linux/sound/firewire/fcp.c
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   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
  26static DEFINE_SPINLOCK(transactions_lock);
  27static LIST_HEAD(transactions);
  28
  29enum fcp_state {
  30        STATE_PENDING,
  31        STATE_BUS_RESET,
  32        STATE_COMPLETE,
  33};
  34
  35struct 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 */
  69int 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}
 118EXPORT_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 */
 128void 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}
 142EXPORT_SYMBOL(fcp_bus_reset);
 143
 144/* checks whether the response matches the masked bytes in response_buffer */
 145static 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
 166static 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
 199static struct fw_address_handler response_register_handler = {
 200        .length = 0x200,
 201        .address_callback = fcp_response,
 202};
 203
 204static 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
 217static void __exit fcp_module_exit(void)
 218{
 219        WARN_ON(!list_empty(&transactions));
 220        fw_core_remove_address_handler(&response_register_handler);
 221}
 222
 223module_init(fcp_module_init);
 224module_exit(fcp_module_exit);
 225
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