linux 设备模型

Linux 设备模型中有最重要的四个基本概念： device bus class
Linux 认为总线是 CPU和其他设备的通信的通道。基于设备模型，linux 认为所有的设备都需要和总线连接.
/**
 * struct bus_type - The bus type of the device
 *
 * @name:    The name of the bus.
 * @dev_name:    Used for subsystems to enumerate devices like ("foo%u", dev->id).
 * @dev_root:    Default device to use as the parent.
 * @bus_attrs:    Default attributes of the bus.
 * @dev_attrs:    Default attributes of the devices on the bus.
 * @drv_attrs:    Default attributes of the device drivers on the bus.
 * @match:    Called, perhaps multiple times, whenever a new device or driver
 *        is added for this bus. It should return a nonzero value if the
 *        given device can be handled by the given driver.
 * @uevent:    Called when a device is added, removed, or a few other things
 *        that generate uevents to add the environment variables.
 * @probe:    Called when a new device or driver add to this bus, and callback
 *        the specific driver's probe to initial the matched device.
 * @remove:    Called when a device removed from this bus.
 * @shutdown:    Called at shut-down time to quiesce the device.
 * @suspend:    Called when a device on this bus wants to go to sleep mode.
 * @resume:    Called to bring a device on this bus out of sleep mode.
 * @pm:        Power management operations of this bus, callback the specific
 *        device driver's pm-ops.
 * @iommu_ops:  IOMMU specific operations for this bus, used to attach IOMMU
 *              driver implementations to a bus and allow the driver to do
 *              bus-specific setup
 * @p:        The private data of the driver core, only the driver core can
 *        touch this.
 *
 * A bus is a channel between the processor and one or more devices. For the
 * purposes of the device model, all devices are connected via a bus, even if
 * it is an internal, virtual, "platform" bus. Buses can plug into each other.
 * A USB controller is usually a PCI device, for example. The device model
 * represents the actual connections between buses and the devices they control.
 * A bus is represented by the bus_type structure. It contains the name, the
 * default attributes, the bus' methods, PM operations, and the driver core's
 * private data.
 */
struct bus_type {
    const char        *name;
    const char        *dev_name;
    struct device        *dev_root;
    struct bus_attribute    *bus_attrs;
    struct device_attribute    *dev_attrs;
    struct driver_attribute    *drv_attrs;

    int (*match)(struct device *dev, struct device_driver *drv);
    int (*uevent)(struct device *dev, struct kobj_uevent_env *env);
    int (*probe)(struct device *dev);
    int (*remove)(struct device *dev);
    void (*shutdown)(struct device *dev);

    int (*suspend)(struct device *dev, pm_message_t state);
    int (*resume)(struct device *dev);

    const struct dev_pm_ops *pm;

    struct iommu_ops *iommu_ops;

    struct subsys_private *p;
    struct lock_class_key lock_key;
};
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