core-device.c

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/*
 * Device probing and sysfs code.
 *
 * Copyright (C) 2005-2006  Kristian Hoegsberg <[email protected]>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 */

#include <linux/bug.h>
#include <linux/ctype.h>
#include <linux/delay.h>
#include <linux/device.h>
#include <linux/errno.h>
#include <linux/firewire.h>
#include <linux/firewire-constants.h>
#include <linux/idr.h>
#include <linux/jiffies.h>
#include <linux/kobject.h>
#include <linux/list.h>
#include <linux/mod_devicetable.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/random.h>
#include <linux/rwsem.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/string.h>
#include <linux/workqueue.h>

#include <linux/atomic.h>
#include <asm/byteorder.h>

#include "core.h"

void fw_csr_iterator_init(struct fw_csr_iterator *ci, const u32 *p)
{
    ci->p = p + 1;
    ci->end = ci->p + (p[0] >> 16);
}
EXPORT_SYMBOL(fw_csr_iterator_init);

int fw_csr_iterator_next(struct fw_csr_iterator *ci, int *key, int *value)
{
    *key = *ci->p >> 24;
    *value = *ci->p & 0xffffff;

    return ci->p++ < ci->end;
}
EXPORT_SYMBOL(fw_csr_iterator_next);

static const u32 *search_leaf(const u32 *directory, int search_key)
{
    struct fw_csr_iterator ci;
    int last_key = 0, key, value;

    fw_csr_iterator_init(&ci, directory);
    while (fw_csr_iterator_next(&ci, &key, &value)) {
        if (last_key == search_key &&
            key == (CSR_DESCRIPTOR | CSR_LEAF))
            return ci.p - 1 + value;

        last_key = key;
    }

    return NULL;
}

static int textual_leaf_to_string(const u32 *block, char *buf, size_t size)
{
    unsigned int quadlets, i;
    char c;

    if (!size || !buf)
        return -EINVAL;

    quadlets = min(block[0] >> 16, 256U);
    if (quadlets < 2)
        return -ENODATA;

    if (block[1] != 0 || block[2] != 0)
        /* unknown language/character set */
        return -ENODATA;

    block += 3;
    quadlets -= 2;
    for (i = 0; i < quadlets * 4 && i < size - 1; i++) {
        c = block[i / 4] >> (24 - 8 * (i % 4));
        if (c == '\0')
            break;
        buf[i] = c;
    }
    buf[i] = '\0';

    return i;
}

int fw_csr_string(const u32 *directory, int key, char *buf, size_t size)
{
    const u32 *leaf = search_leaf(directory, key);
    if (!leaf)
        return -ENOENT;

    return textual_leaf_to_string(leaf, buf, size);
}
EXPORT_SYMBOL(fw_csr_string);

static void get_ids(const u32 *directory, int *id)
{
    struct fw_csr_iterator ci;
    int key, value;

    fw_csr_iterator_init(&ci, directory);
    while (fw_csr_iterator_next(&ci, &key, &value)) {
        switch (key) {
        case CSR_VENDOR:    id[0] = value; break;
        case CSR_MODEL:     id[1] = value; break;
        case CSR_SPECIFIER_ID:  id[2] = value; break;
        case CSR_VERSION:   id[3] = value; break;
        }
    }
}

static void get_modalias_ids(struct fw_unit *unit, int *id)
{
    get_ids(&fw_parent_device(unit)->config_rom[5], id);
    get_ids(unit->directory, id);
}

static bool match_ids(const struct ieee1394_device_id *id_table, int *id)
{
    int match = 0;

    if (id[0] == id_table->vendor_id)
        match |= IEEE1394_MATCH_VENDOR_ID;
    if (id[1] == id_table->model_id)
        match |= IEEE1394_MATCH_MODEL_ID;
    if (id[2] == id_table->specifier_id)
        match |= IEEE1394_MATCH_SPECIFIER_ID;
    if (id[3] == id_table->version)
        match |= IEEE1394_MATCH_VERSION;

    return (match & id_table->match_flags) == id_table->match_flags;
}

static bool is_fw_unit(struct device *dev);

static int fw_unit_match(struct device *dev, struct device_driver *drv)
{
    const struct ieee1394_device_id *id_table =
            container_of(drv, struct fw_driver, driver)->id_table;
    int id[] = {0, 0, 0, 0};

    /* We only allow binding to fw_units. */
    if (!is_fw_unit(dev))
        return 0;

    get_modalias_ids(fw_unit(dev), id);

    for (; id_table->match_flags != 0; id_table++)
        if (match_ids(id_table, id))
            return 1;

    return 0;
}

static int get_modalias(struct fw_unit *unit, char *buffer, size_t buffer_size)
{
    int id[] = {0, 0, 0, 0};

    get_modalias_ids(unit, id);

    return snprintf(buffer, buffer_size,
            "ieee1394:ven%08Xmo%08Xsp%08Xver%08X",
            id[0], id[1], id[2], id[3]);
}

static int fw_unit_uevent(struct device *dev, struct kobj_uevent_env *env)
{
    struct fw_unit *unit = fw_unit(dev);
    char modalias[64];

    get_modalias(unit, modalias, sizeof(modalias));

    if (add_uevent_var(env, "MODALIAS=%s", modalias))
        return -ENOMEM;

    return 0;
}

struct bus_type fw_bus_type = {
    .name = "firewire",
    .match = fw_unit_match,
};
EXPORT_SYMBOL(fw_bus_type);

int fw_device_enable_phys_dma(struct fw_device *device)
{
    int generation = device->generation;

    /* device->node_id, accessed below, must not be older than generation */
    smp_rmb();

    return device->card->driver->enable_phys_dma(device->card,
                             device->node_id,
                             generation);
}
EXPORT_SYMBOL(fw_device_enable_phys_dma);

struct config_rom_attribute {
    struct device_attribute attr;
    u32 key;
};

static ssize_t show_immediate(struct device *dev,
                  struct device_attribute *dattr, char *buf)
{
    struct config_rom_attribute *attr =
        container_of(dattr, struct config_rom_attribute, attr);
    struct fw_csr_iterator ci;
    const u32 *dir;
    int key, value, ret = -ENOENT;

    down_read(&fw_device_rwsem);

    if (is_fw_unit(dev))
        dir = fw_unit(dev)->directory;
    else
        dir = fw_device(dev)->config_rom + 5;

    fw_csr_iterator_init(&ci, dir);
    while (fw_csr_iterator_next(&ci, &key, &value))
        if (attr->key == key) {
            ret = snprintf(buf, buf ? PAGE_SIZE : 0,
                       "0x%06x\n", value);
            break;
        }

    up_read(&fw_device_rwsem);

    return ret;
}

#define IMMEDIATE_ATTR(name, key)               \
    { __ATTR(name, S_IRUGO, show_immediate, NULL), key }

static ssize_t show_text_leaf(struct device *dev,
                  struct device_attribute *dattr, char *buf)
{
    struct config_rom_attribute *attr =
        container_of(dattr, struct config_rom_attribute, attr);
    const u32 *dir;
    size_t bufsize;
    char dummy_buf[2];
    int ret;

    down_read(&fw_device_rwsem);

    if (is_fw_unit(dev))
        dir = fw_unit(dev)->directory;
    else
        dir = fw_device(dev)->config_rom + 5;

    if (buf) {
        bufsize = PAGE_SIZE - 1;
    } else {
        buf = dummy_buf;
        bufsize = 1;
    }

    ret = fw_csr_string(dir, attr->key, buf, bufsize);

    if (ret >= 0) {
        /* Strip trailing whitespace and add newline. */
        while (ret > 0 && isspace(buf[ret - 1]))
            ret--;
        strcpy(buf + ret, "\n");
        ret++;
    }

    up_read(&fw_device_rwsem);

    return ret;
}

#define TEXT_LEAF_ATTR(name, key)               \
    { __ATTR(name, S_IRUGO, show_text_leaf, NULL), key }

static struct config_rom_attribute config_rom_attributes[] = {
    IMMEDIATE_ATTR(vendor, CSR_VENDOR),
    IMMEDIATE_ATTR(hardware_version, CSR_HARDWARE_VERSION),
    IMMEDIATE_ATTR(specifier_id, CSR_SPECIFIER_ID),
    IMMEDIATE_ATTR(version, CSR_VERSION),
    IMMEDIATE_ATTR(model, CSR_MODEL),
    TEXT_LEAF_ATTR(vendor_name, CSR_VENDOR),
    TEXT_LEAF_ATTR(model_name, CSR_MODEL),
    TEXT_LEAF_ATTR(hardware_version_name, CSR_HARDWARE_VERSION),
};

static void init_fw_attribute_group(struct device *dev,
                    struct device_attribute *attrs,
                    struct fw_attribute_group *group)
{
    struct device_attribute *attr;
    int i, j;

    for (j = 0; attrs[j].attr.name != NULL; j++)
        group->attrs[j] = &attrs[j].attr;

    for (i = 0; i < ARRAY_SIZE(config_rom_attributes); i++) {
        attr = &config_rom_attributes[i].attr;
        if (attr->show(dev, attr, NULL) < 0)
            continue;
        group->attrs[j++] = &attr->attr;
    }

    group->attrs[j] = NULL;
    group->groups[0] = &group->group;
    group->groups[1] = NULL;
    group->group.attrs = group->attrs;
    dev->groups = (const struct attribute_group **) group->groups;
}

static ssize_t modalias_show(struct device *dev,
                 struct device_attribute *attr, char *buf)
{
    struct fw_unit *unit = fw_unit(dev);
    int length;

    length = get_modalias(unit, buf, PAGE_SIZE);
    strcpy(buf + length, "\n");

    return length + 1;
}

static ssize_t rom_index_show(struct device *dev,
                  struct device_attribute *attr, char *buf)
{
    struct fw_device *device = fw_device(dev->parent);
    struct fw_unit *unit = fw_unit(dev);

    return snprintf(buf, PAGE_SIZE, "%d\n",
            (int)(unit->directory - device->config_rom));
}

static struct device_attribute fw_unit_attributes[] = {
    __ATTR_RO(modalias),
    __ATTR_RO(rom_index),
    __ATTR_NULL,
};

static ssize_t config_rom_show(struct device *dev,
                   struct device_attribute *attr, char *buf)
{
    struct fw_device *device = fw_device(dev);
    size_t length;

    down_read(&fw_device_rwsem);
    length = device->config_rom_length * 4;
    memcpy(buf, device->config_rom, length);
    up_read(&fw_device_rwsem);

    return length;
}

static ssize_t guid_show(struct device *dev,
             struct device_attribute *attr, char *buf)
{
    struct fw_device *device = fw_device(dev);
    int ret;

    down_read(&fw_device_rwsem);
    ret = snprintf(buf, PAGE_SIZE, "0x%08x%08x\n",
               device->config_rom[3], device->config_rom[4]);
    up_read(&fw_device_rwsem);

    return ret;
}

static ssize_t is_local_show(struct device *dev,
                 struct device_attribute *attr, char *buf)
{
    struct fw_device *device = fw_device(dev);

    return sprintf(buf, "%u\n", device->is_local);
}

static int units_sprintf(char *buf, const u32 *directory)
{
    struct fw_csr_iterator ci;
    int key, value;
    int specifier_id = 0;
    int version = 0;

    fw_csr_iterator_init(&ci, directory);
    while (fw_csr_iterator_next(&ci, &key, &value)) {
        switch (key) {
        case CSR_SPECIFIER_ID:
            specifier_id = value;
            break;
        case CSR_VERSION:
            version = value;
            break;
        }
    }

    return sprintf(buf, "0x%06x:0x%06x ", specifier_id, version);
}

static ssize_t units_show(struct device *dev,
              struct device_attribute *attr, char *buf)
{
    struct fw_device *device = fw_device(dev);
    struct fw_csr_iterator ci;
    int key, value, i = 0;

    down_read(&fw_device_rwsem);
    fw_csr_iterator_init(&ci, &device->config_rom[5]);
    while (fw_csr_iterator_next(&ci, &key, &value)) {
        if (key != (CSR_UNIT | CSR_DIRECTORY))
            continue;
        i += units_sprintf(&buf[i], ci.p + value - 1);
        if (i >= PAGE_SIZE - (8 + 1 + 8 + 1))
            break;
    }
    up_read(&fw_device_rwsem);

    if (i)
        buf[i - 1] = '\n';

    return i;
}

static struct device_attribute fw_device_attributes[] = {
    __ATTR_RO(config_rom),
    __ATTR_RO(guid),
    __ATTR_RO(is_local),
    __ATTR_RO(units),
    __ATTR_NULL,
};

static int read_rom(struct fw_device *device,
            int generation, int index, u32 *data)
{
    u64 offset = (CSR_REGISTER_BASE | CSR_CONFIG_ROM) + index * 4;
    int i, rcode;

    /* device->node_id, accessed below, must not be older than generation */
    smp_rmb();

    for (i = 10; i < 100; i += 10) {
        rcode = fw_run_transaction(device->card,
                TCODE_READ_QUADLET_REQUEST, device->node_id,
                generation, device->max_speed, offset, data, 4);
        if (rcode != RCODE_BUSY)
            break;
        msleep(i);
    }
    be32_to_cpus(data);

    return rcode;
}

#define MAX_CONFIG_ROM_SIZE 256

/*
 * Read the bus info block, perform a speed probe, and read all of the rest of
 * the config ROM.  We do all this with a cached bus generation.  If the bus
 * generation changes under us, read_config_rom will fail and get retried.
 * It's better to start all over in this case because the node from which we
 * are reading the ROM may have changed the ROM during the reset.
 * Returns either a result code or a negative error code.
 */
static int read_config_rom(struct fw_device *device, int generation)
{
    struct fw_card *card = device->card;
    const u32 *old_rom, *new_rom;
    u32 *rom, *stack;
    u32 sp, key;
    int i, end, length, ret;

    rom = kmalloc(sizeof(*rom) * MAX_CONFIG_ROM_SIZE +
              sizeof(*stack) * MAX_CONFIG_ROM_SIZE, GFP_KERNEL);
    if (rom == NULL)
        return -ENOMEM;

    stack = &rom[MAX_CONFIG_ROM_SIZE];
    memset(rom, 0, sizeof(*rom) * MAX_CONFIG_ROM_SIZE);

    device->max_speed = SCODE_100;

    /* First read the bus info block. */
    for (i = 0; i < 5; i++) {
        ret = read_rom(device, generation, i, &rom[i]);
        if (ret != RCODE_COMPLETE)
            goto out;
        /*
         * As per IEEE1212 7.2, during initialization, devices can
         * reply with a 0 for the first quadlet of the config
         * rom to indicate that they are booting (for example,
         * if the firmware is on the disk of a external
         * harddisk).  In that case we just fail, and the
         * retry mechanism will try again later.
         */
        if (i == 0 && rom[i] == 0) {
            ret = RCODE_BUSY;
            goto out;
        }
    }

    device->max_speed = device->node->max_speed;

    /*
     * Determine the speed of
     *   - devices with link speed less than PHY speed,
     *   - devices with 1394b PHY (unless only connected to 1394a PHYs),
     *   - all devices if there are 1394b repeaters.
     * Note, we cannot use the bus info block's link_spd as starting point
     * because some buggy firmwares set it lower than necessary and because
     * 1394-1995 nodes do not have the field.
     */
    if ((rom[2] & 0x7) < device->max_speed ||
        device->max_speed == SCODE_BETA ||
        card->beta_repeaters_present) {
        u32 dummy;

        /* for S1600 and S3200 */
        if (device->max_speed == SCODE_BETA)
            device->max_speed = card->link_speed;

        while (device->max_speed > SCODE_100) {
            if (read_rom(device, generation, 0, &dummy) ==
                RCODE_COMPLETE)
                break;
            device->max_speed--;
        }
    }

    /*
     * Now parse the config rom.  The config rom is a recursive
     * directory structure so we parse it using a stack of
     * references to the blocks that make up the structure.  We
     * push a reference to the root directory on the stack to
     * start things off.
     */
    length = i;
    sp = 0;
    stack[sp++] = 0xc0000005;
    while (sp > 0) {
        /*
         * Pop the next block reference of the stack.  The
         * lower 24 bits is the offset into the config rom,
         * the upper 8 bits are the type of the reference the
         * block.
         */
        key = stack[--sp];
        i = key & 0xffffff;
        if (WARN_ON(i >= MAX_CONFIG_ROM_SIZE)) {
            ret = -ENXIO;
            goto out;
        }

        /* Read header quadlet for the block to get the length. */
        ret = read_rom(device, generation, i, &rom[i]);
        if (ret != RCODE_COMPLETE)
            goto out;
        end = i + (rom[i] >> 16) + 1;
        if (end > MAX_CONFIG_ROM_SIZE) {
            /*
             * This block extends outside the config ROM which is
             * a firmware bug.  Ignore this whole block, i.e.
             * simply set a fake block length of 0.
             */
            fw_err(card, "skipped invalid ROM block %x at %llx\n",
                   rom[i],
                   i * 4 | CSR_REGISTER_BASE | CSR_CONFIG_ROM);
            rom[i] = 0;
            end = i;
        }
        i++;

        /*
         * Now read in the block.  If this is a directory
         * block, check the entries as we read them to see if
         * it references another block, and push it in that case.
         */
        for (; i < end; i++) {
            ret = read_rom(device, generation, i, &rom[i]);
            if (ret != RCODE_COMPLETE)
                goto out;

            if ((key >> 30) != 3 || (rom[i] >> 30) < 2)
                continue;
            /*
             * Offset points outside the ROM.  May be a firmware
             * bug or an Extended ROM entry (IEEE 1212-2001 clause
             * 7.7.18).  Simply overwrite this pointer here by a
             * fake immediate entry so that later iterators over
             * the ROM don't have to check offsets all the time.
             */
            if (i + (rom[i] & 0xffffff) >= MAX_CONFIG_ROM_SIZE) {
                fw_err(card,
                       "skipped unsupported ROM entry %x at %llx\n",
                       rom[i],
                       i * 4 | CSR_REGISTER_BASE | CSR_CONFIG_ROM);
                rom[i] = 0;
                continue;
            }
            stack[sp++] = i + rom[i];
        }
        if (length < i)
            length = i;
    }

    old_rom = device->config_rom;
    new_rom = kmemdup(rom, length * 4, GFP_KERNEL);
    if (new_rom == NULL) {
        ret = -ENOMEM;
        goto out;
    }

    down_write(&fw_device_rwsem);
    device->config_rom = new_rom;
    device->config_rom_length = length;
    up_write(&fw_device_rwsem);

    kfree(old_rom);
    ret = RCODE_COMPLETE;
    device->max_rec = rom[2] >> 12 & 0xf;
    device->cmc = rom[2] >> 30 & 1;
    device->irmc    = rom[2] >> 31 & 1;
 out:
    kfree(rom);

    return ret;
}

static void fw_unit_release(struct device *dev)
{
    struct fw_unit *unit = fw_unit(dev);

    fw_device_put(fw_parent_device(unit));
    kfree(unit);
}

static struct device_type fw_unit_type = {
    .uevent     = fw_unit_uevent,
    .release    = fw_unit_release,
};

static bool is_fw_unit(struct device *dev)
{
    return dev->type == &fw_unit_type;
}

static void create_units(struct fw_device *device)
{
    struct fw_csr_iterator ci;
    struct fw_unit *unit;
    int key, value, i;

    i = 0;
    fw_csr_iterator_init(&ci, &device->config_rom[5]);
    while (fw_csr_iterator_next(&ci, &key, &value)) {
        if (key != (CSR_UNIT | CSR_DIRECTORY))
            continue;

        /*
         * Get the address of the unit directory and try to
         * match the drivers id_tables against it.
         */
        unit = kzalloc(sizeof(*unit), GFP_KERNEL);
        if (unit == NULL) {
            fw_err(device->card, "out of memory for unit\n");
            continue;
        }

        unit->directory = ci.p + value - 1;
        unit->device.bus = &fw_bus_type;
        unit->device.type = &fw_unit_type;
        unit->device.parent = &device->device;
        dev_set_name(&unit->device, "%s.%d", dev_name(&device->device), i++);

        BUILD_BUG_ON(ARRAY_SIZE(unit->attribute_group.attrs) <
                ARRAY_SIZE(fw_unit_attributes) +
                ARRAY_SIZE(config_rom_attributes));
        init_fw_attribute_group(&unit->device,
                    fw_unit_attributes,
                    &unit->attribute_group);

        if (device_register(&unit->device) < 0)
            goto skip_unit;

        fw_device_get(device);
        continue;

    skip_unit:
        kfree(unit);
    }
}

static int shutdown_unit(struct device *device, void *data)
{
    device_unregister(device);

    return 0;
}

/*
 * fw_device_rwsem acts as dual purpose mutex:
 *   - serializes accesses to fw_device_idr,
 *   - serializes accesses to fw_device.config_rom/.config_rom_length and
 *     fw_unit.directory, unless those accesses happen at safe occasions
 */
DECLARE_RWSEM(fw_device_rwsem);

DEFINE_IDR(fw_device_idr);
int fw_cdev_major;

struct fw_device *fw_device_get_by_devt(dev_t devt)
{
    struct fw_device *device;

    down_read(&fw_device_rwsem);
    device = idr_find(&fw_device_idr, MINOR(devt));
    if (device)
        fw_device_get(device);
    up_read(&fw_device_rwsem);

    return device;
}

struct workqueue_struct *fw_workqueue;
EXPORT_SYMBOL(fw_workqueue);

static void fw_schedule_device_work(struct fw_device *device,
                    unsigned long delay)
{
    queue_delayed_work(fw_workqueue, &device->work, delay);
}

/*
 * These defines control the retry behavior for reading the config
 * rom.  It shouldn't be necessary to tweak these; if the device
 * doesn't respond to a config rom read within 10 seconds, it's not
 * going to respond at all.  As for the initial delay, a lot of
 * devices will be able to respond within half a second after bus
 * reset.  On the other hand, it's not really worth being more
 * aggressive than that, since it scales pretty well; if 10 devices
 * are plugged in, they're all getting read within one second.
 */

#define MAX_RETRIES 10
#define RETRY_DELAY (3 * HZ)
#define INITIAL_DELAY   (HZ / 2)
#define SHUTDOWN_DELAY  (2 * HZ)

static void fw_device_shutdown(struct work_struct *work)
{
    struct fw_device *device =
        container_of(work, struct fw_device, work.work);
    int minor = MINOR(device->device.devt);

    if (time_before64(get_jiffies_64(),
              device->card->reset_jiffies + SHUTDOWN_DELAY)
        && !list_empty(&device->card->link)) {
        fw_schedule_device_work(device, SHUTDOWN_DELAY);
        return;
    }

    if (atomic_cmpxchg(&device->state,
               FW_DEVICE_GONE,
               FW_DEVICE_SHUTDOWN) != FW_DEVICE_GONE)
        return;

    fw_device_cdev_remove(device);
    device_for_each_child(&device->device, NULL, shutdown_unit);
    device_unregister(&device->device);

    down_write(&fw_device_rwsem);
    idr_remove(&fw_device_idr, minor);
    up_write(&fw_device_rwsem);

    fw_device_put(device);
}

static void fw_device_release(struct device *dev)
{
    struct fw_device *device = fw_device(dev);
    struct fw_card *card = device->card;
    unsigned long flags;

    /*
     * Take the card lock so we don't set this to NULL while a
     * FW_NODE_UPDATED callback is being handled or while the
     * bus manager work looks at this node.
     */
    spin_lock_irqsave(&card->lock, flags);
    device->node->data = NULL;
    spin_unlock_irqrestore(&card->lock, flags);

    fw_node_put(device->node);
    kfree(device->config_rom);
    kfree(device);
    fw_card_put(card);
}

static struct device_type fw_device_type = {
    .release = fw_device_release,
};

static bool is_fw_device(struct device *dev)
{
    return dev->type == &fw_device_type;
}

static int update_unit(struct device *dev, void *data)
{
    struct fw_unit *unit = fw_unit(dev);
    struct fw_driver *driver = (struct fw_driver *)dev->driver;

    if (is_fw_unit(dev) && driver != NULL && driver->update != NULL) {
        device_lock(dev);
        driver->update(unit);
        device_unlock(dev);
    }

    return 0;
}

static void fw_device_update(struct work_struct *work)
{
    struct fw_device *device =
        container_of(work, struct fw_device, work.work);

    fw_device_cdev_update(device);
    device_for_each_child(&device->device, NULL, update_unit);
}

/*
 * If a device was pending for deletion because its node went away but its
 * bus info block and root directory header matches that of a newly discovered
 * device, revive the existing fw_device.
 * The newly allocated fw_device becomes obsolete instead.
 */
static int lookup_existing_device(struct device *dev, void *data)
{
    struct fw_device *old = fw_device(dev);
    struct fw_device *new = data;
    struct fw_card *card = new->card;
    int match = 0;

    if (!is_fw_device(dev))
        return 0;

    down_read(&fw_device_rwsem); /* serialize config_rom access */
    spin_lock_irq(&card->lock);  /* serialize node access */

    if (memcmp(old->config_rom, new->config_rom, 6 * 4) == 0 &&
        atomic_cmpxchg(&old->state,
               FW_DEVICE_GONE,
               FW_DEVICE_RUNNING) == FW_DEVICE_GONE) {
        struct fw_node *current_node = new->node;
        struct fw_node *obsolete_node = old->node;

        new->node = obsolete_node;
        new->node->data = new;
        old->node = current_node;
        old->node->data = old;

        old->max_speed = new->max_speed;
        old->node_id = current_node->node_id;
        smp_wmb();  /* update node_id before generation */
        old->generation = card->generation;
        old->config_rom_retries = 0;
        fw_notice(card, "rediscovered device %s\n", dev_name(dev));

        PREPARE_DELAYED_WORK(&old->work, fw_device_update);
        fw_schedule_device_work(old, 0);

        if (current_node == card->root_node)
            fw_schedule_bm_work(card, 0);

        match = 1;
    }

    spin_unlock_irq(&card->lock);
    up_read(&fw_device_rwsem);

    return match;
}

enum { BC_UNKNOWN = 0, BC_UNIMPLEMENTED, BC_IMPLEMENTED, };

static void set_broadcast_channel(struct fw_device *device, int generation)
{
    struct fw_card *card = device->card;
    __be32 data;
    int rcode;

    if (!card->broadcast_channel_allocated)
        return;

    /*
     * The Broadcast_Channel Valid bit is required by nodes which want to
     * transmit on this channel.  Such transmissions are practically
     * exclusive to IP over 1394 (RFC 2734).  IP capable nodes are required
     * to be IRM capable and have a max_rec of 8 or more.  We use this fact
     * to narrow down to which nodes we send Broadcast_Channel updates.
     */
    if (!device->irmc || device->max_rec < 8)
        return;

    /*
     * Some 1394-1995 nodes crash if this 1394a-2000 register is written.
     * Perform a read test first.
     */
    if (device->bc_implemented == BC_UNKNOWN) {
        rcode = fw_run_transaction(card, TCODE_READ_QUADLET_REQUEST,
                device->node_id, generation, device->max_speed,
                CSR_REGISTER_BASE + CSR_BROADCAST_CHANNEL,
                &data, 4);
        switch (rcode) {
        case RCODE_COMPLETE:
            if (data & cpu_to_be32(1 << 31)) {
                device->bc_implemented = BC_IMPLEMENTED;
                break;
            }
            /* else fall through to case address error */
        case RCODE_ADDRESS_ERROR:
            device->bc_implemented = BC_UNIMPLEMENTED;
        }
    }

    if (device->bc_implemented == BC_IMPLEMENTED) {
        data = cpu_to_be32(BROADCAST_CHANNEL_INITIAL |
                   BROADCAST_CHANNEL_VALID);
        fw_run_transaction(card, TCODE_WRITE_QUADLET_REQUEST,
                device->node_id, generation, device->max_speed,
                CSR_REGISTER_BASE + CSR_BROADCAST_CHANNEL,
                &data, 4);
    }
}

int fw_device_set_broadcast_channel(struct device *dev, void *gen)
{
    if (is_fw_device(dev))
        set_broadcast_channel(fw_device(dev), (long)gen);

    return 0;
}

static void fw_device_init(struct work_struct *work)
{
    struct fw_device *device =
        container_of(work, struct fw_device, work.work);
    struct fw_card *card = device->card;
    struct device *revived_dev;
    int minor, ret;

    /*
     * All failure paths here set node->data to NULL, so that we
     * don't try to do device_for_each_child() on a kfree()'d
     * device.
     */

    ret = read_config_rom(device, device->generation);
    if (ret != RCODE_COMPLETE) {
        if (device->config_rom_retries < MAX_RETRIES &&
            atomic_read(&device->state) == FW_DEVICE_INITIALIZING) {
            device->config_rom_retries++;
            fw_schedule_device_work(device, RETRY_DELAY);
        } else {
            if (device->node->link_on)
                fw_notice(card, "giving up on node %x: reading config rom failed: %s\n",
                      device->node_id,
                      fw_rcode_string(ret));
            if (device->node == card->root_node)
                fw_schedule_bm_work(card, 0);
            fw_device_release(&device->device);
        }
        return;
    }

    revived_dev = device_find_child(card->device,
                    device, lookup_existing_device);
    if (revived_dev) {
        put_device(revived_dev);
        fw_device_release(&device->device);

        return;
    }

    device_initialize(&device->device);

    fw_device_get(device);
    down_write(&fw_device_rwsem);
    ret = idr_pre_get(&fw_device_idr, GFP_KERNEL) ?
          idr_get_new(&fw_device_idr, device, &minor) :
          -ENOMEM;
    up_write(&fw_device_rwsem);

    if (ret < 0)
        goto error;

    device->device.bus = &fw_bus_type;
    device->device.type = &fw_device_type;
    device->device.parent = card->device;
    device->device.devt = MKDEV(fw_cdev_major, minor);
    dev_set_name(&device->device, "fw%d", minor);

    BUILD_BUG_ON(ARRAY_SIZE(device->attribute_group.attrs) <
            ARRAY_SIZE(fw_device_attributes) +
            ARRAY_SIZE(config_rom_attributes));
    init_fw_attribute_group(&device->device,
                fw_device_attributes,
                &device->attribute_group);

    if (device_add(&device->device)) {
        fw_err(card, "failed to add device\n");
        goto error_with_cdev;
    }

    create_units(device);

    /*
     * Transition the device to running state.  If it got pulled
     * out from under us while we did the intialization work, we
     * have to shut down the device again here.  Normally, though,
     * fw_node_event will be responsible for shutting it down when
     * necessary.  We have to use the atomic cmpxchg here to avoid
     * racing with the FW_NODE_DESTROYED case in
     * fw_node_event().
     */
    if (atomic_cmpxchg(&device->state,
               FW_DEVICE_INITIALIZING,
               FW_DEVICE_RUNNING) == FW_DEVICE_GONE) {
        PREPARE_DELAYED_WORK(&device->work, fw_device_shutdown);
        fw_schedule_device_work(device, SHUTDOWN_DELAY);
    } else {
        fw_notice(card, "created device %s: GUID %08x%08x, S%d00\n",
              dev_name(&device->device),
              device->config_rom[3], device->config_rom[4],
              1 << device->max_speed);
        device->config_rom_retries = 0;

        set_broadcast_channel(device, device->generation);

        add_device_randomness(&device->config_rom[3], 8);
    }

    /*
     * Reschedule the IRM work if we just finished reading the
     * root node config rom.  If this races with a bus reset we
     * just end up running the IRM work a couple of extra times -
     * pretty harmless.
     */
    if (device->node == card->root_node)
        fw_schedule_bm_work(card, 0);

    return;

 error_with_cdev:
    down_write(&fw_device_rwsem);
    idr_remove(&fw_device_idr, minor);
    up_write(&fw_device_rwsem);
 error:
    fw_device_put(device);      /* fw_device_idr's reference */

    put_device(&device->device);    /* our reference */
}

/* Reread and compare bus info block and header of root directory */
static int reread_config_rom(struct fw_device *device, int generation,
                 bool *changed)
{
    u32 q;
    int i, rcode;

    for (i = 0; i < 6; i++) {
        rcode = read_rom(device, generation, i, &q);
        if (rcode != RCODE_COMPLETE)
            return rcode;

        if (i == 0 && q == 0)
            /* inaccessible (see read_config_rom); retry later */
            return RCODE_BUSY;

        if (q != device->config_rom[i]) {
            *changed = true;
            return RCODE_COMPLETE;
        }
    }

    *changed = false;
    return RCODE_COMPLETE;
}

static void fw_device_refresh(struct work_struct *work)
{
    struct fw_device *device =
        container_of(work, struct fw_device, work.work);
    struct fw_card *card = device->card;
    int ret, node_id = device->node_id;
    bool changed;

    ret = reread_config_rom(device, device->generation, &changed);
    if (ret != RCODE_COMPLETE)
        goto failed_config_rom;

    if (!changed) {
        if (atomic_cmpxchg(&device->state,
                   FW_DEVICE_INITIALIZING,
                   FW_DEVICE_RUNNING) == FW_DEVICE_GONE)
            goto gone;

        fw_device_update(work);
        device->config_rom_retries = 0;
        goto out;
    }

    /*
     * Something changed.  We keep things simple and don't investigate
     * further.  We just destroy all previous units and create new ones.
     */
    device_for_each_child(&device->device, NULL, shutdown_unit);

    ret = read_config_rom(device, device->generation);
    if (ret != RCODE_COMPLETE)
        goto failed_config_rom;

    fw_device_cdev_update(device);
    create_units(device);

    /* Userspace may want to re-read attributes. */
    kobject_uevent(&device->device.kobj, KOBJ_CHANGE);

    if (atomic_cmpxchg(&device->state,
               FW_DEVICE_INITIALIZING,
               FW_DEVICE_RUNNING) == FW_DEVICE_GONE)
        goto gone;

    fw_notice(card, "refreshed device %s\n", dev_name(&device->device));
    device->config_rom_retries = 0;
    goto out;

 failed_config_rom:
    if (device->config_rom_retries < MAX_RETRIES &&
        atomic_read(&device->state) == FW_DEVICE_INITIALIZING) {
        device->config_rom_retries++;
        fw_schedule_device_work(device, RETRY_DELAY);
        return;
    }

    fw_notice(card, "giving up on refresh of device %s: %s\n",
          dev_name(&device->device), fw_rcode_string(ret));
 gone:
    atomic_set(&device->state, FW_DEVICE_GONE);
    PREPARE_DELAYED_WORK(&device->work, fw_device_shutdown);
    fw_schedule_device_work(device, SHUTDOWN_DELAY);
 out:
    if (node_id == card->root_node->node_id)
        fw_schedule_bm_work(card, 0);
}

void fw_node_event(struct fw_card *card, struct fw_node *node, int event)
{
    struct fw_device *device;

    switch (event) {
    case FW_NODE_CREATED:
        /*
         * Attempt to scan the node, regardless whether its self ID has
         * the L (link active) flag set or not.  Some broken devices
         * send L=0 but have an up-and-running link; others send L=1
         * without actually having a link.
         */
 create:
        device = kzalloc(sizeof(*device), GFP_ATOMIC);
        if (device == NULL)
            break;

        /*
         * Do minimal intialization of the device here, the
         * rest will happen in fw_device_init().
         *
         * Attention:  A lot of things, even fw_device_get(),
         * cannot be done before fw_device_init() finished!
         * You can basically just check device->state and
         * schedule work until then, but only while holding
         * card->lock.
         */
        atomic_set(&device->state, FW_DEVICE_INITIALIZING);
        device->card = fw_card_get(card);
        device->node = fw_node_get(node);
        device->node_id = node->node_id;
        device->generation = card->generation;
        device->is_local = node == card->local_node;
        mutex_init(&device->client_list_mutex);
        INIT_LIST_HEAD(&device->client_list);

        /*
         * Set the node data to point back to this device so
         * FW_NODE_UPDATED callbacks can update the node_id
         * and generation for the device.
         */
        node->data = device;

        /*
         * Many devices are slow to respond after bus resets,
         * especially if they are bus powered and go through
         * power-up after getting plugged in.  We schedule the
         * first config rom scan half a second after bus reset.
         */
        INIT_DELAYED_WORK(&device->work, fw_device_init);
        fw_schedule_device_work(device, INITIAL_DELAY);
        break;

    case FW_NODE_INITIATED_RESET:
    case FW_NODE_LINK_ON:
        device = node->data;
        if (device == NULL)
            goto create;

        device->node_id = node->node_id;
        smp_wmb();  /* update node_id before generation */
        device->generation = card->generation;
        if (atomic_cmpxchg(&device->state,
                FW_DEVICE_RUNNING,
                FW_DEVICE_INITIALIZING) == FW_DEVICE_RUNNING) {
            PREPARE_DELAYED_WORK(&device->work, fw_device_refresh);
            fw_schedule_device_work(device,
                device->is_local ? 0 : INITIAL_DELAY);
        }
        break;

    case FW_NODE_UPDATED:
        device = node->data;
        if (device == NULL)
            break;

        device->node_id = node->node_id;
        smp_wmb();  /* update node_id before generation */
        device->generation = card->generation;
        if (atomic_read(&device->state) == FW_DEVICE_RUNNING) {
            PREPARE_DELAYED_WORK(&device->work, fw_device_update);
            fw_schedule_device_work(device, 0);
        }
        break;

    case FW_NODE_DESTROYED:
    case FW_NODE_LINK_OFF:
        if (!node->data)
            break;

        /*
         * Destroy the device associated with the node.  There
         * are two cases here: either the device is fully
         * initialized (FW_DEVICE_RUNNING) or we're in the
         * process of reading its config rom
         * (FW_DEVICE_INITIALIZING).  If it is fully
         * initialized we can reuse device->work to schedule a
         * full fw_device_shutdown().  If not, there's work
         * scheduled to read it's config rom, and we just put
         * the device in shutdown state to have that code fail
         * to create the device.
         */
        device = node->data;
        if (atomic_xchg(&device->state,
                FW_DEVICE_GONE) == FW_DEVICE_RUNNING) {
            PREPARE_DELAYED_WORK(&device->work, fw_device_shutdown);
            fw_schedule_device_work(device,
                list_empty(&card->link) ? 0 : SHUTDOWN_DELAY);
        }
        break;
    }
}