text: // 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/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;
  }
  
  /**
   * 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 after
   * the immediate entry with @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(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 const struct ieee1394_device_id *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};
  
  	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(struct device *dev);
  
  static int fw_unit_match(struct device *dev, 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 int fw_unit_remove(struct device *dev)
  {
  	struct fw_driver *driver =
  			container_of(dev->driver, struct fw_driver, driver);
  
  	return driver->remove(fw_unit(dev)), 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,
  	.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 *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)
  			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));
  
  		old->workfn = 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);
  	minor = idr_alloc(&fw_device_idr, device, 0, 1 << MINORBITS,
  			GFP_KERNEL);
  	up_write(&fw_device_rwsem);
  
  	if (minor < 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\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);
  	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 = container_of(to_delayed_work(work),
  						struct fw_device, 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(sizeof(*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.
  		 */
  		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.
  		 */
  		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 = 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) {
  			device->workfn = 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) {
  			device->workfn = 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) {
  			device->workfn = fw_device_shutdown;
  			fw_schedule_device_work(device,
  				list_empty(&card->link) ? 0 : SHUTDOWN_DELAY);
  		}
  		break;
  	}
  }
  