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         STATE_DEFERRED,
  34 };
  35
  36 struct fcp_transaction {
  37         struct list_head list;
  38         struct fw_unit *unit;
  39         void *response_buffer;
  40         unsigned int response_size;
  41         unsigned int response_match_bytes;
  42         enum fcp_state state;
  43         wait_queue_head_t wait;
  44         bool deferrable;
  45 };
  46
  47 /**
  48  * fcp_avc_transaction - send an AV/C command and wait for its response
  49  * @unit: a unit on the target device
  50  * @command: a buffer containing the command frame; must be DMA-able
  51  * @command_size: the size of @command
  52  * @response: a buffer for the response frame
  53  * @response_size: the maximum size of @response
  54  * @response_match_bytes: a bitmap specifying the bytes used to detect the
  55  *                        correct response frame
  56  *
  57  * This function sends a FCP command frame to the target and waits for the
  58  * corresponding response frame to be returned.
  59  *
  60  * Because it is possible for multiple FCP transactions to be active at the
  61  * same time, the correct response frame is detected by the value of certain
  62  * bytes.  These bytes must be set in @response before calling this function,
  63  * and the corresponding bits must be set in @response_match_bytes.
  64  *
  65  * @command and @response can point to the same buffer.
  66  *
  67  * Asynchronous operation (INTERIM, NOTIFY) is not supported at the moment.
  68  *
  69  * Returns the actual size of the response frame, or a negative error code.
  70  */
  71 int fcp_avc_transaction(struct fw_unit *unit,
  72                         const void *command, unsigned int command_size,
  73                         void *response, unsigned int response_size,
  74                         unsigned int response_match_bytes)
  75 {
  76         struct fcp_transaction t;
  77         int tcode, ret, tries = 0;
  78
  79         t.unit = unit;
  80         t.response_buffer = response;
  81         t.response_size = response_size;
  82         t.response_match_bytes = response_match_bytes;
  83         t.state = STATE_PENDING;
  84         init_waitqueue_head(&t.wait);
  85
  86         if (*(const u8 *)command == 0x00 || *(const u8 *)command == 0x03)
  87                 t.deferrable = true;
  88
  89         spin_lock_irq(&transactions_lock);
  90         list_add_tail(&t.list, &transactions);
  91         spin_unlock_irq(&transactions_lock);
  92
  93         for (;;) {
  94                 tcode = command_size == 4 ? TCODE_WRITE_QUADLET_REQUEST
  95                                           : TCODE_WRITE_BLOCK_REQUEST;
  96                 ret = snd_fw_transaction(t.unit, tcode,
  97                                          CSR_REGISTER_BASE + CSR_FCP_COMMAND,
  98                                          (void *)command, command_size, 0);
  99                 if (ret < 0)
 100                         break;
 101 deferred:
 102                 wait_event_timeout(t.wait, t.state != STATE_PENDING,
 103                                    msecs_to_jiffies(FCP_TIMEOUT_MS));
 104
 105                 if (t.state == STATE_DEFERRED) {
 106                         /*
 107                          * 'AV/C General Specification' define no time limit
 108                          * on command completion once an INTERIM response has
 109                          * been sent. but we promise to finish this function
 110                          * for a caller. Here we use FCP_TIMEOUT_MS for next
 111                          * interval. This is not in the specification.
 112                          */
 113                         t.state = STATE_PENDING;
 114                         goto deferred;
 115                 } else if (t.state == STATE_COMPLETE) {
 116                         ret = t.response_size;
 117                         break;
 118                 } else if (t.state == STATE_BUS_RESET) {
 119                         msleep(ERROR_DELAY_MS);
 120                 } else if (++tries >= ERROR_RETRIES) {
 121                         dev_err(&t.unit->device, "FCP command timed out\n");
 122                         ret = -EIO;
 123                         break;
 124                 }
 125         }
 126
 127         spin_lock_irq(&transactions_lock);
 128         list_del(&t.list);
 129         spin_unlock_irq(&transactions_lock);
 130
 131         return ret;
 132 }
 133 EXPORT_SYMBOL(fcp_avc_transaction);
 134
 135 /**
 136  * fcp_bus_reset - inform the target handler about a bus reset
 137  * @unit: the unit that might be used by fcp_avc_transaction()
 138  *
 139  * This function must be called from the driver's .update handler to inform
 140  * the FCP transaction handler that a bus reset has happened.  Any pending FCP
 141  * transactions are retried.
 142  */
 143 void fcp_bus_reset(struct fw_unit *unit)
 144 {
 145         struct fcp_transaction *t;
 146
 147         spin_lock_irq(&transactions_lock);
 148         list_for_each_entry(t, &transactions, list) {
 149                 if (t->unit == unit &&
 150                     (t->state == STATE_PENDING ||
 151                      t->state == STATE_DEFERRED)) {
 152                         t->state = STATE_BUS_RESET;
 153                         wake_up(&t->wait);
 154                 }
 155         }
 156         spin_unlock_irq(&transactions_lock);
 157 }
 158 EXPORT_SYMBOL(fcp_bus_reset);
 159
 160 /* checks whether the response matches the masked bytes in response_buffer */
 161 static bool is_matching_response(struct fcp_transaction *transaction,
 162                                  const void *response, size_t length)
 163 {
 164         const u8 *p1, *p2;
 165         unsigned int mask, i;
 166
 167         p1 = response;
 168         p2 = transaction->response_buffer;
 169         mask = transaction->response_match_bytes;
 170
 171         for (i = 0; ; ++i) {
 172                 if ((mask & 1) && p1[i] != p2[i])
 173                         return false;
 174                 mask >>= 1;
 175                 if (!mask)
 176                         return true;
 177                 if (--length == 0)
 178                         return false;
 179         }
 180 }
 181
 182 static void fcp_response(struct fw_card *card, struct fw_request *request,
 183                          int tcode, int destination, int source,
 184                          int generation, unsigned long long offset,
 185                          void *data, size_t length, void *callback_data)
 186 {
 187         struct fcp_transaction *t;
 188         unsigned long flags;
 189
 190         if (length < 1 || (*(const u8 *)data & 0xf0) != CTS_AVC)
 191                 return;
 192
 193         spin_lock_irqsave(&transactions_lock, flags);
 194         list_for_each_entry(t, &transactions, list) {
 195                 struct fw_device *device = fw_parent_device(t->unit);
 196                 if (device->card != card ||
 197                     device->generation != generation)
 198                         continue;
 199                 smp_rmb(); /* node_id vs. generation */
 200                 if (device->node_id != source)
 201                         continue;
 202
 203                 if (t->state == STATE_PENDING &&
 204                     is_matching_response(t, data, length)) {
 205                         if (t->deferrable && *(const u8 *)data == 0x0f) {
 206                                 t->state = STATE_DEFERRED;
 207                         } else {
 208                                 t->state = STATE_COMPLETE;
 209                                 t->response_size = min_t(unsigned int, length,
 210                                                          t->response_size);
 211                                 memcpy(t->response_buffer, data,
 212                                        t->response_size);
 213                         }
 214                         wake_up(&t->wait);
 215                 }
 216         }
 217         spin_unlock_irqrestore(&transactions_lock, flags);
 218 }
 219
 220 static struct fw_address_handler response_register_handler = {
 221         .length = 0x200,
 222         .address_callback = fcp_response,
 223 };
 224
 225 static int __init fcp_module_init(void)
 226 {
 227         static const struct fw_address_region response_register_region = {
 228                 .start = CSR_REGISTER_BASE + CSR_FCP_RESPONSE,
 229                 .end = CSR_REGISTER_BASE + CSR_FCP_END,
 230         };
 231
 232         fw_core_add_address_handler(&response_register_handler,
 233                                     &response_register_region);
 234
 235         return 0;
 236 }
 237
 238 static void __exit fcp_module_exit(void)
 239 {
 240         WARN_ON(!list_empty(&transactions));
 241         fw_core_remove_address_handler(&response_register_handler);
 242 }
 243
 244 module_init(fcp_module_init);
 245 module_exit(fcp_module_exit);