fcp.c

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/*
 * Function Control Protocol (IEC 61883-1) helper functions
 *
 * Copyright (c) Clemens Ladisch <[email protected]>
 * Licensed under the terms of the GNU General Public License, version 2.
 */

#include <linux/device.h>
#include <linux/firewire.h>
#include <linux/firewire-constants.h>
#include <linux/list.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/spinlock.h>
#include <linux/wait.h>
#include <linux/delay.h>
#include "fcp.h"
#include "lib.h"

#define CTS_AVC 0x00

#define ERROR_RETRIES   3
#define ERROR_DELAY_MS  5
#define FCP_TIMEOUT_MS  125

static DEFINE_SPINLOCK(transactions_lock);
static LIST_HEAD(transactions);

enum fcp_state {
    STATE_PENDING,
    STATE_BUS_RESET,
    STATE_COMPLETE,
};

struct fcp_transaction {
    struct list_head list;
    struct fw_unit *unit;
    void *response_buffer;
    unsigned int response_size;
    unsigned int response_match_bytes;
    enum fcp_state state;
    wait_queue_head_t wait;
};

int fcp_avc_transaction(struct fw_unit *unit,
            const void *command, unsigned int command_size,
            void *response, unsigned int response_size,
            unsigned int response_match_bytes)
{
    struct fcp_transaction t;
    int tcode, ret, tries = 0;

    t.unit = unit;
    t.response_buffer = response;
    t.response_size = response_size;
    t.response_match_bytes = response_match_bytes;
    t.state = STATE_PENDING;
    init_waitqueue_head(&t.wait);

    spin_lock_irq(&transactions_lock);
    list_add_tail(&t.list, &transactions);
    spin_unlock_irq(&transactions_lock);

    for (;;) {
        tcode = command_size == 4 ? TCODE_WRITE_QUADLET_REQUEST
                      : TCODE_WRITE_BLOCK_REQUEST;
        ret = snd_fw_transaction(t.unit, tcode,
                     CSR_REGISTER_BASE + CSR_FCP_COMMAND,
                     (void *)command, command_size);
        if (ret < 0)
            break;

        wait_event_timeout(t.wait, t.state != STATE_PENDING,
                   msecs_to_jiffies(FCP_TIMEOUT_MS));

        if (t.state == STATE_COMPLETE) {
            ret = t.response_size;
            break;
        } else if (t.state == STATE_BUS_RESET) {
            msleep(ERROR_DELAY_MS);
        } else if (++tries >= ERROR_RETRIES) {
            dev_err(&t.unit->device, "FCP command timed out\n");
            ret = -EIO;
            break;
        }
    }

    spin_lock_irq(&transactions_lock);
    list_del(&t.list);
    spin_unlock_irq(&transactions_lock);

    return ret;
}
EXPORT_SYMBOL(fcp_avc_transaction);

void fcp_bus_reset(struct fw_unit *unit)
{
    struct fcp_transaction *t;

    spin_lock_irq(&transactions_lock);
    list_for_each_entry(t, &transactions, list) {
        if (t->unit == unit &&
            t->state == STATE_PENDING) {
            t->state = STATE_BUS_RESET;
            wake_up(&t->wait);
        }
    }
    spin_unlock_irq(&transactions_lock);
}
EXPORT_SYMBOL(fcp_bus_reset);

/* checks whether the response matches the masked bytes in response_buffer */
static bool is_matching_response(struct fcp_transaction *transaction,
                 const void *response, size_t length)
{
    const u8 *p1, *p2;
    unsigned int mask, i;

    p1 = response;
    p2 = transaction->response_buffer;
    mask = transaction->response_match_bytes;

    for (i = 0; ; ++i) {
        if ((mask & 1) && p1[i] != p2[i])
            return false;
        mask >>= 1;
        if (!mask)
            return true;
        if (--length == 0)
            return false;
    }
}

static void fcp_response(struct fw_card *card, struct fw_request *request,
             int tcode, int destination, int source,
             int generation, unsigned long long offset,
             void *data, size_t length, void *callback_data)
{
    struct fcp_transaction *t;
    unsigned long flags;

    if (length < 1 || (*(const u8 *)data & 0xf0) != CTS_AVC)
        return;

    spin_lock_irqsave(&transactions_lock, flags);
    list_for_each_entry(t, &transactions, list) {
        struct fw_device *device = fw_parent_device(t->unit);
        if (device->card != card ||
            device->generation != generation)
            continue;
        smp_rmb(); /* node_id vs. generation */
        if (device->node_id != source)
            continue;

        if (t->state == STATE_PENDING &&
            is_matching_response(t, data, length)) {
            t->state = STATE_COMPLETE;
            t->response_size = min((unsigned int)length,
                           t->response_size);
            memcpy(t->response_buffer, data, t->response_size);
            wake_up(&t->wait);
        }
    }
    spin_unlock_irqrestore(&transactions_lock, flags);
}

static struct fw_address_handler response_register_handler = {
    .length = 0x200,
    .address_callback = fcp_response,
};

static int __init fcp_module_init(void)
{
    static const struct fw_address_region response_register_region = {
        .start = CSR_REGISTER_BASE + CSR_FCP_RESPONSE,
        .end = CSR_REGISTER_BASE + CSR_FCP_END,
    };

    fw_core_add_address_handler(&response_register_handler,
                    &response_register_region);

    return 0;
}

static void __exit fcp_module_exit(void)
{
    WARN_ON(!list_empty(&transactions));
    fw_core_remove_address_handler(&response_register_handler);
}

module_init(fcp_module_init);
module_exit(fcp_module_exit);