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