame, or a negative error code.
  68  */
  69 int fcp_avc_transaction(struct fw_unit *unit,
  70                         const void *command, unsigned int command_size,
  71                         void *response, unsigned int response_size,
  72                         unsigned int response_match_bytes)
  73 {
  74         struct fcp_transaction t;
  75         int tcode, ret, tries = 0;
  76
  77         t.unit = unit;
  78         t.response_buffer = response;
  79         t.response_size = response_size;
  80         t.response_match_bytes = response_match_bytes;
  81         t.state = STATE_PENDING;
  82         init_waitqueue_head(&t.wait);
  83
  84         spin_lock_irq(&transactions_lock);
  85         list_add_tail(&t.list, &transactions);
  86         spin_unlock_irq(&transactions_lock);
  87
  88         for (;;) {
  89                 tcode = command_size == 4 ? TCODE_WRITE_QUADLET_REQUEST
  90                                           : TCODE_WRITE_BLOCK_REQUEST;
  91                 ret = snd_fw_transaction(t.unit, tcode,
  92                                          CSR_REGISTER_BASE + CSR_FCP_COMMAND,
  93                                          (void *)command, command_size);
  94                 if (ret < 0)
  95                         break;
  96
  97                 wait_event_timeout(t.wait, t.state != STATE_PENDING,
  98                                    msecs_to_jiffies(FCP_TIMEOUT_MS));
  99
 100                 if (t.state == STATE_COMPLETE) {
 101                         ret = t.response_size;
 102                         break;
 103                 } else if (t.state == STATE_BUS_RESET) {
 104                         msleep(ERROR_DELAY_MS);
 105                 } else if (++tries >= ERROR_RETRIES) {
 106                         dev_err(&t.unit->device, "FCP command timed out\n");
 107                         ret = -EIO;
 108                         break;
 109                 }
 110         }
 111
 112         spin_lock_irq(&transactions_lock);
 113         list_del(&t.list);
 114         spin_unlock_irq(&transactions_lock);
 115
 116         return ret;
 117 }
 118 EXPORT_SYMBOL(fcp_avc_transaction);
 119
 120 /**
 121  * fcp_bus_reset - inform the target handler about a bus reset
 122  * @unit: the unit that might be used by fcp_avc_transaction()
 123  *
 124  * This function must be called from the driver's .update handler to inform
 125  * the FCP transaction handler that a bus reset has happened.  Any pending FCP
 126  * transactions are retried.
 127  */
 128 void fcp_bus_reset(struct fw_unit *unit)
 129 {
 130         struct fcp_transaction *t;
 131
 132         spin_lock_irq(&transactions_lock);
 133         list_for_each_entry(t, &transactions, list) {
 134                 if (t->unit == unit &&
 135                     t->state == STATE_PENDING) {
 136                         t->state = STATE_BUS_RESET;
 137                         wake_up(&t->wait);
 138                 }
 139         }
 140         spin_unlock_irq(&transactions_lock);
 141 }
 142 EXPORT_SYMBOL(fcp_bus_reset);
 143
 144 /* checks whether the response matches the masked bytes in response_buffer */
 145 static bool is_matching_response(struct fcp_transaction *transaction,
 146                                  const void *response, size_t length)
 147 {
 148         const u8 *p1, *p2;
 149         unsigned int mask, i;
 150
 151         p1 = response;
 152         p2 = transaction->response_buffer;
 153         mask = transaction->response_match_bytes;
 154
 155         for (i = 0; ; ++i) {
 156                 if ((mask & 1) && p1[i] != p2[i])
 157                         return false;
 158                 mask >>= 1;
 159                 if (!mask)
 160                         return true;
 161                 if (--length == 0)
 162                         return false;
 163         }
 164 }
 165
 166 static void fcp_response(struct fw_card *card, struct fw_request *request,
 167                          int tcode, int destination, int source,
 168                          int generation, unsigned long long offset,
 169                          void *data, size_t length, void *callback_data)
 170 {
 171         struct fcp_transaction *t;
 172         unsigned long flags;
 173
 174         if (length < 1 || (*(const u8 *)data & 0xf0) != CTS_AVC)
 175                 return;
 176
 177         spin_lock_irqsave(&transactions_lock, flags);
 178         list_for_each_entry(t, &transactions, list) {
 179                 struct fw_device *device = fw_parent_device(t->unit);
 180                 if (device->card != card ||
 181                     device->generation != generation)
 182                         continue;
 183                 smp_rmb(); /* node_id vs. generation */
 184                 if (device->node_id != source)
 185                         continue;
 186
 187                 if (t->state == STATE_PENDING &&
 188                     is_matching_response(t, data, length)) {
 189                         t->state = STATE_COMPLETE;
 190                         t->response_size = min((unsigned int)length,
 191                                                t->response_size);
 192                         memcpy(t->response_buffer, data, t->response_size);
 193                         wake_up(&t->wait);
 194                 }
 195         }
 196         spin_unlock_irqrestore(&transactions_lock, flags);
 197 }
 198
 199 static struct fw_address_handler response_register_handler = {
 200         .length = 0x200,
 201         .address_callback = fcp_response,
 202 };
 203
 204 static int __init fcp_module_init(void)
 205 {
 206         static const struct fw_address_region response_register_region = {
 207                 .start = CSR_REGISTER_BASE + CSR_FCP_RESPONSE,
 208                 .end = CSR_REGISTER_BASE + CSR_FCP_END,
 209         };
 210
 211         fw_core_add_address_handler(&response_register_handler,
 212                                     &response_register_region);
 213
 214         return 0;
 215 }
 216
 217 static void __exit fcp_module_exit(void)
 218 {
 219         WARN_ON(!list_empty(&transactions));
 220         fw_core_remove_address_handler(&response_register_handler);
 221 }
 222
 223 module_init(fcp_module_init);
 224 module_exit(fcp_module_exit);