---
name: "struct_device"
section: "9"
platform: "linux"
package: "linux-manual-3.16"
version: "3.16.56-1+deb8u1"
release: "Debian 8 (Jessie)"
platforms: ["linux"]
url: "https://new.carta.tech/struct_device"
---

# struct\_device(9)

The basic device structure

## NAME

struct\_device - The basic device structure

## SYNOPSIS

```
struct device {
  struct device * parent;
  struct device_private * p;
  struct kobject kobj;
  const char * init_name;
  const struct device_type * type;
  struct mutex mutex;
  struct bus_type * bus;
  struct device_driver * driver;
  void * platform_data;
  void * driver_data;
  struct dev_pm_info power;
  struct dev_pm_domain * pm_domain;
#ifdef CONFIG_PINCTRL
  struct dev_pin_info * pins;
#endif
#ifdef CONFIG_NUMA
  int numa_node;
#endif
  u64 * dma_mask;
  u64 coherent_dma_mask;
  unsigned long dma_pfn_offset;
  struct device_dma_parameters * dma_parms;
  struct list_head dma_pools;
  struct dma_coherent_mem * dma_mem;
#ifdef CONFIG_DMA_CMA
  struct cma * cma_area;
#endif
  struct dev_archdata archdata;
  struct device_node * of_node;
  struct acpi_dev_node acpi_node;
  dev_t devt;
  u32 id;
  spinlock_t devres_lock;
  struct list_head devres_head;
  struct klist_node knode_class;
  struct class * class;
  const struct attribute_group ** groups;
  void (* release) (struct device *dev);
  struct iommu_group * iommu_group;
  bool offline_disabled:1;
  bool offline:1;
};
```

## MEMBERS

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.

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.

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.

acpi\_node

Associated ACPI device 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).

iommu\_group

IOMMU group the device belongs to.

offline\_disabled

If set, the device is permanently online.

offline

Set after successful invocation of bus type's .**offline**.

## 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.
```

## DESCRIPTION

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.

## COPYRIGHT