// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Device probing and sysfs code.
 *
 * Copyright (C) 2005-2006  Kristian Hoegsberg <krh@bitplanet.net>
 */

#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/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"

#define ROOT_DIR_OFFSET 5

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_directory(const u32 *directory, int search_key)
{
        struct fw_csr_iterator ci;
        int key, value;

        search_key |= CSR_DIRECTORY;

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

        return NULL;
}

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;
}

/**
 * fw_csr_string() - reads a string from the configuration ROM
 * @directory:  e.g. root directory or unit directory
 * @key:        the key of the preceding directory entry
 * @buf:        where to put the string
 * @size:       size of @buf, in bytes
 *
 * The string is taken from a minimal ASCII text descriptor leaf just after the entry with the
 * @key. The string is zero-terminated. An overlong string is silently truncated such that it
 * and the zero byte fit into @size.
 *
 * Returns strlen(buf) or a negative error code.
 */
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(const struct fw_unit *unit, int *id)
{
        const u32 *root_directory = &fw_parent_device(unit)->config_rom[ROOT_DIR_OFFSET];
        const u32 *directories[] = {NULL, NULL, NULL};
        const u32 *vendor_directory;
        int i;

        directories[0] = root_directory;

        // Legacy layout of configuration ROM described in Annex 1 of 'Configuration ROM for AV/C
        // Devices 1.0 (December 12, 2000, 1394 Trading Association, TA Document 1999027)'.
        vendor_directory = search_directory(root_directory, CSR_VENDOR);
        if (!vendor_directory) {
                directories[1] = unit->directory;
        } else {
                directories[1] = vendor_directory;
                directories[2] = unit->directory;
        }

        for (i = 0; i < ARRAY_SIZE(directories) && !!directories[i]; ++i)
                get_ids(directories[i], 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 const struct ieee1394_device_id *unit_match(struct device *dev,
                                                   const struct device_driver *drv)
{
        const struct ieee1394_device_id *id_table =
                        container_of_const(drv, struct fw_driver, driver)->id_table;
        int id[] = {0, 0, 0, 0};

        get_modalias_ids(fw_unit(dev), id);

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

        return NULL;
}

static bool is_fw_unit(const struct device *dev);

static int fw_unit_match(struct device *dev, const struct device_driver *drv)
{
        /* We only allow binding to fw_units. */
        return is_fw_unit(dev) && unit_match(dev, drv) != NULL;
}

static int fw_unit_probe(struct device *dev)
{
        struct fw_driver *driver =
                        container_of(dev->driver, struct fw_driver, driver);

        return driver->probe(fw_unit(dev), unit_match(dev, dev->driver));
}

static void fw_unit_remove(struct device *dev)
{
        struct fw_driver *driver =
                        container_of(dev->driver, struct fw_driver, driver);

        driver->remove(fw_unit(dev));
}

static int get_modalias(const 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(const struct device *dev, struct kobj_uevent_env *env)
{
        const 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;
}

const struct bus_type fw_bus_type = {
        .name = "firewire",
        .match = fw_unit_match,
        .probe = fw_unit_probe,
        .remove = fw_unit_remove,
};
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 *directories[] = {NULL, NULL};
        int i, value = -1;

        guard(rwsem_read)(&fw_device_rwsem);

        if (is_fw_unit(dev)) {
                directories[0] = fw_unit(dev)->directory;
        } else {
                const u32 *root_directory = fw_device(dev)->config_rom + ROOT_DIR_OFFSET;
                const u32 *vendor_directory = search_directory(root_directory, CSR_VENDOR);

                if (!vendor_directory) {
                        directories[0] = root_directory;
                } else {
                        // Legacy layout of configuration ROM described in Annex 1 of
                        // 'Configuration ROM for AV/C Devices 1.0 (December 12, 2000, 1394 Trading
                        // Association, TA Document 1999027)'.
                        directories[0] = vendor_directory;
                        directories[1] = root_directory;
                }
        }

        for (i = 0; i < ARRAY_SIZE(directories) && !!directories[i]; ++i) {
                int key, val;

                fw_csr_iterator_init(&ci, directories[i]);
                while (fw_csr_iterator_next(&ci, &key, &val)) {
                        if (attr->key == key)
                                value = val;
                }
        }

        if (value < 0)
                return -ENOENT;

        // Note that this function is also called by init_fw_attribute_group() with NULL pointer.
        return buf ? sysfs_emit(buf, "0x%06x\n", value) : 0;
}

#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 *directories[] = {NULL, NULL};
        size_t bufsize;
        char dummy_buf[2];
        int i, ret = -ENOENT;

        guard(rwsem_read)(&fw_device_rwsem);

        if (is_fw_unit(dev)) {
                directories[0] = fw_unit(dev)->directory;
        } else {
                const u32 *root_directory = fw_device(dev)->config_rom + ROOT_DIR_OFFSET;
                const u32 *vendor_directory = search_directory(root_directory, CSR_VENDOR);

                if (!vendor_directory) {
                        directories[0] = root_directory;
                } else {
                        // Legacy layout of configuration ROM described in Annex 1 of
                        // 'Configuration ROM for AV/C Devices 1.0 (December 12, 2000, 1394
                        // Trading Association, TA Document 1999027)'.
                        directories[0] = root_directory;
                        directories[1] = vendor_directory;
                }
        }

        // Note that this function is also called by init_fw_attribute_group() with NULL pointer.
        if (buf) {
                bufsize = PAGE_SIZE - 1;
        } else {
                buf = dummy_buf;
                bufsize = 1;
        }

        for (i = 0; i < ARRAY_SIZE(directories) && !!directories[i]; ++i) {
                int result = fw_csr_string(directories[i], attr->key, buf, bufsize);
                // Detected.
                if (result >= 0) {
                        ret = result;
                } else if (i == 0 && attr->key == CSR_VENDOR) {
                        // Sony DVMC-DA1 has configuration ROM such that the descriptor leaf entry
                        // in the root directory follows to the directory entry for vendor ID
                        // instead of the immediate value for vendor ID.
                        result = fw_csr_string(directories[i], CSR_DIRECTORY | attr->key, buf,
                                               bufsize);
                        if (result >= 0)
                                ret = result;
                }
        }

        if (ret < 0)
                return ret;

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

        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 sysfs_emit(buf, "%td\n", 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;

        guard(rwsem_read)(&fw_device_rwsem);

        length = device->config_rom_length * 4;
        memcpy(buf, device->config_rom, length);

        return length;
}

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

        guard(rwsem_read)(&fw_device_rwsem);

        return sysfs_emit(buf, "0x%08x%08x\n", device->config_rom[3], device->config_rom[4]);
}

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

        return sysfs_emit(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;

        guard(rwsem_read)(&fw_device_rwsem);

        fw_csr_iterator_init(&ci, &device->config_rom[ROOT_DIR_OFFSET]);
        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;
        }

        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,
};

#define CANON_OUI               0x000085

static int detect_quirks_by_bus_information_block(const u32 *bus_information_block)
{
        int quirks = 0;

        if ((bus_information_block[2] & 0x000000f0) == 0)
                quirks |= FW_DEVICE_QUIRK_IRM_IS_1394_1995_ONLY;

        if ((bus_information_block[3] >> 8) == CANON_OUI)
                quirks |= FW_DEVICE_QUIRK_IRM_IGNORES_BUS_MANAGER;

        return quirks;
}

struct entry_match {
        unsigned int index;
        u32 value;
};

static const struct entry_match motu_audio_express_matches[] = {
        { 1, 0x030001f2 },
        { 3, 0xd1000002 },
        { 4, 0x8d000005 },
        { 6, 0x120001f2 },
        { 7, 0x13000033 },
        { 8, 0x17104800 },
};

static const struct entry_match tascam_fw_series_matches[] = {
        { 1, 0x0300022e },
        { 3, 0x8d000006 },
        { 4, 0xd1000001 },
        { 6, 0x1200022e },
        { 8, 0xd4000004 },
};

static int detect_quirks_by_root_directory(const u32 *root_directory, unsigned int length)
{
        static const struct {
                enum fw_device_quirk quirk;
                const struct entry_match *matches;
                unsigned int match_count;
        } *entry, entries[] = {
                {
                        .quirk = FW_DEVICE_QUIRK_ACK_PACKET_WITH_INVALID_PENDING_CODE,
                        .matches = motu_audio_express_matches,
                        .match_count = ARRAY_SIZE(motu_audio_express_matches),
                },
                {
                        .quirk = FW_DEVICE_QUIRK_UNSTABLE_AT_S400,
                        .matches = tascam_fw_series_matches,
                        .match_count = ARRAY_SIZE(tascam_fw_series_matches),
                },
        };
        int quirks = 0;
        int i;

        for (i = 0; i < ARRAY_SIZE(entries); ++i) {
                int j;

                entry = entries + i;
                for (j = 0; j < entry->match_count; ++j) {
                        unsigned int index = entry->matches[j].index;
                        unsigned int value = entry->matches[j].value;

                        if ((length < index) || (root_directory[index] != value))
                                break;
                }
                if (j == entry->match_count)
                        quirks |= entry->quirk;
        }

        return quirks;
}

static int read_rom(struct fw_device *device, int generation, int speed, 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, speed, offset, data, 4);
                if (rcode != RCODE_BUSY)
                        break;
                msleep(i);
        }
        be32_to_cpus(data);

        return rcode;
}

// By quadlet unit.
#define MAX_CONFIG_ROM_SIZE     ((CSR_CONFIG_ROM_END - CSR_CONFIG_ROM) / sizeof(u32))

/*
 * 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 *new_rom, *old_rom __free(kfree) = NULL;
        u32 *stack, *rom __free(kfree) = NULL;
        u32 sp, key;
        int i, end, length, ret, speed;
        int quirks;

        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);

        speed = SCODE_100;

        /* First read the bus info block. */
        for (i = 0; i < 5; i++) {
                ret = read_rom(device, generation, speed, i, &rom[i]);
                if (ret != RCODE_COMPLETE)
                        return ret;
                /*
                 * 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)
                        return RCODE_BUSY;
        }

        quirks = detect_quirks_by_bus_information_block(rom);

        // Just prevent from torn writing/reading.
        WRITE_ONCE(device->quirks, quirks);

        /*
         * 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))
                        return -ENXIO;

                /* Read header quadlet for the block to get the length. */
                ret = read_rom(device, generation, speed, i, &rom[i]);
                if (ret != RCODE_COMPLETE)
                        return ret;
                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, speed, i, &rom[i]);
                        if (ret != RCODE_COMPLETE)
                                return ret;

                        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;
        }

        quirks |= detect_quirks_by_root_directory(rom + ROOT_DIR_OFFSET, length - ROOT_DIR_OFFSET);

        // Just prevent from torn writing/reading.
        WRITE_ONCE(device->quirks, quirks);

        if (unlikely(quirks & FW_DEVICE_QUIRK_UNSTABLE_AT_S400))
                speed = SCODE_200;
        else
                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) < speed || speed == SCODE_BETA || card->beta_repeaters_present) {
                u32 dummy;

                // for S1600 and S3200.
                if (speed == SCODE_BETA)
                        speed = card->link_speed;

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

        device->max_speed = speed;

        old_rom = device->config_rom;
        new_rom = kmemdup(rom, length * 4, GFP_KERNEL);
        if (new_rom == NULL)
                return -ENOMEM;

        scoped_guard(rwsem_write, &fw_device_rwsem) {
                device->config_rom = new_rom;
                device->config_rom_length = length;
        }

        device->max_rec = rom[2] >> 12 & 0xf;
        device->cmc     = rom[2] >> 30 & 1;
        device->irmc    = rom[2] >> 31 & 1;

        return RCODE_COMPLETE;
}

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(const 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[ROOT_DIR_OFFSET]);
        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_obj(*unit);
                if (unit == NULL)
                        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);

                fw_device_get(device);
                if (device_register(&unit->device) < 0) {
                        put_device(&unit->device);
                        continue;
                }
        }
}

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.config_rom/.config_rom_length and
 *     fw_unit.directory, unless those accesses happen at safe occasions
 */
DECLARE_RWSEM(fw_device_rwsem);

DEFINE_XARRAY_ALLOC(fw_device_xa);
int fw_cdev_major;

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

        device = xa_load(&fw_device_xa, MINOR(devt));
        if (device)
                fw_device_get(device);

        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     secs_to_jiffies(3)
#define INITIAL_DELAY   msecs_to_jiffies(500)
#define SHUTDOWN_DELAY  secs_to_jiffies(2)

static void fw_device_shutdown(struct work_struct *work)
{
        struct fw_device *device = from_work(device, work, work.work);

        if (time_is_after_jiffies64(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);

        xa_erase(&fw_device_xa, MINOR(device->device.devt));

        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;

        /*
         * 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.
         */
        scoped_guard(spinlock_irqsave, &card->lock)
                fw_node_set_device(device->node, NULL);

        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(const 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 = from_work(device, work, work.work);

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

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;
                        }
                        fallthrough;    /* 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 int compare_configuration_rom(struct device *dev, const void *data)
{
        const struct fw_device *old = fw_device(dev);
        const u32 *config_rom = data;

        if (!is_fw_device(dev))
                return 0;

        // Compare the bus information block and root_length/root_crc.
        return !memcmp(old->config_rom, config_rom, 6 * 4);
}

static void fw_device_init(struct work_struct *work)
{
        struct fw_device *device = from_work(device, work, work.work);
        struct fw_card *card = device->card;
        struct device *found;
        u32 minor;
        int ret;

        /*
         * All failure paths here call fw_node_set_device(node, 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;
        }

        // 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.
        //
        // serialize config_rom access.
        scoped_guard(rwsem_read, &fw_device_rwsem) {
                found = device_find_child(card->device, device->config_rom,
                                          compare_configuration_rom);
        }
        if (found) {
                struct fw_device *reused = fw_device(found);

                if (atomic_cmpxchg(&reused->state,
                                   FW_DEVICE_GONE,
                                   FW_DEVICE_RUNNING) == FW_DEVICE_GONE) {
                        // serialize node access
                        scoped_guard(spinlock_irq, &card->lock) {
                                struct fw_node *current_node = device->node;
                                struct fw_node *obsolete_node = reused->node;

                                device->node = obsolete_node;
                                fw_node_set_device(device->node, device);
                                reused->node = current_node;
                                fw_node_set_device(reused->node, reused);

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

                                reused->workfn = fw_device_update;
                                fw_schedule_device_work(reused, 0);

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

                        put_device(found);
                        fw_device_release(&device->device);

                        return;
                }

                put_device(found);
        }

        device_initialize(&device->device);

        fw_device_get(device);

        // The index of allocated entry is used for minor identifier of device node.
        ret = xa_alloc(&fw_device_xa, &minor, device, XA_LIMIT(0, MINORMASK), GFP_KERNEL);
        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 initialization 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) {
                device->workfn = fw_device_shutdown;
                fw_schedule_device_work(device, SHUTDOWN_DELAY);
        } else {
                fw_notice(card, "created device %s: GUID %08x%08x, S%d00, quirks %08x\n",
                          dev_name(&device->device),
                          device->config_rom[3], device->config_rom[4],
                          1 << device->max_speed, device->quirks);
                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:
        xa_erase(&fw_device_xa, minor);
 error:
        fw_device_put(device);          // fw_device_xa'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, device->max_speed, 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 = from_work(device, work, 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);
        device->workfn = 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);
}

static void fw_device_workfn(struct work_struct *work)
{
        struct fw_device *device = from_work(device, to_delayed_work(work), work);
        device->workfn(work);
}

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_obj(*device, GFP_ATOMIC);
                if (device == NULL)
                        break;

                /*
                 * Do minimal initialization 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.
                 */
                fw_node_set_device(node, 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.
                 */
                device->workfn = fw_device_init;
                INIT_DELAYED_WORK(&device->work, fw_device_workfn);
                fw_schedule_device_work(device, INITIAL_DELAY);
                break;

        case FW_NODE_INITIATED_RESET:
        case FW_NODE_LINK_ON:
                device = fw_node_get_device(node);
                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) {
                        device->workfn = fw_device_refresh;
                        fw_schedule_device_work(device,
                                device->is_local ? 0 : INITIAL_DELAY);
                }
                break;

        case FW_NODE_UPDATED:
                device = fw_node_get_device(node);
                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) {
                        device->workfn = fw_device_update;
                        fw_schedule_device_work(device, 0);
                }
                break;

        case FW_NODE_DESTROYED:
        case FW_NODE_LINK_OFF:
                if (!fw_node_get_device(node))
                        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 = fw_node_get_device(node);
                if (atomic_xchg(&device->state,
                                FW_DEVICE_GONE) == FW_DEVICE_RUNNING) {
                        device->workfn = fw_device_shutdown;
                        fw_schedule_device_work(device,
                                list_empty(&card->link) ? 0 : SHUTDOWN_DELAY);
                }
                break;
        }
}

#ifdef CONFIG_FIREWIRE_KUNIT_DEVICE_ATTRIBUTE_TEST
#include "device-attribute-test.c"
#endif