Device drivers infrastructure¶

The Basic Device Driver-Model Structures¶

struct bus_type¶: The bus type of the device

Definition

struct bus_type {
  const char * name;
  const char * dev_name;
  struct device * dev_root;
  const struct attribute_group ** bus_groups;
  const struct attribute_group ** dev_groups;
  const struct attribute_group ** drv_groups;
  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 (* online) (struct device *dev);
  int (* offline) (struct device *dev);
  int (* suspend) (struct device *dev, pm_message_t state);
  int (* resume) (struct device *dev);
  int (* num_vf) (struct device *dev);
  const struct dev_pm_ops * pm;
  const struct iommu_ops * iommu_ops;
  struct subsys_private * p;
  struct lock_class_key lock_key;
};

Members

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_groups: Default attributes of the bus.
dev_groups: Default attributes of the devices on the bus.
drv_groups: 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 positive value if the given device can be handled by the given driver and zero otherwise. It may also return error code if determining that the driver supports the device is not possible. In case of -EPROBE_DEFER it will queue the device for deferred probing.
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.
online: Called to put the device back online (after offlining it).
offline: Called to put the device offline for hot-removal. May fail.
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.
num_vf: Called to find out how many virtual functions a device on this bus supports.
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.
lock_key: Lock class key for use by the lock validator

Description

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.

enum probe_type¶: device driver probe type to try Device drivers may opt in for special handling of their respective probe routines. This tells the core what to expect and prefer.

Constants

PROBE_DEFAULT_STRATEGY: Used by drivers that work equally well whether probed synchronously or asynchronously.
PROBE_PREFER_ASYNCHRONOUS: Drivers for “slow” devices which probing order is not essential for booting the system may opt into executing their probes asynchronously.
PROBE_FORCE_SYNCHRONOUS: Use this to annotate drivers that need their probe routines to run synchronously with driver and device registration (with the exception of -EPROBE_DEFER handling - re-probing always ends up being done asynchronously).

Description

Note that the end goal is to switch the kernel to use asynchronous probing by default, so annotating drivers with PROBE_PREFER_ASYNCHRONOUS is a temporary measure that allows us to speed up boot process while we are validating the rest of the drivers.

struct device_driver¶: The basic device driver structure

Definition

struct device_driver {
  const char * name;
  struct bus_type * bus;
  struct module * owner;
  const char * mod_name;
  bool suppress_bind_attrs;
  enum probe_type probe_type;
  const struct of_device_id * of_match_table;
  const struct acpi_device_id * acpi_match_table;
  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 attribute_group ** groups;
  const struct dev_pm_ops * pm;
  struct driver_private * p;
};

Members

name: Name of the device driver.
bus: The bus which the device of this driver belongs to.
owner: The module owner.
mod_name: Used for built-in modules.
suppress_bind_attrs: Disables bind/unbind via sysfs.
probe_type: Type of the probe (synchronous or asynchronous) to use.
of_match_table: The open firmware table.
acpi_match_table: The ACPI match table.
probe: Called to query the existence of a specific device, whether this driver can work with it, and bind the driver to a specific device.
remove: Called when the device is removed from the system to unbind a device from this driver.
shutdown: Called at shut-down time to quiesce the device.
suspend: Called to put the device to sleep mode. Usually to a low power state.
resume: Called to bring a device from sleep mode.
groups: Default attributes that get created by the driver core automatically.
pm: Power management operations of the device which matched this driver.
p: Driver core’s private data, no one other than the driver core can touch this.

Description

The device driver-model tracks all of the drivers known to the system. The main reason for this tracking is to enable the driver core to match up drivers with new devices. Once drivers are known objects within the system, however, a number of other things become possible. Device drivers can export information and configuration variables that are independent of any specific device.

struct subsys_interface¶: interfaces to device functions

Definition

struct subsys_interface {
  const char * name;
  struct bus_type * subsys;
  struct list_head node;
  int (* add_dev) (struct device *dev, struct subsys_interface *sif);
  void (* remove_dev) (struct device *dev, struct subsys_interface *sif);
};

Members

name: name of the device function
subsys: subsytem of the devices to attach to
node: the list of functions registered at the subsystem
add_dev: device hookup to device function handler
remove_dev: device hookup to device function handler

Description

Simple interfaces attached to a subsystem. Multiple interfaces can attach to a subsystem and its devices. Unlike drivers, they do not exclusively claim or control devices. Interfaces usually represent a specific functionality of a subsystem/class of devices.

struct class¶: device classes

Definition

struct class {
  const char * name;
  struct module * owner;
  const struct attribute_group ** class_groups;
  const struct attribute_group ** dev_groups;
  struct kobject * dev_kobj;
  int (* dev_uevent) (struct device *dev, struct kobj_uevent_env *env);
  char *(* devnode) (struct device *dev, umode_t *mode);
  void (* class_release) (struct class *class);
  void (* dev_release) (struct device *dev);
  int (* suspend) (struct device *dev, pm_message_t state);
  int (* resume) (struct device *dev);
  int (* shutdown) (struct device *dev);
  const struct kobj_ns_type_operations * ns_type;
  const void *(* namespace) (struct device *dev);
  const struct dev_pm_ops * pm;
  struct subsys_private * p;
};

Members

name: Name of the class.
owner: The module owner.
class_groups: Default attributes of this class.
dev_groups: Default attributes of the devices that belong to the class.
dev_kobj: The kobject that represents this class and links it into the hierarchy.
dev_uevent: Called when a device is added, removed from this class, or a few other things that generate uevents to add the environment variables.
devnode: Callback to provide the devtmpfs.
class_release: Called to release this class.
dev_release: Called to release the device.
suspend: Used to put the device to sleep mode, usually to a low power state.
resume: Used to bring the device from the sleep mode.
shutdown: Called at shut-down time to quiesce the device.
ns_type: Callbacks so sysfs can detemine namespaces.
namespace: Namespace of the device belongs to this class.
pm: The default device power management operations of this class.
p: The private data of the driver core, no one other than the driver core can touch this.

Description

A class is a higher-level view of a device that abstracts out low-level implementation details. Drivers may see a SCSI disk or an ATA disk, but, at the class level, they are all simply disks. Classes allow user space to work with devices based on what they do, rather than how they are connected or how they work.

devm_alloc_percpu(dev, type)¶: Resource-managed alloc_percpu

Parameters

dev: Device to allocate per-cpu memory for
type: Type to allocate per-cpu memory for

Description

Managed alloc_percpu. Per-cpu memory allocated with this function is automatically freed on driver detach.

Return

Pointer to allocated memory on success, NULL on failure.

enum device_link_state¶: Device link states.

Constants

DL_STATE_NONE: The presence of the drivers is not being tracked.
DL_STATE_DORMANT: None of the supplier/consumer drivers is present.
DL_STATE_AVAILABLE: The supplier driver is present, but the consumer is not.
DL_STATE_CONSUMER_PROBE: The consumer is probing (supplier driver present).
DL_STATE_ACTIVE: Both the supplier and consumer drivers are present.
DL_STATE_SUPPLIER_UNBIND: The supplier driver is unbinding.

struct device_link¶: Device link representation.

Definition

struct device_link {
  struct device * supplier;
  struct list_head s_node;
  struct device * consumer;
  struct list_head c_node;
  enum device_link_state status;
  u32 flags;
  bool rpm_active;
#ifdef CONFIG_SRCU
  struct rcu_head rcu_head;
#endif
};

Members

supplier: The device on the supplier end of the link.
s_node: Hook to the supplier device’s list of links to consumers.
consumer: The device on the consumer end of the link.
c_node: Hook to the consumer device’s list of links to suppliers.
status: The state of the link (with respect to the presence of drivers).
flags: Link flags.
rpm_active: Whether or not the consumer device is runtime-PM-active.
rcu_head: An RCU head to use for deferred execution of SRCU callbacks.

enum dl_dev_state¶: Device driver presence tracking information.

Constants

DL_DEV_NO_DRIVER: There is no driver attached to the device.
DL_DEV_PROBING: A driver is probing.
DL_DEV_DRIVER_BOUND: The driver has been bound to the device.
DL_DEV_UNBINDING: The driver is unbinding from the device.

struct dev_links_info¶: Device data related to device links.

Definition

struct dev_links_info {
  struct list_head suppliers;
  struct list_head consumers;
  enum dl_dev_state status;
};

Members

suppliers: List of links to supplier devices.
consumers: List of links to consumer devices.
status: Driver status information.

struct device¶: The basic device structure

Definition

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_links_info links;
  struct dev_pm_info power;
  struct dev_pm_domain * pm_domain;
#ifdef CONFIG_GENERIC_MSI_IRQ_DOMAIN
  struct irq_domain * msi_domain;
#endif
#ifdef CONFIG_PINCTRL
  struct dev_pin_info * pins;
#endif
#ifdef CONFIG_GENERIC_MSI_IRQ
  struct list_head msi_list;
#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 fwnode_handle * fwnode;
  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;
  struct iommu_fwspec * iommu_fwspec;
  bool offline_disabled:1;
  bool offline:1;
  bool of_node_reused: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.
links: Links to suppliers and consumers of this device.
power: For device power management. See Documentation/power/admin-guide/devices.rst 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.
msi_domain: The generic MSI domain this device is using.
pins: For device pin management. See Documentation/pinctrl.txt for details.
msi_list: Hosts MSI descriptors
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_group: IOMMU group the device belongs to.
iommu_fwspec: IOMMU-specific properties supplied by firmware.
offline_disabled: If set, the device is permanently online.
offline: Set after successful invocation of bus type’s .:c:func:offline().
of_node_reused: Set if the device-tree node is shared with an ancestor 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.

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.

module_driver(__driver, __register, __unregister, ...)¶: Helper macro for drivers that don’t do anything special in module init/exit. This eliminates a lot of boilerplate. Each module may only use this macro once, and calling it replaces module_init() and module_exit().

Parameters

__driver: driver name
__register: register function for this driver type
__unregister: unregister function for this driver type
...: Additional arguments to be passed to __register and __unregister.

Description

Use this macro to construct bus specific macros for registering drivers, and do not use it on its own.

builtin_driver(__driver, __register, ...)¶: Helper macro for drivers that don’t do anything special in init and have no exit. This eliminates some boilerplate. Each driver may only use this macro once, and calling it replaces device_initcall (or in some cases, the legacy __initcall). This is meant to be a direct parallel of module_driver() above but without the __exit stuff that is not used for builtin cases.

Parameters

__driver: driver name
__register: register function for this driver type
...: Additional arguments to be passed to __register

Description

Use this macro to construct bus specific macros for registering drivers, and do not use it on its own.

Device Drivers Base¶

void driver_init(void)¶: initialize driver model.

Parameters

void: no arguments

Description

Call the driver model init functions to initialize their subsystems. Called early from init/main.c.

int driver_for_each_device(struct device_driver * drv, struct device * start, void * data, int (*fn) (struct device *, void *)¶: Iterator for devices bound to a driver.

Parameters

struct device_driver * drv: Driver we’re iterating.
struct device * start: Device to begin with
void * data: Data to pass to the callback.
int (*)(struct device *, void *) fn: Function to call for each device.

Description

Iterate over the drv‘s list of devices calling fn for each one.

struct device * driver_find_device(struct device_driver * drv, struct device * start, void * data, int (*match) (struct device *dev, void *data)¶: device iterator for locating a particular device.

Parameters

struct device_driver * drv: The device’s driver
struct device * start: Device to begin with
void * data: Data to pass to match function
int (*)(struct device *dev, void *data) match: Callback function to check device

Description

This is similar to the driver_for_each_device() function above, but it returns a reference to a device that is ‘found’ for later use, as determined by the match callback.

The callback should return 0 if the device doesn’t match and non-zero if it does. If the callback returns non-zero, this function will return to the caller and not iterate over any more devices.

int driver_create_file(struct device_driver * drv, const struct driver_attribute * attr)¶: create sysfs file for driver.

Parameters

struct device_driver * drv: driver.
const struct driver_attribute * attr: driver attribute descriptor.

void driver_remove_file(struct device_driver * drv, const struct driver_attribute * attr)¶: remove sysfs file for driver.

Parameters

struct device_driver * drv: driver.
const struct driver_attribute * attr: driver attribute descriptor.

int driver_register(struct device_driver * drv)¶: register driver with bus

Parameters

struct device_driver * drv: driver to register

Description

We pass off most of the work to the bus_add_driver() call, since most of the things we have to do deal with the bus structures.

void driver_unregister(struct device_driver * drv)¶: remove driver from system.

Parameters

struct device_driver * drv: driver.

Description

Again, we pass off most of the work to the bus-level call.

struct device_driver * driver_find(const char * name, struct bus_type * bus)¶: locate driver on a bus by its name.

Parameters

const char * name: name of the driver.
struct bus_type * bus: bus to scan for the driver.

Description

Call kset_find_obj() to iterate over list of drivers on a bus to find driver by name. Return driver if found.

This routine provides no locking to prevent the driver it returns from being unregistered or unloaded while the caller is using it. The caller is responsible for preventing this.

struct device_link * device_link_add(struct device * consumer, struct device * supplier, u32 flags)¶: Create a link between two devices.

Parameters

struct device * consumer: Consumer end of the link.
struct device * supplier: Supplier end of the link.
u32 flags: Link flags.

Description

The caller is responsible for the proper synchronization of the link creation with runtime PM. First, setting the DL_FLAG_PM_RUNTIME flag will cause the runtime PM framework to take the link into account. Second, if the DL_FLAG_RPM_ACTIVE flag is set in addition to it, the supplier devices will be forced into the active metastate and reference-counted upon the creation of the link. If DL_FLAG_PM_RUNTIME is not set, DL_FLAG_RPM_ACTIVE will be ignored.

If the DL_FLAG_AUTOREMOVE is set, the link will be removed automatically when the consumer device driver unbinds from it. The combination of both DL_FLAG_AUTOREMOVE and DL_FLAG_STATELESS set is invalid and will cause NULL to be returned.

A side effect of the link creation is re-ordering of dpm_list and the devices_kset list by moving the consumer device and all devices depending on it to the ends of these lists (that does not happen to devices that have not been registered when this function is called).

The supplier device is required to be registered when this function is called and NULL will be returned if that is not the case. The consumer device need not be registered, however.

void device_link_del(struct device_link * link)¶: Delete a link between two devices.

Parameters

struct device_link * link: Device link to delete.

Description

The caller must ensure proper synchronization of this function with runtime PM.

const char * dev_driver_string(const struct device * dev)¶: Return a device’s driver name, if at all possible

Parameters

const struct device * dev: struct device to get the name of

Description

Will return the device’s driver’s name if it is bound to a device. If the device is not bound to a driver, it will return the name of the bus it is attached to. If it is not attached to a bus either, an empty string will be returned.

int device_create_file(struct device * dev, const struct device_attribute * attr)¶: create sysfs attribute file for device.

Parameters

struct device * dev: device.
const struct device_attribute * attr: device attribute descriptor.

void device_remove_file(struct device * dev, const struct device_attribute * attr)¶: remove sysfs attribute file.

Parameters

struct device * dev: device.
const struct device_attribute * attr: device attribute descriptor.

bool device_remove_file_self(struct device * dev, const struct device_attribute * attr)¶: remove sysfs attribute file from its own method.

Parameters

struct device * dev: device.
const struct device_attribute * attr: device attribute descriptor.

Description

See kernfs_remove_self() for details.

int device_create_bin_file(struct device * dev, const struct bin_attribute * attr)¶: create sysfs binary attribute file for device.

Parameters

struct device * dev: device.
const struct bin_attribute * attr: device binary attribute descriptor.

void device_remove_bin_file(struct device * dev, const struct bin_attribute * attr)¶: remove sysfs binary attribute file

Parameters

struct device * dev: device.
const struct bin_attribute * attr: device binary attribute descriptor.

void device_initialize(struct device * dev)¶: init device structure.

Parameters

struct device * dev: device.

Description

This prepares the device for use by other layers by initializing its fields. It is the first half of device_register(), if called by that function, though it can also be called separately, so one may use dev‘s fields. In particular, get_device()/put_device() may be used for reference counting of dev after calling this function.

All fields in dev must be initialized by the caller to 0, except for those explicitly set to some other value. The simplest approach is to use kzalloc() to allocate the structure containing dev.

NOTE

Use put_device() to give up your reference instead of freeing dev directly once you have called this function.

int dev_set_name(struct device * dev, const char * fmt, ...)¶: set a device name

Parameters

struct device * dev: device
const char * fmt: format string for the device’s name
...: variable arguments

int device_add(struct device * dev)¶: add device to device hierarchy.

Parameters

struct device * dev: device.

Description

This is part 2 of device_register(), though may be called separately _iff_ device_initialize() has been called separately.

This adds dev to the kobject hierarchy via kobject_add(), adds it to the global and sibling lists for the device, then adds it to the other relevant subsystems of the driver model.

Do not call this routine or device_register() more than once for any device structure. The driver model core is not designed to work with devices that get unregistered and then spring back to life. (Among other things, it’s very hard to guarantee that all references to the previous incarnation of dev have been dropped.) Allocate and register a fresh new struct device instead.

NOTE

_Never_ directly free dev after calling this function, even if it returned an error! Always use put_device() to give up your reference instead.

int device_register(struct device * dev)¶: register a device with the system.

Parameters

struct device * dev: pointer to the device structure

Description

This happens in two clean steps - initialize the device and add it to the system. The two steps can be called separately, but this is the easiest and most common. I.e. you should only call the two helpers separately if have a clearly defined need to use and refcount the device before it is added to the hierarchy.

For more information, see the kerneldoc for device_initialize() and device_add().

NOTE

_Never_ directly free dev after calling this function, even if it returned an error! Always use put_device() to give up the reference initialized in this function instead.

struct device * get_device(struct device * dev)¶: increment reference count for device.

Parameters

struct device * dev: device.

Description

This simply forwards the call to kobject_get(), though we do take care to provide for the case that we get a NULL pointer passed in.

void put_device(struct device * dev)¶: decrement reference count.

Parameters

struct device * dev: device in question.

void device_del(struct device * dev)¶: delete device from system.

Parameters

struct device * dev: device.

Description

This is the first part of the device unregistration sequence. This removes the device from the lists we control from here, has it removed from the other driver model subsystems it was added to in device_add(), and removes it from the kobject hierarchy.

NOTE

this should be called manually _iff_ device_add() was also called manually.

void device_unregister(struct device * dev)¶: unregister device from system.

Parameters

struct device * dev: device going away.

Description

We do this in two parts, like we do device_register(). First, we remove it from all the subsystems with device_del(), then we decrement the reference count via put_device(). If that is the final reference count, the device will be cleaned up via device_release() above. Otherwise, the structure will stick around until the final reference to the device is dropped.

int device_for_each_child(struct device * parent, void * data, int (*fn) (struct device *dev, void *data)¶: device child iterator.

Parameters

struct device * parent: parent struct device.
void * data: data for the callback.
int (*)(struct device *dev, void *data) fn: function to be called for each device.

Description

Iterate over parent‘s child devices, and call fn for each, passing it data.

We check the return of fn each time. If it returns anything other than 0, we break out and return that value.

int device_for_each_child_reverse(struct device * parent, void * data, int (*fn) (struct device *dev, void *data)¶: device child iterator in reversed order.

Parameters

struct device * parent: parent struct device.
void * data: data for the callback.
int (*)(struct device *dev, void *data) fn: function to be called for each device.

Description

Iterate over parent‘s child devices, and call fn for each, passing it data.

We check the return of fn each time. If it returns anything other than 0, we break out and return that value.

struct device * device_find_child(struct device * parent, void * data, int (*match) (struct device *dev, void *data)¶: device iterator for locating a particular device.

Parameters

struct device * parent: parent struct device
void * data: Data to pass to match function
int (*)(struct device *dev, void *data) match: Callback function to check device

Description

This is similar to the device_for_each_child() function above, but it returns a reference to a device that is ‘found’ for later use, as determined by the match callback.

The callback should return 0 if the device doesn’t match and non-zero if it does. If the callback returns non-zero and a reference to the current device can be obtained, this function will return to the caller and not iterate over any more devices.

NOTE

you will need to drop the reference with put_device() after use.

struct device * __root_device_register(const char * name, struct module * owner)¶: allocate and register a root device

Parameters

const char * name: root device name
struct module * owner: owner module of the root device, usually THIS_MODULE

Description

This function allocates a root device and registers it using device_register(). In order to free the returned device, use root_device_unregister().

Root devices are dummy devices which allow other devices to be grouped under /sys/devices. Use this function to allocate a root device and then use it as the parent of any device which should appear under /sys/devices/{name}

The /sys/devices/{name} directory will also contain a ‘module’ symlink which points to the owner directory in sysfs.

Returns struct device pointer on success, or ERR_PTR() on error.

Note

You probably want to use root_device_register().

void root_device_unregister(struct device * dev)¶: unregister and free a root device

Parameters

struct device * dev: device going away

Description

This function unregisters and cleans up a device that was created by root_device_register().

struct device * device_create_vargs(struct class * class, struct device * parent, dev_t devt, void * drvdata, const char * fmt, va_list args)¶: creates a device and registers it with sysfs

Parameters

struct class * class: pointer to the struct class that this device should be registered to
struct device * parent: pointer to the parent struct device of this new device, if any
dev_t devt: the dev_t for the char device to be added
void * drvdata: the data to be added to the device for callbacks
const char * fmt: string for the device’s name
va_list args: va_list for the device’s name

Description

This function can be used by char device classes. A struct device will be created in sysfs, registered to the specified class.

A “dev” file will be created, showing the dev_t for the device, if the dev_t is not 0,0. If a pointer to a parent struct device is passed in, the newly created struct device will be a child of that device in sysfs. The pointer to the struct device will be returned from the call. Any further sysfs files that might be required can be created using this pointer.

Returns struct device pointer on success, or ERR_PTR() on error.

Note

the struct class passed to this function must have previously been created with a call to class_create().

struct device * device_create(struct class * class, struct device * parent, dev_t devt, void * drvdata, const char * fmt, ...)¶: creates a device and registers it with sysfs

Parameters

struct class * class: pointer to the struct class that this device should be registered to
struct device * parent: pointer to the parent struct device of this new device, if any
dev_t devt: the dev_t for the char device to be added
void * drvdata: the data to be added to the device for callbacks
const char * fmt: string for the device’s name
...: variable arguments

Description

This function can be used by char device classes. A struct device will be created in sysfs, registered to the specified class.

A “dev” file will be created, showing the dev_t for the device, if the dev_t is not 0,0. If a pointer to a parent struct device is passed in, the newly created struct device will be a child of that device in sysfs. The pointer to the struct device will be returned from the call. Any further sysfs files that might be required can be created using this pointer.

Returns struct device pointer on success, or ERR_PTR() on error.

Note

the struct class passed to this function must have previously been created with a call to class_create().

struct device * device_create_with_groups(struct class * class, struct device * parent, dev_t devt, void * drvdata, const struct attribute_group ** groups, const char * fmt, ...)¶: creates a device and registers it with sysfs

Parameters

struct class * class: pointer to the struct class that this device should be registered to
struct device * parent: pointer to the parent struct device of this new device, if any
dev_t devt: the dev_t for the char device to be added
void * drvdata: the data to be added to the device for callbacks
const struct attribute_group ** groups: NULL-terminated list of attribute groups to be created
const char * fmt: string for the device’s name
...: variable arguments

Description

This function can be used by char device classes. A struct device will be created in sysfs, registered to the specified class. Additional attributes specified in the groups parameter will also be created automatically.

A “dev” file will be created, showing the dev_t for the device, if the dev_t is not 0,0. If a pointer to a parent struct device is passed in, the newly created struct device will be a child of that device in sysfs. The pointer to the struct device will be returned from the call. Any further sysfs files that might be required can be created using this pointer.

Returns struct device pointer on success, or ERR_PTR() on error.

Note

the struct class passed to this function must have previously been created with a call to class_create().

void device_destroy(struct class * class, dev_t devt)¶: removes a device that was created with device_create()

Parameters

struct class * class: pointer to the struct class that this device was registered with
dev_t devt: the dev_t of the device that was previously registered

Description

This call unregisters and cleans up a device that was created with a call to device_create().

int device_rename(struct device * dev, const char * new_name)¶: renames a device

Parameters

struct device * dev: the pointer to the struct device to be renamed
const char * new_name: the new name of the device

Description

It is the responsibility of the caller to provide mutual exclusion between two different calls of device_rename on the same device to ensure that new_name is valid and won’t conflict with other devices.

Note

Don’t call this function. Currently, the networking layer calls this function, but that will change. The following text from Kay Sievers offers some insight:

Renaming devices is racy at many levels, symlinks and other stuff are not replaced atomically, and you get a “move” uevent, but it’s not easy to connect the event to the old and new device. Device nodes are not renamed at all, there isn’t even support for that in the kernel now.

In the meantime, during renaming, your target name might be taken by another driver, creating conflicts. Or the old name is taken directly after you renamed it – then you get events for the same DEVPATH, before you even see the “move” event. It’s just a mess, and nothing new should ever rely on kernel device renaming. Besides that, it’s not even implemented now for other things than (driver-core wise very simple) network devices.

We are currently about to change network renaming in udev to completely disallow renaming of devices in the same namespace as the kernel uses, because we can’t solve the problems properly, that arise with swapping names of multiple interfaces without races. Means, renaming of eth[0-9]* will only be allowed to some other name than eth[0-9]*, for the aforementioned reasons.

Make up a “real” name in the driver before you register anything, or add some other attributes for userspace to find the device, or use udev to add symlinks – but never rename kernel devices later, it’s a complete mess. We don’t even want to get into that and try to implement the missing pieces in the core. We really have other pieces to fix in the driver core mess. :)

int device_move(struct device * dev, struct device * new_parent, enum dpm_order dpm_order)¶: moves a device to a new parent

Parameters

struct device * dev: the pointer to the struct device to be moved
struct device * new_parent: the new parent of the device (can by NULL)
enum dpm_order dpm_order: how to reorder the dpm_list

void set_primary_fwnode(struct device * dev, struct fwnode_handle * fwnode)¶: Change the primary firmware node of a given device.

Parameters

struct device * dev: Device to handle.
struct fwnode_handle * fwnode: New primary firmware node of the device.

Description

Set the device’s firmware node pointer to fwnode, but if a secondary firmware node of the device is present, preserve it.

void device_set_of_node_from_dev(struct device * dev, const struct device * dev2)¶: reuse device-tree node of another device

Parameters

struct device * dev: device whose device-tree node is being set
const struct device * dev2: device whose device-tree node is being reused

Description

Takes another reference to the new device-tree node after first dropping any reference held to the old node.

void register_syscore_ops(struct syscore_ops * ops)¶: Register a set of system core operations.

Parameters

struct syscore_ops * ops: System core operations to register.

void unregister_syscore_ops(struct syscore_ops * ops)¶: Unregister a set of system core operations.

Parameters

struct syscore_ops * ops: System core operations to unregister.

int syscore_suspend(void)¶: Execute all the registered system core suspend callbacks.

Parameters

void: no arguments

Description

This function is executed with one CPU on-line and disabled interrupts.

void syscore_resume(void)¶: Execute all the registered system core resume callbacks.

Parameters

void: no arguments

Description

This function is executed with one CPU on-line and disabled interrupts.

struct class * __class_create(struct module * owner, const char * name, struct lock_class_key * key)¶: create a struct class structure

Parameters

struct module * owner: pointer to the module that is to “own” this struct class
const char * name: pointer to a string for the name of this class.
struct lock_class_key * key: the lock_class_key for this class; used by mutex lock debugging

Description

This is used to create a struct class pointer that can then be used in calls to device_create().

Returns struct class pointer on success, or ERR_PTR() on error.

Note, the pointer created here is to be destroyed when finished by making a call to class_destroy().

void class_destroy(struct class * cls)¶: destroys a struct class structure

Parameters

struct class * cls: pointer to the struct class that is to be destroyed

Description

Note, the pointer to be destroyed must have been created with a call to class_create().

void class_dev_iter_init(struct class_dev_iter * iter, struct class * class, struct device * start, const struct device_type * type)¶: initialize class device iterator

Parameters

struct class_dev_iter * iter: class iterator to initialize
struct class * class: the class we wanna iterate over
struct device * start: the device to start iterating from, if any
const struct device_type * type: device_type of the devices to iterate over, NULL for all

Description

Initialize class iterator iter such that it iterates over devices of class. If start is set, the list iteration will start there, otherwise if it is NULL, the iteration starts at the beginning of the list.

struct device * class_dev_iter_next(struct class_dev_iter * iter)¶: iterate to the next device

Parameters

struct class_dev_iter * iter: class iterator to proceed

Description

Proceed iter to the next device and return it. Returns NULL if iteration is complete.

The returned device is referenced and won’t be released till iterator is proceed to the next device or exited. The caller is free to do whatever it wants to do with the device including calling back into class code.

void class_dev_iter_exit(struct class_dev_iter * iter)¶: finish iteration

Parameters

struct class_dev_iter * iter: class iterator to finish

Description

Finish an iteration. Always call this function after iteration is complete whether the iteration ran till the end or not.

int class_for_each_device(struct class * class, struct device * start, void * data, int (*fn) (struct device *, void *)¶: device iterator

Parameters

struct class * class: the class we’re iterating
struct device * start: the device to start with in the list, if any.
void * data: data for the callback
int (*)(struct device *, void *) fn: function to be called for each device

Description

Iterate over class‘s list of devices, and call fn for each, passing it data. If start is set, the list iteration will start there, otherwise if it is NULL, the iteration starts at the beginning of the list.

We check the return of fn each time. If it returns anything other than 0, we break out and return that value.

fn is allowed to do anything including calling back into class code. There’s no locking restriction.

struct device * class_find_device(struct class * class, struct device * start, const void * data, int (*match) (struct device *, const void *)¶: device iterator for locating a particular device

Parameters

struct class * class: the class we’re iterating
struct device * start: Device to begin with
const void * data: data for the match function
int (*)(struct device *, const void *) match: function to check device

Description

This is similar to the class_for_each_dev() function above, but it returns a reference to a device that is ‘found’ for later use, as determined by the match callback.

The callback should return 0 if the device doesn’t match and non-zero if it does. If the callback returns non-zero, this function will return to the caller and not iterate over any more devices.

Note, you will need to drop the reference with put_device() after use.

match is allowed to do anything including calling back into class code. There’s no locking restriction.

struct class_compat * class_compat_register(const char * name)¶: register a compatibility class

Parameters

const char * name: the name of the class

Description

Compatibility class are meant as a temporary user-space compatibility workaround when converting a family of class devices to a bus devices.

void class_compat_unregister(struct class_compat * cls)¶: unregister a compatibility class

Parameters

struct class_compat * cls: the class to unregister

int class_compat_create_link(struct class_compat * cls, struct device * dev, struct device * device_link)¶: create a compatibility class device link to a bus device

Parameters

struct class_compat * cls: the compatibility class
struct device * dev: the target bus device
struct device * device_link: an optional device to which a “device” link should be created

void class_compat_remove_link(struct class_compat * cls, struct device * dev, struct device * device_link)¶: remove a compatibility class device link to a bus device

Parameters

struct class_compat * cls: the compatibility class
struct device * dev: the target bus device
struct device * device_link: an optional device to which a “device” link was previously created

void unregister_node(struct node * node)¶: unregister a node device

Parameters

struct node * node: node going away

Description

Unregisters a node device node. All the devices on the node must be unregistered before calling this function.

int request_firmware(const struct firmware ** firmware_p, const char * name, struct device * device)¶: send firmware request and wait for it

Parameters

const struct firmware ** firmware_p: pointer to firmware image
const char * name: name of firmware file
struct device * device: device for which firmware is being loaded

Description

firmware_p will be used to return a firmware image by the name of name for device device.

Should be called from user context where sleeping is allowed.

name will be used as $FIRMWARE in the uevent environment and should be distinctive enough not to be confused with any other firmware image for this or any other device.

Caller must hold the reference count of device.

The function can be called safely inside device’s suspend and resume callback.

int request_firmware_direct(const struct firmware ** firmware_p, const char * name, struct device * device)¶: load firmware directly without usermode helper

Parameters

const struct firmware ** firmware_p: pointer to firmware image
const char * name: name of firmware file
struct device * device: device for which firmware is being loaded

Description

This function works pretty much like request_firmware(), but this doesn’t fall back to usermode helper even if the firmware couldn’t be loaded directly from fs. Hence it’s useful for loading optional firmwares, which aren’t always present, without extra long timeouts of udev.

int request_firmware_into_buf(const struct firmware ** firmware_p, const char * name, struct device * device, void * buf, size_t size)¶: load firmware into a previously allocated buffer

Parameters

const struct firmware ** firmware_p: pointer to firmware image
const char * name: name of firmware file
struct device * device: device for which firmware is being loaded and DMA region allocated
void * buf: address of buffer to load firmware into
size_t size: size of buffer

Description

This function works pretty much like request_firmware(), but it doesn’t allocate a buffer to hold the firmware data. Instead, the firmware is loaded directly into the buffer pointed to by buf and the firmware_p data member is pointed at buf.

This function doesn’t cache firmware either.

void release_firmware(const struct firmware * fw)¶: release the resource associated with a firmware image

Parameters

const struct firmware * fw: firmware resource to release

int request_firmware_nowait(struct module * module, bool uevent, const char * name, struct device * device, gfp_t gfp, void * context, void (*cont) (const struct firmware *fw, void *context)¶: asynchronous version of request_firmware

Parameters

struct module * module: module requesting the firmware
bool uevent: sends uevent to copy the firmware image if this flag is non-zero else the firmware copy must be done manually.
const char * name: name of firmware file
struct device * device: device for which firmware is being loaded
gfp_t gfp: allocation flags
void * context: will be passed over to cont, and fw may be NULL if firmware request fails.
void (*)(const struct firmware *fw, void *context) cont: function will be called asynchronously when the firmware request is over.

Description

Caller must hold the reference count of device.

Asynchronous variant of request_firmware() for user contexts:

sleep for as small periods as possible since it may increase kernel boot time of built-in device drivers requesting firmware in their ->:c:func:probe() methods, if gfp is GFP_KERNEL.

can’t sleep at all if gfp is GFP_ATOMIC.

int transport_class_register(struct transport_class * tclass)¶: register an initial transport class

Parameters

struct transport_class * tclass: a pointer to the transport class structure to be initialised

Description

The transport class contains an embedded class which is used to identify it. The caller should initialise this structure with zeros and then generic class must have been initialised with the actual transport class unique name. There’s a macro DECLARE_TRANSPORT_CLASS() to do this (declared classes still must be registered).

Returns 0 on success or error on failure.

void transport_class_unregister(struct transport_class * tclass)¶: unregister a previously registered class

Parameters

struct transport_class * tclass: The transport class to unregister

Description

Must be called prior to deallocating the memory for the transport class.

int anon_transport_class_register(struct anon_transport_class * atc)¶: register an anonymous class

Parameters

struct anon_transport_class * atc: The anon transport class to register

Description

The anonymous transport class contains both a transport class and a container. The idea of an anonymous class is that it never actually has any device attributes associated with it (and thus saves on container storage). So it can only be used for triggering events. Use prezero and then use DECLARE_ANON_TRANSPORT_CLASS() to initialise the anon transport class storage.

void anon_transport_class_unregister(struct anon_transport_class * atc)¶: unregister an anon class

Parameters

struct anon_transport_class * atc: Pointer to the anon transport class to unregister

Description

Must be called prior to deallocating the memory for the anon transport class.

void transport_setup_device(struct device * dev)¶: declare a new dev for transport class association but don’t make it visible yet.

Parameters

struct device * dev: the generic device representing the entity being added

Description

Usually, dev represents some component in the HBA system (either the HBA itself or a device remote across the HBA bus). This routine is simply a trigger point to see if any set of transport classes wishes to associate with the added device. This allocates storage for the class device and initialises it, but does not yet add it to the system or add attributes to it (you do this with transport_add_device). If you have no need for a separate setup and add operations, use transport_register_device (see transport_class.h).

void transport_add_device(struct device * dev)¶: declare a new dev for transport class association

Parameters

struct device * dev: the generic device representing the entity being added

Description

Usually, dev represents some component in the HBA system (either the HBA itself or a device remote across the HBA bus). This routine is simply a trigger point used to add the device to the system and register attributes for it.

void transport_configure_device(struct device * dev)¶: configure an already set up device

Parameters

struct device * dev: generic device representing device to be configured

Description

The idea of configure is simply to provide a point within the setup process to allow the transport class to extract information from a device after it has been setup. This is used in SCSI because we have to have a setup device to begin using the HBA, but after we send the initial inquiry, we use configure to extract the device parameters. The device need not have been added to be configured.

void transport_remove_device(struct device * dev)¶: remove the visibility of a device

Parameters

struct device * dev: generic device to remove

Description

This call removes the visibility of the device (to the user from sysfs), but does not destroy it. To eliminate a device entirely you must also call transport_destroy_device. If you don’t need to do remove and destroy as separate operations, use transport_unregister_device() (see transport_class.h) which will perform both calls for you.

void transport_destroy_device(struct device * dev)¶: destroy a removed device

Parameters

struct device * dev: device to eliminate from the transport class.

Description

This call triggers the elimination of storage associated with the transport classdev. Note: all it really does is relinquish a reference to the classdev. The memory will not be freed until the last reference goes to zero. Note also that the classdev retains a reference count on dev, so dev too will remain for as long as the transport class device remains around.

int device_bind_driver(struct device * dev)¶: bind a driver to one device.

Parameters

struct device * dev: device.

Description

Allow manual attachment of a driver to a device. Caller must have already set dev->driver.

Note that this does not modify the bus reference count nor take the bus’s rwsem. Please verify those are accounted for before calling this. (It is ok to call with no other effort from a driver’s probe() method.)

This function must be called with the device lock held.

void wait_for_device_probe(void)¶

Parameters

void: no arguments

Description

Wait for device probing to be completed.

int device_attach(struct device * dev)¶: try to attach device to a driver.

Parameters

struct device * dev: device.

Description

Walk the list of drivers that the bus has and call driver_probe_device() for each pair. If a compatible pair is found, break out and return.

Returns 1 if the device was bound to a driver; 0 if no matching driver was found; -ENODEV if the device is not registered.

When called for a USB interface, dev->parent lock must be held.

int driver_attach(struct device_driver * drv)¶: try to bind driver to devices.

Parameters

struct device_driver * drv: driver.

Description

Walk the list of devices that the bus has on it and try to match the driver with each one. If driver_probe_device() returns 0 and the dev->driver is set, we’ve found a compatible pair.

void device_release_driver(struct device * dev)¶: manually detach device from driver.

Parameters

struct device * dev: device.

Description

Manually detach device from driver. When called for a USB interface, dev->parent lock must be held.

If this function is to be called with dev->parent lock held, ensure that the device’s consumers are unbound in advance or that their locks can be acquired under the dev->parent lock.

struct platform_device * platform_device_register_resndata(struct device * parent, const char * name, int id, const struct resource * res, unsigned int num, const void * data, size_t size)¶: add a platform-level device with resources and platform-specific data

Parameters

struct device * parent: parent device for the device we’re adding
const char * name: base name of the device we’re adding
int id: instance id
const struct resource * res: set of resources that needs to be allocated for the device
unsigned int num: number of resources
const void * data: platform specific data for this platform device
size_t size: size of platform specific data

Description

Returns struct platform_device pointer on success, or ERR_PTR() on error.

struct platform_device * platform_device_register_simple(const char * name, int id, const struct resource * res, unsigned int num)¶: add a platform-level device and its resources

Parameters

const char * name: base name of the device we’re adding
int id: instance id
const struct resource * res: set of resources that needs to be allocated for the device
unsigned int num: number of resources

Description

This function creates a simple platform device that requires minimal resource and memory management. Canned release function freeing memory allocated for the device allows drivers using such devices to be unloaded without waiting for the last reference to the device to be dropped.

This interface is primarily intended for use with legacy drivers which probe hardware directly. Because such drivers create sysfs device nodes themselves, rather than letting system infrastructure handle such device enumeration tasks, they don’t fully conform to the Linux driver model. In particular, when such drivers are built as modules, they can’t be “hotplugged”.

Returns struct platform_device pointer on success, or ERR_PTR() on error.

struct platform_device * platform_device_register_data(struct device * parent, const char * name, int id, const void * data, size_t size)¶: add a platform-level device with platform-specific data

Parameters

struct device * parent: parent device for the device we’re adding
const char * name: base name of the device we’re adding
int id: instance id
const void * data: platform specific data for this platform device
size_t size: size of platform specific data

Description

This function creates a simple platform device that requires minimal resource and memory management. Canned release function freeing memory allocated for the device allows drivers using such devices to be unloaded without waiting for the last reference to the device to be dropped.

Returns struct platform_device pointer on success, or ERR_PTR() on error.

struct resource * platform_get_resource(struct platform_device * dev, unsigned int type, unsigned int num)¶: get a resource for a device

Parameters

struct platform_device * dev: platform device
unsigned int type: resource type
unsigned int num: resource index

int platform_get_irq(struct platform_device * dev, unsigned int num)¶: get an IRQ for a device

Parameters

struct platform_device * dev: platform device
unsigned int num: IRQ number index

int platform_irq_count(struct platform_device * dev)¶: Count the number of IRQs a platform device uses

Parameters

struct platform_device * dev: platform device

Return

Number of IRQs a platform device uses or EPROBE_DEFER

struct resource * platform_get_resource_byname(struct platform_device * dev, unsigned int type, const char * name)¶: get a resource for a device by name

Parameters

struct platform_device * dev: platform device
unsigned int type: resource type
const char * name: resource name

int platform_get_irq_byname(struct platform_device * dev, const char * name)¶: get an IRQ for a device by name

Parameters

struct platform_device * dev: platform device
const char * name: IRQ name

int platform_add_devices(struct platform_device ** devs, int num)¶: add a numbers of platform devices

Parameters

struct platform_device ** devs: array of platform devices to add
int num: number of platform devices in array

void platform_device_put(struct platform_device * pdev)¶: destroy a platform device

Parameters

struct platform_device * pdev: platform device to free

Description

Free all memory associated with a platform device. This function must _only_ be externally called in error cases. All other usage is a bug.

struct platform_device * platform_device_alloc(const char * name, int id)¶: create a platform device

Parameters

const char * name: base name of the device we’re adding
int id: instance id

Description

Create a platform device object which can have other objects attached to it, and which will have attached objects freed when it is released.

int platform_device_add_resources(struct platform_device * pdev, const struct resource * res, unsigned int num)¶: add resources to a platform device

Parameters

struct platform_device * pdev: platform device allocated by platform_device_alloc to add resources to
const struct resource * res: set of resources that needs to be allocated for the device
unsigned int num: number of resources

Description

Add a copy of the resources to the platform device. The memory associated with the resources will be freed when the platform device is released.

int platform_device_add_data(struct platform_device * pdev, const void * data, size_t size)¶: add platform-specific data to a platform device

Parameters

struct platform_device * pdev: platform device allocated by platform_device_alloc to add resources to
const void * data: platform specific data for this platform device
size_t size: size of platform specific data

Description

Add a copy of platform specific data to the platform device’s platform_data pointer. The memory associated with the platform data will be freed when the platform device is released.

int platform_device_add_properties(struct platform_device * pdev, const struct property_entry * properties)¶: add built-in properties to a platform device

Parameters

struct platform_device * pdev: platform device to add properties to
const struct property_entry * properties: null terminated array of properties to add

Description

The function will take deep copy of properties and attach the copy to the platform device. The memory associated with properties will be freed when the platform device is released.

int platform_device_add(struct platform_device * pdev)¶: add a platform device to device hierarchy

Parameters

struct platform_device * pdev: platform device we’re adding

Description

This is part 2 of platform_device_register(), though may be called separately _iff_ pdev was allocated by platform_device_alloc().

void platform_device_del(struct platform_device * pdev)¶: remove a platform-level device

Parameters

struct platform_device * pdev: platform device we’re removing

Description

Note that this function will also release all memory- and port-based resources owned by the device (dev->resource). This function must _only_ be externally called in error cases. All other usage is a bug.

int platform_device_register(struct platform_device * pdev)¶: add a platform-level device

Parameters

struct platform_device * pdev: platform device we’re adding

void platform_device_unregister(struct platform_device * pdev)¶: unregister a platform-level device

Parameters

struct platform_device * pdev: platform device we’re unregistering

Description

Unregistration is done in 2 steps. First we release all resources and remove it from the subsystem, then we drop reference count by calling platform_device_put().

struct platform_device * platform_device_register_full(const struct platform_device_info * pdevinfo)¶: add a platform-level device with resources and platform-specific data

Parameters

const struct platform_device_info * pdevinfo: data used to create device

Description

Returns struct platform_device pointer on success, or ERR_PTR() on error.

int __platform_driver_register(struct platform_driver * drv, struct module * owner)¶: register a driver for platform-level devices

Parameters

struct platform_driver * drv: platform driver structure
struct module * owner: owning module/driver

void platform_driver_unregister(struct platform_driver * drv)¶: unregister a driver for platform-level devices

Parameters

struct platform_driver * drv: platform driver structure

int __platform_driver_probe(struct platform_driver * drv, int (*probe) (struct platform_device *, struct module * module)¶: register driver for non-hotpluggable device

Parameters

struct platform_driver * drv: platform driver structure
int (*)(struct platform_device *) probe: the driver probe routine, probably from an __init section
struct module * module: module which will be the owner of the driver

Description

Use this instead of platform_driver_register() when you know the device is not hotpluggable and has already been registered, and you want to remove its run-once probe() infrastructure from memory after the driver has bound to the device.

One typical use for this would be with drivers for controllers integrated into system-on-chip processors, where the controller devices have been configured as part of board setup.

Note that this is incompatible with deferred probing.

Returns zero if the driver registered and bound to a device, else returns a negative error code and with the driver not registered.

struct platform_device * __platform_create_bundle(struct platform_driver * driver, int (*probe) (struct platform_device *, struct resource * res, unsigned int n_res, const void * data, size_t size, struct module * module)¶: register driver and create corresponding device

Parameters

struct platform_driver * driver: platform driver structure
int (*)(struct platform_device *) probe: the driver probe routine, probably from an __init section
struct resource * res: set of resources that needs to be allocated for the device
unsigned int n_res: number of resources
const void * data: platform specific data for this platform device
size_t size: size of platform specific data
struct module * module: module which will be the owner of the driver

Description

Use this in legacy-style modules that probe hardware directly and register a single platform device and corresponding platform driver.

Returns struct platform_device pointer on success, or ERR_PTR() on error.

int __platform_register_drivers(struct platform_driver *const * drivers, unsigned int count, struct module * owner)¶: register an array of platform drivers

Parameters

struct platform_driver *const * drivers: an array of drivers to register
unsigned int count: the number of drivers to register
struct module * owner: module owning the drivers

Description

Registers platform drivers specified by an array. On failure to register a driver, all previously registered drivers will be unregistered. Callers of this API should use platform_unregister_drivers() to unregister drivers in the reverse order.

Return

0 on success or a negative error code on failure.

void platform_unregister_drivers(struct platform_driver *const * drivers, unsigned int count)¶: unregister an array of platform drivers

Parameters

struct platform_driver *const * drivers: an array of drivers to unregister
unsigned int count: the number of drivers to unregister

Description

Unegisters platform drivers specified by an array. This is typically used to complement an earlier call to platform_register_drivers(). Drivers are unregistered in the reverse order in which they were registered.

int bus_for_each_dev(struct bus_type * bus, struct device * start, void * data, int (*fn) (struct device *, void *)¶: device iterator.

Parameters

struct bus_type * bus: bus type.
struct device * start: device to start iterating from.
void * data: data for the callback.
int (*)(struct device *, void *) fn: function to be called for each device.

Description

Iterate over bus‘s list of devices, and call fn for each, passing it data. If start is not NULL, we use that device to begin iterating from.

We check the return of fn each time. If it returns anything other than 0, we break out and return that value.

NOTE

The device that returns a non-zero value is not retained in any way, nor is its refcount incremented. If the caller needs to retain this data, it should do so, and increment the reference count in the supplied callback.

struct device * bus_find_device(struct bus_type * bus, struct device * start, void * data, int (*match) (struct device *dev, void *data)¶: device iterator for locating a particular device.

Parameters

struct bus_type * bus: bus type
struct device * start: Device to begin with
void * data: Data to pass to match function
int (*)(struct device *dev, void *data) match: Callback function to check device

Description

This is similar to the bus_for_each_dev() function above, but it returns a reference to a device that is ‘found’ for later use, as determined by the match callback.

The callback should return 0 if the device doesn’t match and non-zero if it does. If the callback returns non-zero, this function will return to the caller and not iterate over any more devices.

struct device * bus_find_device_by_name(struct bus_type * bus, struct device * start, const char * name)¶: device iterator for locating a particular device of a specific name

Parameters

struct bus_type * bus: bus type
struct device * start: Device to begin with
const char * name: name of the device to match

Description

This is similar to the bus_find_device() function above, but it handles searching by a name automatically, no need to write another strcmp matching function.

struct device * subsys_find_device_by_id(struct bus_type * subsys, unsigned int id, struct device * hint)¶: find a device with a specific enumeration number

Parameters

struct bus_type * subsys: subsystem
unsigned int id: index ‘id’ in struct device
struct device * hint: device to check first

Description

Check the hint’s next object and if it is a match return it directly, otherwise, fall back to a full list search. Either way a reference for the returned object is taken.

int bus_for_each_drv(struct bus_type * bus, struct device_driver * start, void * data, int (*fn) (struct device_driver *, void *)¶: driver iterator

Parameters

struct bus_type * bus: bus we’re dealing with.
struct device_driver * start: driver to start iterating on.
void * data: data to pass to the callback.
int (*)(struct device_driver *, void *) fn: function to call for each driver.

Description

This is nearly identical to the device iterator above. We iterate over each driver that belongs to bus, and call fn for each. If fn returns anything but 0, we break out and return it. If start is not NULL, we use it as the head of the list.

NOTE

we don’t return the driver that returns a non-zero value, nor do we leave the reference count incremented for that driver. If the caller needs to know that info, it must set it in the callback. It must also be sure to increment the refcount so it doesn’t disappear before returning to the caller.

int bus_rescan_devices(struct bus_type * bus)¶: rescan devices on the bus for possible drivers

Parameters

struct bus_type * bus: the bus to scan.

Description

This function will look for devices on the bus with no driver attached and rescan it against existing drivers to see if it matches any by calling device_attach() for the unbound devices.

int device_reprobe(struct device * dev)¶: remove driver for a device and probe for a new driver

Parameters

struct device * dev: the device to reprobe

Description

This function detaches the attached driver (if any) for the given device and restarts the driver probing process. It is intended to use if probing criteria changed during a devices lifetime and driver attachment should change accordingly.

int bus_register(struct bus_type * bus)¶: register a driver-core subsystem

Parameters

struct bus_type * bus: bus to register

Description

Once we have that, we register the bus with the kobject infrastructure, then register the children subsystems it has: the devices and drivers that belong to the subsystem.

void bus_unregister(struct bus_type * bus)¶: remove a bus from the system

Parameters

struct bus_type * bus: bus.

Description

Unregister the child subsystems and the bus itself. Finally, we call bus_put() to release the refcount

void subsys_dev_iter_init(struct subsys_dev_iter * iter, struct bus_type * subsys, struct device * start, const struct device_type * type)¶: initialize subsys device iterator

Parameters

struct subsys_dev_iter * iter: subsys iterator to initialize
struct bus_type * subsys: the subsys we wanna iterate over
struct device * start: the device to start iterating from, if any
const struct device_type * type: device_type of the devices to iterate over, NULL for all

Description

Initialize subsys iterator iter such that it iterates over devices of subsys. If start is set, the list iteration will start there, otherwise if it is NULL, the iteration starts at the beginning of the list.

struct device * subsys_dev_iter_next(struct subsys_dev_iter * iter)¶: iterate to the next device

Parameters

struct subsys_dev_iter * iter: subsys iterator to proceed

Description

Proceed iter to the next device and return it. Returns NULL if iteration is complete.

The returned device is referenced and won’t be released till iterator is proceed to the next device or exited. The caller is free to do whatever it wants to do with the device including calling back into subsys code.

void subsys_dev_iter_exit(struct subsys_dev_iter * iter)¶: finish iteration

Parameters

struct subsys_dev_iter * iter: subsys iterator to finish

Description

Finish an iteration. Always call this function after iteration is complete whether the iteration ran till the end or not.

int subsys_system_register(struct bus_type * subsys, const struct attribute_group ** groups)¶: register a subsystem at /sys/devices/system/

Parameters

struct bus_type * subsys: system subsystem
const struct attribute_group ** groups: default attributes for the root device

Description

All ‘system’ subsystems have a /sys/devices/system/<name> root device with the name of the subsystem. The root device can carry subsystem- wide attributes. All registered devices are below this single root device and are named after the subsystem with a simple enumeration number appended. The registered devices are not explicitly named; only ‘id’ in the device needs to be set.

Do not use this interface for anything new, it exists for compatibility with bad ideas only. New subsystems should use plain subsystems; and add the subsystem-wide attributes should be added to the subsystem directory itself and not some create fake root-device placed in /sys/devices/system/<name>.

int subsys_virtual_register(struct bus_type * subsys, const struct attribute_group ** groups)¶: register a subsystem at /sys/devices/virtual/

Parameters

struct bus_type * subsys: virtual subsystem
const struct attribute_group ** groups: default attributes for the root device

Description

All ‘virtual’ subsystems have a /sys/devices/system/<name> root device with the name of the subystem. The root device can carry subsystem-wide attributes. All registered devices are below this single root device. There’s no restriction on device naming. This is for kernel software constructs which need sysfs interface.

Device Drivers DMA Management¶

int dma_alloc_from_dev_coherent(struct device * dev, ssize_t size, dma_addr_t * dma_handle, void ** ret)¶: allocate memory from device coherent pool

Parameters

struct device * dev: device from which we allocate memory
ssize_t size: size of requested memory area
dma_addr_t * dma_handle: This will be filled with the correct dma handle
void ** ret: This pointer will be filled with the virtual address to allocated area.

Description

This function should be only called from per-arch dma_alloc_coherent() to support allocation from per-device coherent memory pools.

Returns 0 if dma_alloc_coherent should continue with allocating from generic memory areas, or !0 if dma_alloc_coherent should return ret.

int dma_release_from_dev_coherent(struct device * dev, int order, void * vaddr)¶: free memory to device coherent memory pool

Parameters

struct device * dev: device from which the memory was allocated
int order: the order of pages allocated
void * vaddr: virtual address of allocated pages

Description

This checks whether the memory was allocated from the per-device coherent memory pool and if so, releases that memory.

Returns 1 if we correctly released the memory, or 0 if the caller should proceed with releasing memory from generic pools.

int dma_mmap_from_dev_coherent(struct device * dev, struct vm_area_struct * vma, void * vaddr, size_t size, int * ret)¶: mmap memory from the device coherent pool

Parameters

struct device * dev: device from which the memory was allocated
struct vm_area_struct * vma: vm_area for the userspace memory
void * vaddr: cpu address returned by dma_alloc_from_dev_coherent
size_t size: size of the memory buffer allocated
int * ret: result from remap_pfn_range()

Description

This checks whether the memory was allocated from the per-device coherent memory pool and if so, maps that memory to the provided vma.

Returns 1 if we correctly mapped the memory, or 0 if the caller should proceed with mapping memory from generic pools.

void * dmam_alloc_coherent(struct device * dev, size_t size, dma_addr_t * dma_handle, gfp_t gfp)¶: Managed dma_alloc_coherent()

Parameters

struct device * dev: Device to allocate coherent memory for
size_t size: Size of allocation
dma_addr_t * dma_handle: Out argument for allocated DMA handle
gfp_t gfp: Allocation flags

Description

Managed dma_alloc_coherent(). Memory allocated using this function will be automatically released on driver detach.

Return

Pointer to allocated memory on success, NULL on failure.

void dmam_free_coherent(struct device * dev, size_t size, void * vaddr, dma_addr_t dma_handle)¶: Managed dma_free_coherent()

Parameters

struct device * dev: Device to free coherent memory for
size_t size: Size of allocation
void * vaddr: Virtual address of the memory to free
dma_addr_t dma_handle: DMA handle of the memory to free

Description

Managed dma_free_coherent().

void * dmam_alloc_attrs(struct device * dev, size_t size, dma_addr_t * dma_handle, gfp_t gfp, unsigned long attrs)¶: Managed dma_alloc_attrs()

Parameters

struct device * dev: Device to allocate non_coherent memory for
size_t size: Size of allocation
dma_addr_t * dma_handle: Out argument for allocated DMA handle
gfp_t gfp: Allocation flags
unsigned long attrs: Flags in the DMA_ATTR_* namespace.

Description

Managed dma_alloc_attrs(). Memory allocated using this function will be automatically released on driver detach.

Return

Pointer to allocated memory on success, NULL on failure.

int dmam_declare_coherent_memory(struct device * dev, phys_addr_t phys_addr, dma_addr_t device_addr, size_t size, int flags)¶: Managed dma_declare_coherent_memory()

Parameters

struct device * dev: Device to declare coherent memory for
phys_addr_t phys_addr: Physical address of coherent memory to be declared
dma_addr_t device_addr: Device address of coherent memory to be declared
size_t size: Size of coherent memory to be declared
int flags: Flags

Description

Managed dma_declare_coherent_memory().

Return

0 on success, -errno on failure.

void dmam_release_declared_memory(struct device * dev)¶: Managed dma_release_declared_memory().

Parameters

struct device * dev: Device to release declared coherent memory for

Description

Managed dmam_release_declared_memory().

Device drivers PnP support¶

int pnp_register_protocol(struct pnp_protocol * protocol)¶: adds a pnp protocol to the pnp layer

Parameters

struct pnp_protocol * protocol: pointer to the corresponding pnp_protocol structure

Description

Ex protocols: ISAPNP, PNPBIOS, etc

void pnp_unregister_protocol(struct pnp_protocol * protocol)¶: removes a pnp protocol from the pnp layer

Parameters

struct pnp_protocol * protocol: pointer to the corresponding pnp_protocol structure

struct pnp_dev * pnp_request_card_device(struct pnp_card_link * clink, const char * id, struct pnp_dev * from)¶: Searches for a PnP device under the specified card

Parameters

struct pnp_card_link * clink: pointer to the card link, cannot be NULL
const char * id: pointer to a PnP ID structure that explains the rules for finding the device
struct pnp_dev * from: Starting place to search from. If NULL it will start from the beginning.

void pnp_release_card_device(struct pnp_dev * dev)¶: call this when the driver no longer needs the device

Parameters

struct pnp_dev * dev: pointer to the PnP device structure

int pnp_register_card_driver(struct pnp_card_driver * drv)¶: registers a PnP card driver with the PnP Layer

Parameters

struct pnp_card_driver * drv: pointer to the driver to register

void pnp_unregister_card_driver(struct pnp_card_driver * drv)¶: unregisters a PnP card driver from the PnP Layer

Parameters

struct pnp_card_driver * drv: pointer to the driver to unregister

struct pnp_id * pnp_add_id(struct pnp_dev * dev, const char * id)¶: adds an EISA id to the specified device

Parameters

struct pnp_dev * dev: pointer to the desired device
const char * id: pointer to an EISA id string

int pnp_start_dev(struct pnp_dev * dev)¶: low-level start of the PnP device

Parameters

struct pnp_dev * dev: pointer to the desired device

Description

assumes that resources have already been allocated

int pnp_stop_dev(struct pnp_dev * dev)¶: low-level disable of the PnP device

Parameters

struct pnp_dev * dev: pointer to the desired device

Description

does not free resources

int pnp_activate_dev(struct pnp_dev * dev)¶: activates a PnP device for use

Parameters

struct pnp_dev * dev: pointer to the desired device

Description

does not validate or set resources so be careful.

int pnp_disable_dev(struct pnp_dev * dev)¶: disables device

Parameters

struct pnp_dev * dev: pointer to the desired device

Description

inform the correct pnp protocol so that resources can be used by other devices

int pnp_is_active(struct pnp_dev * dev)¶: Determines if a device is active based on its current resources

Parameters

struct pnp_dev * dev: pointer to the desired PnP device

Userspace IO devices¶

void uio_event_notify(struct uio_info * info)¶: trigger an interrupt event

Parameters

struct uio_info * info: UIO device capabilities

int __uio_register_device(struct module * owner, struct device * parent, struct uio_info * info)¶: register a new userspace IO device

Parameters

struct module * owner: module that creates the new device
struct device * parent: parent device
struct uio_info * info: UIO device capabilities

Description

returns zero on success or a negative error code.

void uio_unregister_device(struct uio_info * info)¶: unregister a industrial IO device

Parameters

struct uio_info * info: UIO device capabilities

struct uio_mem¶: description of a UIO memory region

Definition

struct uio_mem {
  const char * name;
  phys_addr_t addr;
  unsigned long offs;
  resource_size_t size;
  int memtype;
  void __iomem * internal_addr;
  struct uio_map * map;
};

Members

name: name of the memory region for identification
addr: address of the device’s memory rounded to page size (phys_addr is used since addr can be logical, virtual, or physical & phys_addr_t should always be large enough to handle any of the address types)
offs: offset of device memory within the page
size: size of IO (multiple of page size)
memtype: type of memory addr points to
internal_addr: ioremap-ped version of addr, for driver internal use
map: for use by the UIO core only.

struct uio_port¶: description of a UIO port region

Definition

struct uio_port {
  const char * name;
  unsigned long start;
  unsigned long size;
  int porttype;
  struct uio_portio * portio;
};

Members

name: name of the port region for identification
start: start of port region
size: size of port region
porttype: type of port (see UIO_PORT_* below)
portio: for use by the UIO core only.

struct uio_info¶: UIO device capabilities

Definition

struct uio_info {
  struct uio_device * uio_dev;
  const char * name;
  const char * version;
  struct uio_mem mem;
  struct uio_port port;
  long irq;
  unsigned long irq_flags;
  void * priv;
  irqreturn_t (* handler) (int irq, struct uio_info *dev_info);
  int (* mmap) (struct uio_info *info, struct vm_area_struct *vma);
  int (* open) (struct uio_info *info, struct inode *inode);
  int (* release) (struct uio_info *info, struct inode *inode);
  int (* irqcontrol) (struct uio_info *info, s32 irq_on);
};

Members

uio_dev: the UIO device this info belongs to
name: device name
version: device driver version
mem: list of mappable memory regions, size==0 for end of list
port: list of port regions, size==0 for end of list
irq: interrupt number or UIO_IRQ_CUSTOM
irq_flags: flags for request_irq()
priv: optional private data
handler: the device’s irq handler
mmap: mmap operation for this uio device
open: open operation for this uio device
release: release operation for this uio device
irqcontrol: disable/enable irqs when 0/1 is written to /dev/uioX