Linux USB subsystem-USB Bus Registry

Objective: To study USB in depth and take notes here. Welcome to the discussion.

[Linux 3.2] [Driver/USB/CORE/driver. C]

Definition: usb_bus_type

struct bus_type usb_bus_type = {.name ="usb",.match =usb_device_match,.uevent =usb_uevent,};

 

[Linux 3.2] [Driver/base/bus. C]

Function: bus_register (struct bus_type * Bus)

/** * 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. */int bus_register(struct bus_type *bus){int retval;struct subsys_private *priv;priv = kzalloc(sizeof(struct subsys_private), GFP_KERNEL);if (!priv)return -ENOMEM;priv->bus = bus;bus->p = priv;BLOCKING_INIT_NOTIFIER_HEAD(&priv->bus_notifier);retval = kobject_set_name(&priv->subsys.kobj, "%s", bus->name);if (retval)goto out;priv->subsys.kobj.kset = bus_kset;priv->subsys.kobj.ktype = &bus_ktype;priv->drivers_autoprobe = 1;retval = kset_register(&priv->subsys);if (retval)goto out;retval = bus_create_file(bus, &bus_attr_uevent);if (retval)goto bus_uevent_fail;priv->devices_kset = kset_create_and_add("devices", NULL, &priv->subsys.kobj);if (!priv->devices_kset) {retval = -ENOMEM;goto bus_devices_fail;}priv->drivers_kset = kset_create_and_add("drivers", NULL, &priv->subsys.kobj);if (!priv->drivers_kset) {retval = -ENOMEM;goto bus_drivers_fail;}klist_init(&priv->klist_devices, klist_devices_get, klist_devices_put);klist_init(&priv->klist_drivers, NULL, NULL);retval = add_probe_files(bus);if (retval)goto bus_probe_files_fail;retval = bus_add_attrs(bus);if (retval)goto bus_attrs_fail;pr_debug("bus: '%s': registered\n", bus->name);return 0;bus_attrs_fail:remove_probe_files(bus);bus_probe_files_fail:kset_unregister(bus->p->drivers_kset);bus_drivers_fail:kset_unregister(bus->p->devices_kset);bus_devices_fail:bus_remove_file(bus, &bus_attr_uevent);bus_uevent_fail:kset_unregister(&bus->p->subsys);out:kfree(bus->p);bus->p = NULL;return retval;}EXPORT_SYMBOL_GPL(bus_register);

Bus_register is mainly used to handle Linux device models.

This function has the following functions:

1. Line 21: initialize a blocking notification chain.

2. Line 23 ~ 31: add the USB bus to the bus set and create a USB subdirectory under/sys/bus.

3. Line 35: Create a uevent attribute file under/sys/bus/USB.

4. Line 39 ~ 51: Create devices and drivers Subsets on the USB Bus subset and create directories at the same time.

5. Line 53 ~ 54: Initialize two linked lists: klist_devices and klist_drivers.

6. Line 56: add the drivers_probe and drivers_autoprobe attribute files of the bus. (Support for config_hotplug is required)

7. Line 60: add other property files of the bus. For USB, no.

After completing these steps, you can view the USB directory under/sys/bus,

You can see below the USB directory:

# Ls/sys/bus/USB

Devices drivers_autoprobe uevent drivers drivers_probe