/**
 * struct device - The basic device structure
 * @parent:     The device's "parent" device, the device to which it is attached.
 *              In most cases, a parent device is some sort of bus or host
 *              controller. If parent is NULL, the device, is a top-level device,
 *              which is not usually what you want.
 * @p:          Holds the private data of the driver core portions of the device.
 *              See the comment of the struct device_private for detail.
 * @kobj:       A top-level, abstract class from which other classes are derived.
 * @init_name:  Initial name of the device.
 * @type:       The type of device.
 *              This identifies the device type and carries type-specific
 *              information.
 * @mutex:      Mutex to synchronize calls to its driver.
 * @bus:        Type of bus device is on.
 * @driver:     Which driver has allocated this
 * @platform_data: Platform data specific to the device.
 *              Example: For devices on custom boards, as typical of embedded
 *              and SOC based hardware, Linux often uses platform_data to point
 *              to board-specific structures describing devices and how they
 *              are wired.  That can include what ports are available, chip
 *              variants, which GPIO pins act in what additional roles, and so
 *              on.  This shrinks the "Board Support Packages" (BSPs) and
 *              minimizes board-specific #ifdefs in drivers.
 * @power:      For device power management.
 *              See Documentation/power/devices.txt for details.
 * @pm_domain:  Provide callbacks that are executed during system suspend,
 *              hibernation, system resume and during runtime PM transitions
 *              along with subsystem-level and driver-level callbacks.
 * @numa_node:  NUMA node this device is close to.
 * @dma_mask:   Dma mask (if dma'ble device).
 * @coherent_dma_mask: Like dma_mask, but for alloc_coherent mapping as not all
 *              hardware supports 64-bit addresses for consistent allocations
 *              such descriptors.
 * @dma_parms:  A low level driver may set these to teach IOMMU code about
 *              segment limitations.
 * @dma_pools:  Dma pools (if dma'ble device).
 * @dma_mem:    Internal for coherent mem override.
 * @archdata:   For arch-specific additions.
 * @of_node:    Associated device tree node.
 * @devt:       For creating the sysfs "dev".
 * @id:         device instance
 * @devres_lock: Spinlock to protect the resource of the device.
 * @devres_head: The resources list of the device.
 * @knode_class: The node used to add the device to the class list.
 * @class:      The class of the device.
 * @groups:     Optional attribute groups.
 * @release:    Callback to free the device after all references have
 *              gone away. This should be set by the allocator of the
 *              device (i.e. the bus driver that discovered the device).
 *
 * At the lowest level, every device in a Linux system is represented by an

 * instance of struct device. The device structure contains the information

 * that the device model core needs to model the system. Most subsystems,
 * however, track additional information about the devices they host. As a
 * result, it is rare for devices to be represented by bare device structures;
 * instead, that structure, like kobject structures, is usually embedded within
 * a higher-level representation of the device.
 */

struct device {
        struct device           *parent;


        struct device_private   *p;


        struct kobject kobj;
        const char              *init_name; /* initial name of the device */
        const struct device_type *type;


        struct mutex            mutex;  /* mutex to synchronize calls to
                                         * its driver.
                                         */


        struct bus_type *bus;           /* type of bus device is on */
        struct device_driver *driver;   /* which driver has allocated this
                                           device */
        void            *platform_data; /* Platform specific data, device
                                           core doesn't touch it */
        struct dev_pm_info      power;
        struct dev_pm_domain    *pm_domain;


#ifdef CONFIG_NUMA
        int             numa_node;      /* NUMA node this device is close to */
#endif
        u64             *dma_mask;      /* dma mask (if dma'able device) */
        u64             coherent_dma_mask;/* Like dma_mask, but for
                                             alloc_coherent mappings as
                                             not all hardware supports
                                             64 bit addresses for consistent
                                             allocations such descriptors. */


        struct device_dma_parameters *dma_parms;


        struct list_head        dma_pools;      /* dma pools (if dma'ble) */


        struct dma_coherent_mem *dma_mem; /* internal for coherent mem
                                             override */
        /* arch specific additions */
        struct dev_archdata     archdata;


        struct device_node      *of_node; /* associated device tree node */


        dev_t                   devt;   /* dev_t, creates the sysfs "dev" */
        u32                     id;     /* device instance */


        spinlock_t              devres_lock;
        struct list_head        devres_head;


        struct klist_node       knode_class;
        struct class            *class;
        const struct attribute_group **groups;  /* optional groups */


        void    (*release)(struct device *dev);
};