platform_bus_init過程

    文章的分析基於linux-2.6.22

    今天記錄下 platform_bus_init過程中，platform_bus_type總線和platform_bus設備的註冊，以及構建的目錄結構。

1.
/**
 *	driver_init - initialize driver model.
 *
 *	Call the driver model init functions to initialize their
 *	subsystems. Called early from init/main.c.
 */

void __init driver_init(void)
{
        ......

	platform_bus_init();

        ......
}


2.
int __init platform_bus_init(void)
{
	int error;

	error = device_register(&platform_bus); //2.1分析
	if (error)
		return error;
	error =  bus_register(&platform_bus_type); //2.2分析
	if (error)
		device_unregister(&platform_bus);
	return error;
}

struct device platform_bus = {
	.bus_id		= "platform",
};

struct bus_type platform_bus_type = {
	.name		= "platform",
	.dev_attrs	= platform_dev_attrs,
	.match		= platform_match,
	.uevent		= platform_uevent,
	.suspend	= platform_suspend,
	.suspend_late	= platform_suspend_late,
	.resume_early	= platform_resume_early,
	.resume		= platform_resume,
};


2.1
/**
 *	device_register - register a device with the system.
 *	@dev:	pointer to the device structure
 *
 *	This happens in two clean steps - initialize the device
 *	and add it to the system. The two steps can be called
 *	separately, but this is the easiest and most common.
 *	I.e. you should only call the two helpers separately if
 *	have a clearly defined need to use and refcount the device
 *	before it is added to the hierarchy.
 */

int device_register(struct device *dev)
{
	device_initialize(dev); //2.1.1分析
	return device_add(dev); //2.1.2分析
}


2.1.1
/**
 *	device_initialize - init device structure.
 *	@dev:	device.
 *
 *	This prepares the device for use by other layers,
 *	including adding it to the device hierarchy.
 *	It is the first half of device_register(), if called by
 *	that, though it can also be called separately, so one
 *	may use @dev's fields (e.g. the refcount).
 */

//devices_subsys的目錄名爲devices
void device_initialize(struct device *dev)
{
        ......	

        kobj_set_kset_s(dev, devices_subsys); //設置dev的kset指向devices_subsys
     
        .......

	INIT_LIST_HEAD(&dev->node);

	.......
}


2.1.2
/**
 *	device_add - add device to device hierarchy.
 *	@dev:	device.
 *
 *	This is part 2 of device_register(), though may be called
 *	separately _iff_ device_initialize() has been called separately.
 *
 *	This adds it to the kobject hierarchy via kobject_add(), adds it
 *	to the global and sibling lists for the device, then
 *	adds it to the other relevant subsystems of the driver model.
 */
int device_add(struct device *dev)
{
        ......

        kobject_set_name(&dev->kobj, "%s", dev->bus_id);
	error = kobject_add(&dev->kobj); //設置dev的parent，將其加人devices_subsys的鏈表

        ......
}


2.2
/**
 *	bus_register - register a bus with the system.
 *	@bus:	bus.
 *
 *	Once we have that, we registered the bus with the kobject
 *	infrastructure, then register the children subsystems it has:
 *	the devices and drivers that belong to the bus.
 */

//bus_subsys的目錄名爲bus
int bus_register(struct bus_type * bus)
{
        ......

        retval = kobject_set_name(&bus->subsys.kobj, "%s", bus->name);

        ......

        subsys_set_kset(bus, bus_subsys); //設置bus的kset的指向bus_subsys
	retval = subsystem_register(&bus->subsys); //設置bus->subsys的parent，將其加入
                                                   //bus_subsys的鏈表

        ......
        
        kobject_set_name(&bus->devices.kobj, "devices");
	bus->devices.kobj.parent = &bus->subsys.kobj;
	retval = kset_register(&bus->devices);
        ......

	kobject_set_name(&bus->drivers.kobj, "drivers");
	bus->drivers.kobj.parent = &bus->subsys.kobj;
	bus->drivers.ktype = &ktype_driver;
	retval = kset_register(&bus->drivers);
	......

	klist_init(&bus->klist_devices, klist_devices_get, klist_devices_put);
	klist_init(&bus->klist_drivers, NULL, NULL);

	bus->drivers_autoprobe = 1;        
}

圖1：platform_bus和devices_subsys數據結構連接的簡單示意，程序的2.1部分建立的devices/platform文件夾

 

 

圖2：platform_bus_type和bus_subsys數據結構連接的簡單示意，程序的2.2部分建立的bus/platform文件夾，然後創建了platform/devices和platform/drives