linux驱动之platform_bus_init-2

linux驱动之platform_bus_init() 2

代码drivers/base/platform.c drivers/base/bus.c

分析bus_register()

int __init platform_bus_init(void)
{
	int error;
	early_platform_cleanup();
	error = device_register(&platform_bus);
	...
	error =  bus_register(&platform_bus_type);
	...
	of_platform_register_reconfig_notifier();
	return error;
}

struct bus_type platform_bus_type = {
	.name		= "platform", 
	.dev_groups	= platform_dev_groups,
	.match		= platform_match,
	.uevent		= platform_uevent,
	.pm		= &platform_dev_pm_ops,
};
struct subsys_private {
	struct kset subsys;
	struct kset *devices_kset;
	struct list_head interfaces;
	struct mutex mutex;

	struct kset *drivers_kset;
	struct klist klist_devices;
	struct klist klist_drivers;
	struct blocking_notifier_head bus_notifier;
	unsigned int drivers_autoprobe:1;
	struct bus_type *bus;

	struct kset glue_dirs;
	struct class *class;
};

int bus_register(struct bus_type *bus)
{
	int retval;
	struct subsys_private *priv;
	...
	priv = kzalloc(sizeof(struct subsys_private), GFP_KERNEL);
	...
	//互相记录指针
	priv->bus = bus;
	bus->p = priv;

	//bus上事件的通知链表
	BLOCKING_INIT_NOTIFIER_HEAD(&priv->bus_notifier);

	//kobj代表/sys中一个目录,bus本身没有kobj
	//subsys_private中保存bus的一些私有信息
	//设置name = "platform",也是/sys/bus/platform
	retval = kobject_set_name(&priv->subsys.kobj, "%s", bus->name);
	...
	//bus_kset是/sys/bus
	priv->subsys.kobj.kset = bus_kset;
	priv->subsys.kobj.ktype = &bus_ktype;
	//drivers和devices自动匹配,并调用drivers->probe()
	priv->drivers_autoprobe = 1;

	//创建/sys/bus/platform
	retval = kset_register(&priv->subsys);
	...
	//生成/sys/bus/platform/uevent文件
	retval = bus_create_file(bus, &bus_attr_uevent);
	...
	//生成/sys/bus/platform/devices目录
	//目录下是挂在bus的设备,是/sys/devices/platform/下设备的软连接
	priv->devices_kset = kset_create_and_add("devices", NULL,
						 &priv->subsys.kobj);
	...
	//生成/sys/bus/platform/drivers目录
	//目录下是挂在bus的drivers,是/sys/devices/platform/下drivers的软连接
	priv->drivers_kset = kset_create_and_add("drivers", NULL,
						 &priv->subsys.kobj);
	...
	INIT_LIST_HEAD(&priv->interfaces);
	__mutex_init(&priv->mutex, "subsys mutex", key);
	//挂在bus上的devices
	klist_init(&priv->klist_devices, klist_devices_get, klist_devices_put);
	//挂在bus上的drivers
	klist_init(&priv->klist_drivers, NULL, NULL);

	//创建/sys/bus/platform/drivers_autoprobe属性文件
	//创建/sys/bus/platform/drivers_probe属性文件
	retval = add_probe_files(bus);
	...
	//platform没有bus_groups
	retval = bus_add_groups(bus, bus->bus_groups);
	...
	return 0;
	...
}

生成/sys/bus/platform/uevent文件
这是只写的文件,用于手动添加kobj事件

static ssize_t bus_uevent_store(struct bus_type *bus,
				const char *buf, size_t count)
{
	enum kobject_action action;

	if (kobject_action_type(buf, count, &action) == 0)
		kobject_uevent(&bus->p->subsys.kobj, action);
	return count;
}
static BUS_ATTR(uevent, S_IWUSR, NULL, bus_uevent_store);

//写入devices的name手动进行匹配
static ssize_t store_drivers_probe(struct bus_type *bus,
				   const char *buf, size_t count)
{
	struct device *dev;
	int err = -EINVAL;

	dev = bus_find_device_by_name(bus, NULL, buf);
	...
	if (bus_rescan_devices_helper(dev, NULL) == 0)
		err = count;
	put_device(dev);
	return err;
}
static BUS_ATTR(drivers_probe, S_IWUSR, NULL, store_drivers_probe);

//设置bus->p->drivers_autoprobe,表示是否自动匹配:
//devices或drivers注册时,自动调用bus->match()进行匹配
static BUS_ATTR(drivers_autoprobe, S_IWUSR | S_IRUGO,
		show_drivers_autoprobe, store_drivers_autoprobe);

static int add_probe_files(struct bus_type *bus)
{
	int retval;
	retval = bus_create_file(bus, &bus_attr_drivers_probe);
	...
	retval = bus_create_file(bus, &bus_attr_drivers_autoprobe);
	...
	return retval;
}