linux kernel device结构分析

/**
 * 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.
 * @driver_data: Private pointer for driver specific info.
 * @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.
 * @pins:    For device pin management.
 *        See Documentation/pinctrl.txt for details.
 * @msi_list:    Hosts MSI descriptors
 * @msi_domain: The generic MSI domain this device is using.
 * @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_pfn_offset: offset of DMA memory range relatively of RAM
 * @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.
 * @cma_area:    Contiguous memory area for dma allocations
 * @archdata:    For arch-specific additions.
 * @of_node:    Associated device tree node.
 * @fwnode:    Associated device node supplied by platform firmware.
 * @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).
 * @iommu_grou