i2c bus 路径

struct bus_type i2c_bus_type = {
	.name		= "i2c",
	.match		= i2c_device_match,
	.probe		= i2c_device_probe,
	.remove		= i2c_device_remove,
	.shutdown	= i2c_device_shutdown,
};
EXPORT_SYMBOL_GPL(i2c_bus_type);

static int __init i2c_init(void)
{
	int retval;

	retval = of_alias_get_highest_id("i2c");

	down_write(&__i2c_board_lock);
	if (retval >= __i2c_first_dynamic_bus_num)
		__i2c_first_dynamic_bus_num = retval + 1;
	up_write(&__i2c_board_lock);

	retval = bus_register(&i2c_bus_type);
	if (retval)
		return retval;

	is_registered = true;

#ifdef CONFIG_I2C_COMPAT
	i2c_adapter_compat_class = class_compat_register("i2c-adapter");
	if (!i2c_adapter_compat_class) {
		retval = -ENOMEM;
		goto bus_err;
	}
#endif
	retval = i2c_add_driver(&dummy_driver);
	if (retval)
		goto class_err;

	if (IS_ENABLED(CONFIG_OF_DYNAMIC))
		WARN_ON(of_reconfig_notifier_register(&i2c_of_notifier));
	if (IS_ENABLED(CONFIG_ACPI))
		WARN_ON(acpi_reconfig_notifier_register(&i2c_acpi_notifier));

	return 0;

class_err:
#ifdef CONFIG_I2C_COMPAT
	class_compat_unregister(i2c_adapter_compat_class);
bus_err:
#endif
	is_registered = false;
	bus_unregister(&i2c_bus_type);
	return retval;
}

结合 .name = “i2c”, retval = bus_register(&i2c_bus_type);
这表明命名是 “i2c”，通过bus_register注册到bus 总线目录下。

实际如下图

i2c adaptor 路径

static int i2c_register_adapter(struc
t i2c_adapter *adap)
{
	int res = -EINVAL;

	/* Can't register until after driver model init */
	if (WARN_ON(!is_registered)) {
		res = -EAGAIN;
		goto out_list;
	}

	/* Sanity checks */
	if (WARN(!adap->name[0], "i2c adapter has no name"))
		goto out_list;

	if (!adap->algo) {
		pr_err("adapter '%s': no algo supplied!\n", adap->name);
		goto out_list;
	}

	if (!adap->lock_ops)
		adap->lock_ops = &i2c_adapter_lock_ops;

	adap->locked_flags = 0;
	rt_mutex_init(&adap->bus_lock);
	rt_mutex_init(&adap->mux_lock);
	mutex_init(&adap->userspace_clients_lock);
	INIT_LIST_HEAD(&adap->userspace_clients);

	/* Set default timeout to 1 second if not already set */
	if (adap->timeout == 0)
		adap->timeout = HZ;

	/* register soft irqs for Host Notify */
	res = i2c_setup_host_notify_irq_domain(adap);
	if (res) {
		pr_err("adapter '%s': can't create Host Notify IRQs (%d)\n",
		       adap->name, res);
		goto out_list;
	}

	dev_set_name(&adap->dev, "i2c-%d", adap->nr);
	adap->dev.bus = &i2c_bus_type;
	adap->dev.type = &i2c_adapter_type;
	res = device_register(&adap->dev);
	if (res) {
		pr_err("adapter '%s': can't register device (%d)\n", adap->name, res);
		goto out_list;
	}

	res = i2c_setup_smbus_alert(adap);
	if (res)
		goto out_reg;

	device_enable_async_suspend(&adap->dev);
	pm_runtime_no_callbacks(&adap->dev);
	pm_suspend_ignore_children(&adap->dev, true);
	pm_runtime_enable(&adap->dev);

	res = i2c_init_recovery(adap);
	if (res == -EPROBE_DEFER)
		goto out_reg;

	dev_dbg(&adap->dev, "adapter [%s] registered\n", adap->name);

#ifdef CONFIG_I2C_COMPAT
	res = class_compat_create_link(i2c_adapter_compat_class, &adap->dev,
				       adap->dev.parent);
	if (res)
		dev_warn(&adap->dev,
			 "Failed to create compatibility class link\n");
#endif

	/* create pre-declared device nodes */
	of_i2c_register_devices(adap);
	i2c_acpi_install_space_handler(adap);
	i2c_acpi_register_devices(adap);

	if (adap->nr < __i2c_first_dynamic_bus_num)
		i2c_scan_static_board_info(adap);

	/* Notify drivers */
	mutex_lock(&core_lock);
	bus_for_each_drv(&i2c_bus_type, NULL, adap, __process_new_adapter);
	mutex_unlock(&core_lock);

	return 0;

out_reg:
	init_completion(&adap->dev_released);
	device_unregister(&adap->dev);
	wait_for_completion(&adap->dev_released);
out_list:
	mutex_lock(&core_lock);
	idr_remove(&i2c_adapter_idr, adap->nr);
	mutex_unlock(&core_lock);
	return res;
}

通过这2行
dev_set_name(&adap->dev, “i2c-%d”, adap->nr);
adap->dev.bus = &i2c_bus_type;

表明适配器的路径在bus 路径的devices下面。命名风格是"i2c-%d"，%d是注册的适配器的总线号。实际如下图

i2c client路径

struct i2c_client *
i2c_new_client_device(struct i2c_adapter *adap, struct i2c_board_info const *info)
{
	struct i2c_client	*client;
	int			status;
	client = kzalloc(sizeof *client, GFP_KERNEL);
	if (!client)
		return ERR_PTR(-ENOMEM);
	client->adapter = adap;
	client->dev.platform_data = info->platform_data;
	client->flags = info->flags;
	client->addr = info->addr;
	client->init_irq = info->irq;
	if (!client->init_irq)
		client->init_irq = i2c_dev_irq_from_resources(info->resources,
							 info->num_resources);
	strscpy(client->name, info->type, sizeof(client->name));
	status = i2c_check_addr_validity(client->addr, client->flags);
	if (status) {
		dev_err(&adap->dev, "Invalid %d-bit I2C address 0x%02hx\n",
			client->flags & I2C_CLIENT_TEN ? 10 : 7, client->addr);
		goto out_err_silent;
	}
	/* Check for address business */
	status = i2c_check_addr_busy(adap, i2c_encode_flags_to_addr(client));
	if (status)
		goto out_err;
	client->dev.parent = &client->adapter->dev;
	client->dev.bus = &i2c_bus_type;
	client->dev.type = &i2c_client_type;
	client->dev.of_node = of_node_get(info->of_node);
	client->dev.fwnode = info->fwnode;
	device_enable_async_suspend(&client->dev);
	i2c_dev_set_name(adap, client, info);
	if (info->swnode) {
		status = device_add_software_node(&client->dev, info->swnode);
		if (status) {
			dev_err(&adap->dev,
				"Failed to add software node to client %s: %d\n",
				client->name, status);
			goto out_err_put_of_node;
		}
	}
	status = device_register(&client->dev);
	if (status)
		goto out_remove_swnode;
	dev_dbg(&adap->dev, "client [%s] registered with bus id %s\n",
		client->name, dev_name(&client->dev));
	return client;
out_remove_swnode:
	device_remove_software_node(&client->dev);
out_err_put_of_node:
	of_node_put(info->of_node);
out_err:
	dev_err(&adap->dev,
		"Failed to register i2c client %s at 0x%02x (%d)\n",
		client->name, client->addr, status);
out_err_silent:
	kfree(client);
	return ERR_PTR(status);
}
EXPORT_SYMBOL_GPL(i2c_new_client_device);

client->dev.parent = &client->adapter->dev; 表明client 实体对应的device节点在adapter的目录下，命名由 strscpy(client->name, info->type, sizeof(client->name)); 和 i2c_dev_set_name(adap, client, info)这两项决定。

i2c_dev_set_name 的实现如下

static void i2c_dev_set_name(struct i2c_adapter *adap,
			     struct i2c_client *client,
			     struct i2c_board_info const *info)
{
	struct acpi_device *adev = ACPI_COMPANION(&client->dev);

	if (info && info->dev_name) {
		dev_set_name(&client->dev, "i2c-%s", info->dev_name);
		return;
	}

	if (adev) {
		dev_set_name(&client->dev, "i2c-%s", acpi_dev_name(adev));
		return;
	}

	dev_set_name(&client->dev, "%d-%04x", i2c_adapter_id(adap),
		     i2c_encode_flags_to_addr(client));
}

static inline int i2c_adapter_id(struct i2c_adapter *adap)
 {
 	return adap->nr;
 }

static unsigned short i2c_encode_flags_to_addr(struct i2c_client *client)
{
	unsigned short addr = client->addr;

	/* For some client flags, add an arbitrary offset to avoid collisions */
	if (client->flags & I2C_CLIENT_TEN)
		addr |= I2C_ADDR_OFFSET_TEN_BIT;

	if (client->flags & I2C_CLIENT_SLAVE)
		addr |= I2C_ADDR_OFFSET_SLAVE;

	return addr;
}

#define I2C_ADDR_OFFSET_TEN_BIT	0xa000
#define I2C_ADDR_OFFSET_SLAVE	0x1000

实例如下图

上图第一个红框是常规命名方式，下面的是ACPI的命名方式