从零开始之驱动发开、linux驱动（五十六、linux4.19的IIC驱动adaptor的注册）

 

上一节我们看到下面这函数了。

/**
 * i2c_add_adapter - declare i2c adapter, use dynamic bus number
 * @adapter: the adapter to add
 * Context: can sleep
 *
 * This routine is used to declare an I2C adapter when its bus number
 * doesn't matter or when its bus number is specified by an dt alias.
 * Examples of bases when the bus number doesn't matter: I2C adapters
 * dynamically added by USB links or PCI plugin cards.
 *
 * When this returns zero, a new bus number was allocated and stored
 * in adap->nr, and the specified adapter became available for clients.
 * Otherwise, a negative errno value is returned.
 */
int i2c_add_adapter(struct i2c_adapter *adapter)
{
	struct device *dev = &adapter->dev;
	int id;

	if (dev->of_node) {
		id = of_alias_get_id(dev->of_node, "i2c");
		if (id >= 0) {
			adapter->nr = id;
			return __i2c_add_numbered_adapter(adapter);
		}
	}

	mutex_lock(&core_lock);
	id = idr_alloc(&i2c_adapter_idr, adapter,
		       __i2c_first_dynamic_bus_num, 0, GFP_KERNEL);
	mutex_unlock(&core_lock);
	if (WARN(id < 0, "couldn't get idr"))
		return id;

	adapter->nr = id;

	return i2c_register_adapter(adapter);
}

这个函数作用比较简单，如果这个i2c总线控制器是通过设备树来匹配的。那么就首选从别名列表中，找一下，看是不是有这个i2c总线控制器的别名。有的话，这里id，就直接用别名的id。

如果不是设备树匹配到的，或者别名列表中没有这个设备，那就只能从__i2c_first_dynamic_bus_num往后查找一个没用的编号使用了。

__i2c_first_dynamic_bus_num的意思也很明显，第一个动态查找的总线编号。主要就是从idr中它这个位置开始找空闲编号。idr当然还有一个作用就是记录好adapter。使在i2c_adapter_idr为树根的idr中，id和adapter一一对应。

 

前面已经找到adap可以在idr中放的位置了，那么这里只要把这个指针放进去就可以了。

/**
 * __i2c_add_numbered_adapter - i2c_add_numbered_adapter where nr is never -1
 * @adap: the adapter to register (with adap->nr initialized)
 * Context: can sleep
 *
 * See i2c_add_numbered_adapter() for details.
 */
static int __i2c_add_numbered_adapter(struct i2c_adapter *adap)
{
	int id;

	mutex_lock(&core_lock);
	id = idr_alloc(&i2c_adapter_idr, adap, adap->nr, adap->nr + 1, GFP_KERNEL);
	mutex_unlock(&core_lock);
	if (WARN(id < 0, "couldn't get idr"))
		return id == -ENOSPC ? -EBUSY : id;

	return i2c_register_adapter(adap);
}

最后就是注册这个适配器了。

 

static int i2c_register_adapter(struct 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;

	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 = of_i2c_setup_smbus_alert(adap);
	if (res)
		goto out_reg;

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

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

#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

	i2c_init_recovery(adap);

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

 

 

这里主要说一下之前没说过的内容。

第一点就是给这个i2c控制注册一个irq_domain

	/* register soft irqs for Host Notify */
	res = i2c_setup_host_notify_irq_domain(adap);

当然这个irq_domain注册是有条件的，就是要这个i2c控制器要有I2C_FUNC_SMBUS_HOST_NOTIFY功能，很明显，我们的是没有的。

那这里的主机通知功能的中断就注册不了。

static int i2c_setup_host_notify_irq_domain(struct i2c_adapter *adap)
{
	struct irq_domain *domain;

	if (!i2c_check_functionality(adap, I2C_FUNC_SMBUS_HOST_NOTIFY))
		return 0;

	domain = irq_domain_create_linear(adap->dev.fwnode,
					  I2C_ADDR_7BITS_COUNT,
					  &i2c_host_notify_irq_ops, adap);
	if (!domain)
		return -ENOMEM;

	adap->host_notify_domain = domain;

	return 0;
}

 

第二点

我们.config是没这个CONFIG_I2C_SMBUS，同时设备树文件也是没smbus_alert属性值的

#if IS_ENABLED(CONFIG_I2C_SMBUS) && IS_ENABLED(CONFIG_OF)
int of_i2c_setup_smbus_alert(struct i2c_adapter *adapter)
{
	struct i2c_client *client;
	int irq;

	irq = of_property_match_string(adapter->dev.of_node, "interrupt-names",
				       "smbus_alert");
	if (irq == -EINVAL || irq == -ENODATA)
		return 0;
	else if (irq < 0)
		return irq;

	client = i2c_setup_smbus_alert(adapter, NULL);
	if (!client)
		return -ENODEV;

	return 0;
}
#endif

 

 

第三点，i2c总线有故障后，进行自我恢复的初始化。

目前来看，内核中这个用的还是比较少。

static void i2c_init_recovery(struct i2c_adapter *adap)
{
	struct i2c_bus_recovery_info *bri = adap->bus_recovery_info;
	char *err_str;

	if (!bri)
		return;

	if (!bri->recover_bus) {
		err_str = "no recover_bus() found";
		goto err;
	}

	if (bri->scl_gpiod && bri->recover_bus == i2c_generic_scl_recovery) {
		bri->get_scl = get_scl_gpio_value;
		bri->set_scl = set_scl_gpio_value;
		if (bri->sda_gpiod) {
			bri->get_sda = get_sda_gpio_value;
			/* FIXME: add proper flag instead of '0' once available */
			if (gpiod_get_direction(bri->sda_gpiod) == 0)
				bri->set_sda = set_sda_gpio_value;
		}
		return;
	}

	if (bri->recover_bus == i2c_generic_scl_recovery) {
		/* Generic SCL recovery */
		if (!bri->set_scl || !bri->get_scl) {
			err_str = "no {get|set}_scl() found";
			goto err;
		}
		if (!bri->set_sda && !bri->get_sda) {
			err_str = "either get_sda() or set_sda() needed";
			goto err;
		}
	}

	return;
 err:
	dev_err(&adap->dev, "Not using recovery: %s\n", err_str);
	adap->bus_recovery_info = NULL;
}

 

第四点，也是做重要的一点

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

 

就是，这个i2c总线下的设备怎么处理。

在没设备树的内核是在mach-xxx.c文件中定义，注册

static struct i2c_board_info h4_i2c_board_info[] __initdata = {
	{
		I2C_BOARD_INFO("isp1301_omap", 0x2d),
		.irq		= OMAP_GPIO_IRQ(125),
	},
	{	/* EEPROM on mainboard */
		I2C_BOARD_INFO("24c01", 0x52),
		.platform_data	= &m24c01,
	},
	{	/* EEPROM on cpu card */
		I2C_BOARD_INFO("24c01", 0x57),
		.platform_data	= &m24c01,
	},
};

static void __init omap_h4_init(void)
{
	(...)
	i2c_register_board_info(1, h4_i2c_board_info,
			ARRAY_SIZE(h4_i2c_board_info));
	(...)
}

 

新内核因为设备相关的内容都要移动到设备树了，所以肯定要用设备树来处理了。

 

这个函数就是用来注册总线下的i2c设备的。

 

先看一下设备怎么在总线下放置

&i2c0 {
	status = "okay";

	audio-codec@1b {
		compatible = "wlf,wm8580";
		reg = <0x1b>;
	};

	eeprom@50 {
		compatible = "atmel,24c08";
		reg = <0x50>;
	};
};

看到了设备，如何在总线下放置之后，分析就会简单很多

 

void of_i2c_register_devices(struct i2c_adapter *adap)
{
	struct device_node *bus, *node;
	struct i2c_client *client;

	/* Only register child devices if the adapter has a node pointer set */
	if (!adap->dev.of_node)
		return;

	dev_dbg(&adap->dev, "of_i2c: walking child nodes\n");

    /* 获取总线 */
	bus = of_get_child_by_name(adap->dev.of_node, "i2c-bus");
	if (!bus)
		bus = of_node_get(adap->dev.of_node);

    /* 遍历总线节点下的子节点 */
	for_each_available_child_of_node(bus, node) {
		if (of_node_test_and_set_flag(node, OF_POPULATED))    //如果这个节点已经创建节点，这里就不再创建
			continue;

        /* 使用这个总线节点里的子节点注册一个i2c_client */
		client = of_i2c_register_device(adap, node);
		if (IS_ERR(client)) {
			dev_err(&adap->dev,
				 "Failed to create I2C device for %pOF\n",
				 node);
			of_node_clear_flag(node, OF_POPULATED);
		}
	}

	of_node_put(bus);
}

 

static struct i2c_client *of_i2c_register_device(struct i2c_adapter *adap,
						 struct device_node *node)
{
	struct i2c_client *client;
	struct i2c_board_info info;
	int ret;

	dev_dbg(&adap->dev, "of_i2c: register %pOF\n", node);

    /* 获取设备信息 */
	ret = of_i2c_get_board_info(&adap->dev, node, &info);
	if (ret)
		return ERR_PTR(ret);

    /* 注册一个设备 */
	client = i2c_new_device(adap, &info);
	if (!client) {
		dev_err(&adap->dev, "of_i2c: Failure registering %pOF\n", node);
		return ERR_PTR(-EINVAL);
	}
	return client;
}

 

设备信息就比较简单了，名字，i2c从机的地址

int of_i2c_get_board_info(struct device *dev, struct device_node *node,
			  struct i2c_board_info *info)
{
	u32 addr;
	int ret;

	memset(info, 0, sizeof(*info));

    /* 获取名字 */
	if (of_modalias_node(node, info->type, sizeof(info->type)) < 0) {
		dev_err(dev, "of_i2c: modalias failure on %pOF\n", node);
		return -EINVAL;
	}

    /* 获取从机地址 */
	ret = of_property_read_u32(node, "reg", &addr);
	if (ret) {
		dev_err(dev, "of_i2c: invalid reg on %pOF\n", node);
		return ret;
	}

    /* 根据地址,设备client的标志 */
	if (addr & I2C_TEN_BIT_ADDRESS) {
		addr &= ~I2C_TEN_BIT_ADDRESS;
		info->flags |= I2C_CLIENT_TEN;
	}

	if (addr & I2C_OWN_SLAVE_ADDRESS) {
		addr &= ~I2C_OWN_SLAVE_ADDRESS;
		info->flags |= I2C_CLIENT_SLAVE;
	}

	info->addr = addr;
	info->of_node = node;

	if (of_property_read_bool(node, "host-notify"))
		info->flags |= I2C_CLIENT_HOST_NOTIFY;

	if (of_get_property(node, "wakeup-source", NULL))
		info->flags |= I2C_CLIENT_WAKE;

	return 0;
}