Device drivers infrastructure¶

The Basic Device Driver-Model Structures¶

struct subsys_interface¶: interfaces to device functions

Definition:

struct subsys_interface {
    const char *name;
    const 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: subsystem 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 device_attribute¶: Interface for exporting device attributes.

Definition:

struct device_attribute {
    struct attribute        attr;
    ssize_t (*show)(struct device *dev, struct device_attribute *attr, char *buf);
    ssize_t (*store)(struct device *dev, struct device_attribute *attr, const char *buf, size_t count);
};

Members

attr: sysfs attribute definition.
show: Show handler.
store: Store handler.

struct dev_ext_attribute¶: Exported device attribute with extra context.

Definition:

struct dev_ext_attribute {
    struct device_attribute attr;
    void *var;
};

Members

attr: Exported device attribute.
var: Pointer to context.

DEVICE_ATTR¶

DEVICE_ATTR (_name, _mode, _show, _store)

Define a device attribute.

Parameters

_name: Attribute name.
_mode: File mode.
_show: Show handler. Optional, but mandatory if attribute is readable.
_store: Store handler. Optional, but mandatory if attribute is writable.

Description

Convenience macro for defining a struct device_attribute.

For example, DEVICE_ATTR(foo, 0644, foo_show, foo_store); expands to:

struct device_attribute dev_attr_foo = {
        .attr   = { .name = "foo", .mode = 0644 },
        .show   = foo_show,
        .store  = foo_store,
};

DEVICE_ATTR_PREALLOC¶

DEVICE_ATTR_PREALLOC (_name, _mode, _show, _store)

Define a preallocated device attribute.

Parameters

_name: Attribute name.
_mode: File mode.
_show: Show handler. Optional, but mandatory if attribute is readable.
_store: Store handler. Optional, but mandatory if attribute is writable.

Description

Like DEVICE_ATTR(), but SYSFS_PREALLOC is set on _mode.

DEVICE_ATTR_RW¶

DEVICE_ATTR_RW (_name)

Define a read-write device attribute.

Parameters

_name: Attribute name.

Description

Like DEVICE_ATTR(), but _mode is 0644, _show is <_name>_show, and _store is <_name>_store.

DEVICE_ATTR_ADMIN_RW¶

DEVICE_ATTR_ADMIN_RW (_name)

Define an admin-only read-write device attribute.

Parameters

_name: Attribute name.

Description

Like DEVICE_ATTR_RW(), but _mode is 0600.

DEVICE_ATTR_RO¶

DEVICE_ATTR_RO (_name)

Define a readable device attribute.

Parameters

_name: Attribute name.

Description

Like DEVICE_ATTR(), but _mode is 0444 and _show is <_name>_show.

DEVICE_ATTR_ADMIN_RO¶

DEVICE_ATTR_ADMIN_RO (_name)

Define an admin-only readable device attribute.

Parameters

_name: Attribute name.

Description

Like DEVICE_ATTR_RO(), but _mode is 0400.

DEVICE_ATTR_WO¶

DEVICE_ATTR_WO (_name)

Define an admin-only writable device attribute.

Parameters

_name: Attribute name.

Description

Like DEVICE_ATTR(), but _mode is 0200 and _store is <_name>_store.

DEVICE_ULONG_ATTR¶

DEVICE_ULONG_ATTR (_name, _mode, _var)

Define a device attribute backed by an unsigned long.

Parameters

_name: Attribute name.
_mode: File mode.
_var: Identifier of unsigned long.

Description

Like DEVICE_ATTR(), but _show and _store are automatically provided such that reads and writes to the attribute from userspace affect _var.

DEVICE_INT_ATTR¶

DEVICE_INT_ATTR (_name, _mode, _var)

Define a device attribute backed by an int.

Parameters

_name: Attribute name.
_mode: File mode.
_var: Identifier of int.

Description

Like DEVICE_ULONG_ATTR(), but _var is an int.

DEVICE_BOOL_ATTR¶

DEVICE_BOOL_ATTR (_name, _mode, _var)

Define a device attribute backed by a bool.

Parameters

_name: Attribute name.
_mode: File mode.
_var: Identifier of bool.

Description

Like DEVICE_ULONG_ATTR(), but _var is a bool.

DEVICE_STRING_ATTR_RO¶

DEVICE_STRING_ATTR_RO (_name, _mode, _var)

Define a device attribute backed by a r/o string.

Parameters

_name: Attribute name.
_mode: File mode.
_var: Identifier of string.

Description

Like DEVICE_ULONG_ATTR(), but _var is a string. Because the length of the string allocation is unknown, the attribute must be read-only.

devm_alloc_percpu¶

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 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.

enum device_removable¶: Whether the device is removable. The criteria for a device to be classified as removable is determined by its subsystem or bus.

Constants

DEVICE_REMOVABLE_NOT_SUPPORTED: This attribute is not supported for this device (default).
DEVICE_REMOVABLE_UNKNOWN: Device location is Unknown.
DEVICE_FIXED: Device is not removable by the user.
DEVICE_REMOVABLE: Device is removable by the user.

struct dev_links_info¶: Device data related to device links.

Definition:

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

Members

suppliers: List of links to supplier devices.
consumers: List of links to consumer devices.
defer_sync: Hook to global list of devices that have deferred sync_state.
status: Driver status information.

struct dev_msi_info¶: Device data related to MSI

Definition:

struct dev_msi_info {
#ifdef CONFIG_GENERIC_MSI_IRQ;
    struct irq_domain       *domain;
    struct msi_device_data  *data;
#endif;
};

Members

domain: The MSI interrupt domain associated to the device
data: Pointer to MSI device data

enum device_physical_location_panel¶: Describes which panel surface of the system’s housing the device connection point resides on.

Constants

DEVICE_PANEL_TOP: Device connection point is on the top panel.
DEVICE_PANEL_BOTTOM: Device connection point is on the bottom panel.
DEVICE_PANEL_LEFT: Device connection point is on the left panel.
DEVICE_PANEL_RIGHT: Device connection point is on the right panel.
DEVICE_PANEL_FRONT: Device connection point is on the front panel.
DEVICE_PANEL_BACK: Device connection point is on the back panel.
DEVICE_PANEL_UNKNOWN: The panel with device connection point is unknown.

enum device_physical_location_vertical_position¶: Describes vertical position of the device connection point on the panel surface.

Constants

DEVICE_VERT_POS_UPPER: Device connection point is at upper part of panel.
DEVICE_VERT_POS_CENTER: Device connection point is at center part of panel.
DEVICE_VERT_POS_LOWER: Device connection point is at lower part of panel.

enum device_physical_location_horizontal_position¶: Describes horizontal position of the device connection point on the panel surface.

Constants

DEVICE_HORI_POS_LEFT: Device connection point is at left part of panel.
DEVICE_HORI_POS_CENTER: Device connection point is at center part of panel.
DEVICE_HORI_POS_RIGHT: Device connection point is at right part of panel.

struct device_physical_location¶: Device data related to physical location of the device connection point.

Definition:

struct device_physical_location {
    enum device_physical_location_panel panel;
    enum device_physical_location_vertical_position vertical_position;
    enum device_physical_location_horizontal_position horizontal_position;
    bool dock;
    bool lid;
};

Members

panel: Panel surface of the system’s housing that the device connection point resides on.
vertical_position: Vertical position of the device connection point within the panel.
horizontal_position: Horizontal position of the device connection point within the panel.
dock: Set if the device connection point resides in a docking station or port replicator.
lid: Set if this device connection point resides on the lid of laptop system.

struct device¶: The basic device structure

Definition:

struct device {
    struct kobject kobj;
    struct device           *parent;
    struct device_private   *p;
    const char              *init_name;
    const struct device_type *type;
    const struct bus_type   *bus;
    struct device_driver *driver;
    void *platform_data;
    void *driver_data;
    struct mutex            mutex;
    struct dev_links_info   links;
    struct dev_pm_info      power;
    struct dev_pm_domain    *pm_domain;
#ifdef CONFIG_ENERGY_MODEL;
    struct em_perf_domain   *em_pd;
#endif;
#ifdef CONFIG_PINCTRL;
    struct dev_pin_info     *pins;
#endif;
    struct dev_msi_info     msi;
#ifdef CONFIG_DMA_OPS;
    const struct dma_map_ops *dma_ops;
#endif;
    u64 *dma_mask;
    u64 coherent_dma_mask;
    u64 bus_dma_limit;
    const struct bus_dma_region *dma_range_map;
    struct device_dma_parameters *dma_parms;
    struct list_head        dma_pools;
#ifdef CONFIG_DMA_DECLARE_COHERENT;
    struct dma_coherent_mem *dma_mem;
#endif;
#ifdef CONFIG_DMA_CMA;
    struct cma *cma_area;
#endif;
#ifdef CONFIG_SWIOTLB;
    struct io_tlb_mem *dma_io_tlb_mem;
#endif;
#ifdef CONFIG_SWIOTLB_DYNAMIC;
    struct list_head dma_io_tlb_pools;
    spinlock_t dma_io_tlb_lock;
    bool dma_uses_io_tlb;
#endif;
    struct dev_archdata     archdata;
    struct device_node      *of_node;
    struct fwnode_handle    *fwnode;
#ifdef CONFIG_NUMA;
    int numa_node;
#endif;
    dev_t devt;
    u32 id;
    spinlock_t devres_lock;
    struct list_head        devres_head;
    const struct class      *class;
    const struct attribute_group **groups;
    void (*release)(struct device *dev);
    struct iommu_group      *iommu_group;
    struct dev_iommu        *iommu;
    struct device_physical_location *physical_location;
    enum device_removable   removable;
    bool offline_disabled:1;
    bool offline:1;
    bool of_node_reused:1;
    bool state_synced:1;
    bool can_match:1;
#if defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_DEVICE) ||     defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU) ||     defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU_ALL);
    bool dma_coherent:1;
#endif;
#ifdef CONFIG_DMA_OPS_BYPASS;
    bool dma_ops_bypass : 1;
#endif;
#ifdef CONFIG_DMA_NEED_SYNC;
    bool dma_skip_sync:1;
#endif;
};

Members

kobj: A top-level, abstract class from which other classes are derived.
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.
init_name: Initial name of the device.
type: The type of device. This identifies the device type and carries type-specific information.
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.
mutex: Mutex to synchronize calls to its driver.
links: Links to suppliers and consumers of this device.
power: For device power management. See Device Power Management Basics 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.
em_pd: device’s energy model performance domain
pins: For device pin management. See PINCTRL (PIN CONTROL) subsystem for details.
msi: MSI related data
dma_ops: DMA mapping operations for this device.
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.
bus_dma_limit: Limit of an upstream bridge or bus which imposes a smaller DMA limit than the device itself supports.
dma_range_map: map for DMA memory ranges relative to that 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
dma_io_tlb_mem: Software IO TLB allocator. Not for driver use.
dma_io_tlb_pools: List of transient swiotlb memory pools.
dma_io_tlb_lock: Protects changes to the list of active pools.
dma_uses_io_tlb: true if device has used the software IO TLB.
archdata: For arch-specific additions.
of_node: Associated device tree node.
fwnode: Associated device node supplied by platform firmware.
numa_node: NUMA node this device is close to.
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.
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: Per device generic IOMMU runtime data
physical_location: Describes physical location of the device connection point in the system housing.
removable: Whether the device can be removed from the system. This should be set by the subsystem / bus driver that discovered the device.
offline_disabled: If set, the device is permanently online.
offline: Set after successful invocation of bus type’s .offline().
of_node_reused: Set if the device-tree node is shared with an ancestor device.
state_synced: The hardware state of this device has been synced to match the software state of this device by calling the driver/bus sync_state() callback.
can_match: The device has matched with a driver at least once or it is in a bus (like AMBA) which can’t check for matching drivers until other devices probe successfully.
dma_coherent: this particular device is dma coherent, even if the architecture supports non-coherent devices.
dma_ops_bypass: If set to true then the dma_ops are bypassed for the streaming DMA operations (->map_* / ->unmap_* / ->sync_*), and optionall (if the coherent mask is large enough) also for dma allocations. This flag is managed by the dma ops instance from ->dma_supported.
dma_skip_sync: DMA sync operations can be skipped for coherent buffers.

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.

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;
    struct device link_dev;
    enum device_link_state status;
    u32 flags;
    refcount_t rpm_active;
    struct kref kref;
    struct work_struct rm_work;
    bool supplier_preactivated;
};

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.
link_dev: device used to expose link details in sysfs
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.
kref: Count repeated addition of the same link.
rm_work: Work structure used for removing the link.
supplier_preactivated: Supplier has been made active before consumer probe.

bool device_iommu_mapped(struct device *dev)¶: Returns true when the device DMA is translated by an IOMMU

Parameters

struct device *dev: Device to perform the check on

const char *dev_name(const struct device *dev)¶: Return a device’s name.

Parameters

const struct device *dev: Device with name to get.

Return

The kobject name of the device, or its initial name if unavailable.

const char *dev_bus_name(const struct device *dev)¶: Return a device’s bus/class name, if at all possible

Parameters

const struct device *dev: struct device to get the bus/class name of

Description

Will return the name of the bus/class the device is attached to. If it is not attached to a bus/class, an empty string will be returned.

device_lock_set_class¶

device_lock_set_class (dev, key)

Specify a temporary lock class while a device is attached to a driver

Parameters

dev: device to modify
key: lock class key data

Description

This must be called with the device_lock() already held, for example from driver ->probe(). Take care to only override the default lockdep_no_validate class.

device_lock_reset_class¶

device_lock_reset_class (dev)

Return a device to the default lockdep novalidate state

Parameters

dev: device to modify

Description

This must be called with the device_lock() already held, for example from driver ->remove().

struct bus_type¶: The bus type of the device

Definition:

struct bus_type {
    const char              *name;
    const char              *dev_name;
    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)(const struct device *dev, struct kobj_uevent_env *env);
    int (*probe)(struct device *dev);
    void (*sync_state)(struct device *dev);
    void (*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);
    int (*dma_configure)(struct device *dev);
    void (*dma_cleanup)(struct device *dev);
    const struct dev_pm_ops *pm;
    bool need_parent_lock;
};

Members

name: The name of the bus.
dev_name: Used for subsystems to enumerate devices like (“foo``u``”, dev->id).
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.
sync_state: Called to sync device state to software state after all the state tracking consumers linked to this device (present at the time of late_initcall) have successfully bound to a driver. If the device has no consumers, this function will be called at late_initcall_sync level. If the device has consumers that are never bound to a driver, this function will never get called until they do.
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.
dma_configure: Called to setup DMA configuration on a device on this bus.
dma_cleanup: Called to cleanup DMA configuration on a device on this bus.
pm: Power management operations of this bus, callback the specific device driver’s pm-ops.
need_parent_lock: When probing or removing a device on this bus, the device core should lock the device’s parent.

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 bus_notifier_event¶: Bus Notifier events that have happened

Constants

BUS_NOTIFY_ADD_DEVICE: device is added to this bus
BUS_NOTIFY_DEL_DEVICE: device is about to be removed from this bus
BUS_NOTIFY_REMOVED_DEVICE: device is successfully removed from this bus
BUS_NOTIFY_BIND_DRIVER: a driver is about to be bound to this device on this bus
BUS_NOTIFY_BOUND_DRIVER: a driver is successfully bound to this device on this bus
BUS_NOTIFY_UNBIND_DRIVER: a driver is about to be unbound from this device on this bus
BUS_NOTIFY_UNBOUND_DRIVER: a driver is successfully unbound from this device on this bus
BUS_NOTIFY_DRIVER_NOT_BOUND: a driver failed to be bound to this device on this bus

Description

These are the value passed to a bus notifier when a specific event happens.

Note that bus notifiers are likely to be called with the device lock already held by the driver core, so be careful in any notifier callback as to what you do with the device structure.

All bus notifiers are called with the target struct device * as an argument.

struct class¶: device classes

Definition:

struct class {
    const char              *name;
    const struct attribute_group    **class_groups;
    const struct attribute_group    **dev_groups;
    int (*dev_uevent)(const struct device *dev, struct kobj_uevent_env *env);
    char *(*devnode)(const struct device *dev, umode_t *mode);
    void (*class_release)(const struct class *class);
    void (*dev_release)(struct device *dev);
    int (*shutdown_pre)(struct device *dev);
    const struct kobj_ns_type_operations *ns_type;
    const void *(*namespace)(const struct device *dev);
    void (*get_ownership)(const struct device *dev, kuid_t *uid, kgid_t *gid);
    const struct dev_pm_ops *pm;
};

Members

name: Name of the class.
class_groups: Default attributes of this class.
dev_groups: Default attributes of the devices that belong to the class.
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.
shutdown_pre: Called at shut-down time before driver shutdown.
ns_type: Callbacks so sysfs can detemine namespaces.
namespace: Namespace of the device belongs to this class.
get_ownership: Allows class to specify uid/gid of the sysfs directories for the devices belonging to the class. Usually tied to device’s namespace.
pm: The default device power management operations of this class.

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.

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;
    const 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);
    void (*sync_state)(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 attribute_group **dev_groups;
    const struct dev_pm_ops *pm;
    void (*coredump) (struct device *dev);
    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.
sync_state: Called to sync device state to software state after all the state tracking consumers linked to this device (present at the time of late_initcall) have successfully bound to a driver. If the device has no consumers, this function will be called at late_initcall_sync level. If the device has consumers that are never bound to a driver, this function will never get called until they do.
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.
dev_groups: Additional attributes attached to device instance once it is bound to the driver.
pm: Power management operations of the device which matched this driver.
coredump: Called when sysfs entry is written to. The device driver is expected to call the dev_coredump API resulting in a uevent.
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.

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.

struct device *driver_find_device_by_name(struct device_driver *drv, const char *name)¶: device iterator for locating a particular device of a specific name.

Parameters

struct device_driver *drv: the driver we’re iterating
const char *name: name of the device to match

struct device *driver_find_device_by_of_node(struct device_driver *drv, const struct device_node *np)¶: device iterator for locating a particular device by of_node pointer.

Parameters

struct device_driver *drv: the driver we’re iterating
const struct device_node *np: of_node pointer to match.

struct device *driver_find_device_by_fwnode(struct device_driver *drv, const struct fwnode_handle *fwnode)¶: device iterator for locating a particular device by fwnode pointer.

Parameters

struct device_driver *drv: the driver we’re iterating
const struct fwnode_handle *fwnode: fwnode pointer to match.

struct device *driver_find_device_by_devt(struct device_driver *drv, dev_t devt)¶: device iterator for locating a particular device by devt.

Parameters

struct device_driver *drv: the driver we’re iterating
dev_t devt: devt pointer to match.

struct device *driver_find_device_by_acpi_dev(struct device_driver *drv, const struct acpi_device *adev)¶: device iterator for locating a particular device matching the ACPI_COMPANION device.

Parameters

struct device_driver *drv: the driver we’re iterating
const struct acpi_device *adev: ACPI_COMPANION device to match.

module_driver¶

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¶

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.

int driver_set_override(struct device *dev, const char **override, const char *s, size_t len)¶: Helper to set or clear driver override.

Parameters

struct device *dev: Device to change
const char **override: Address of string to change (e.g. device->driver_override); The contents will be freed and hold newly allocated override.
const char *s: NUL-terminated string, new driver name to force a match, pass empty string to clear it (”” or “n”, where the latter is only for sysfs interface).
size_t len: length of s

Description

Helper to set or clear driver override in a device, intended for the cases when the driver_override field is allocated by driver/bus code.

Return

0 on success or a negative error code on failure.

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 (*fn)(struct device *, void *): 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, const void *data, int (*match)(struct device *dev, const 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
const void *data: Data to pass to match function
int (*match)(struct device *dev, const void *data): 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.

void device_link_wait_removal(void)¶: Wait for ongoing devlink removal jobs to terminate

Parameters

void: no arguments

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 meta state 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 DL_FLAG_STATELESS is set in flags, the caller of this function is expected to release the link returned by it directly with the help of either device_link_del() or device_link_remove().

If that flag is not set, however, the caller of this function is handing the management of the link over to the driver core entirely and its return value can only be used to check whether or not the link is present. In that case, the DL_FLAG_AUTOREMOVE_CONSUMER and DL_FLAG_AUTOREMOVE_SUPPLIER device link flags can be used to indicate to the driver core when the link can be safely deleted. Namely, setting one of them in flags indicates to the driver core that the link is not going to be used (by the given caller of this function) after unbinding the consumer or supplier driver, respectively, from its device, so the link can be deleted at that point. If none of them is set, the link will be maintained until one of the devices pointed to by it (either the consumer or the supplier) is unregistered.

Also, if DL_FLAG_STATELESS, DL_FLAG_AUTOREMOVE_CONSUMER and DL_FLAG_AUTOREMOVE_SUPPLIER are not set in flags (that is, a persistent managed device link is being added), the DL_FLAG_AUTOPROBE_CONSUMER flag can be used to request the driver core to automatically probe for a consumer driver after successfully binding a driver to the supplier device.

The combination of DL_FLAG_STATELESS and one of DL_FLAG_AUTOREMOVE_CONSUMER, DL_FLAG_AUTOREMOVE_SUPPLIER, or DL_FLAG_AUTOPROBE_CONSUMER set in flags at the same time is invalid and will cause NULL to be returned upfront. However, if a device link between the given consumer and supplier pair exists already when this function is called for them, the existing link will be returned regardless of its current type and status (the link’s flags may be modified then). The caller of this function is then expected to treat the link as though it has just been created, so (in particular) if DL_FLAG_STATELESS was passed in flags, the link needs to be released explicitly when not needed any more (as stated above).

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 stateless 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. If the link was added multiple times, it needs to be deleted as often. Care is required for hotplugged devices: Their links are purged on removal and calling device_link_del() is then no longer allowed.

void device_link_remove(void *consumer, struct device *supplier)¶: Delete a stateless link between two devices.

Parameters

void *consumer: Consumer end of the link.
struct device *supplier: Supplier end of the link.

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 devm_device_add_group(struct device *dev, const struct attribute_group *grp)¶: given a device, create a managed attribute group

Parameters

struct device *dev: The device to create the group for
const struct attribute_group *grp: The attribute group to create

Description

This function creates a group for the first time. It will explicitly warn and error if any of the attribute files being created already exist.

Returns 0 on success or error code on failure.

int devm_device_add_groups(struct device *dev, const struct attribute_group **groups)¶: create a bunch of managed attribute groups

Parameters

struct device *dev: The device to create the group for
const struct attribute_group **groups: The attribute groups to create, NULL terminated

Description

This function creates a bunch of managed attribute groups. If an error occurs when creating a group, all previously created groups will be removed, unwinding everything back to the original state when this function was called. It will explicitly warn and error if any of the attribute files being created already exist.

Returns 0 on success or error code from sysfs_create_group on failure.

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.

Rule of thumb is: if device_add() succeeds, you should call device_del() when you want to get rid of it. If device_add() has not succeeded, use only put_device() to drop the reference count.

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 (*fn)(struct device *dev, void *data): 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 (*fn)(struct device *dev, void *data): 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 (*match)(struct device *dev, void *data): 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 *device_find_child_by_name(struct device *parent, const char *name)¶: device iterator for locating a child device.

Parameters

struct device *parent: parent struct device
const char *name: name of the child device

Description

This is similar to the device_find_child() function above, but it returns a reference to a device that has the name name.

NOTE

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

struct device *device_find_any_child(struct device *parent)¶: device iterator for locating a child device, if any.

Parameters

struct device *parent: parent struct device

Description

This is similar to the device_find_child() function above, but it returns a reference to a child device, if any.

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

Parameters

const 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.

struct device *device_create_with_groups(const 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

const 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.

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

Parameters

const 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.

However, if you’re writing new code, do not call this function. 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.

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. :)

Note

given that some subsystems (networking and infiniband) use this function, with no immediate plans for this to change, we cannot assume or require that this function not be called at all.

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 be NULL)
enum dpm_order dpm_order: how to reorder the dpm_list

int device_change_owner(struct device *dev, kuid_t kuid, kgid_t kgid)¶: change the owner of an existing device.

Parameters

struct device *dev: device.
kuid_t kuid: new owner’s kuid
kgid_t kgid: new owner’s kgid

Description

This changes the owner of dev and its corresponding sysfs entries to kuid/kgid. This function closely mirrors how dev was added via driver core.

Returns 0 on success or error code on failure.

int dev_err_probe(const struct device *dev, int err, const char *fmt, ...)¶: probe error check and log helper

Parameters

const struct device *dev: the pointer to the struct device
int err: error value to test
const char *fmt: printf-style format string
...: arguments as specified in the format string

Description

This helper implements common pattern present in probe functions for error checking: print debug or error message depending if the error value is -EPROBE_DEFER and propagate error upwards. In case of -EPROBE_DEFER it sets also defer probe reason, which can be checked later by reading devices_deferred debugfs attribute. It replaces code sequence:

if (err != -EPROBE_DEFER)
        dev_err(dev, ...);
else
        dev_dbg(dev, ...);
return err;

with:

return dev_err_probe(dev, err, ...);

Using this helper in your probe function is totally fine even if err is known to never be -EPROBE_DEFER. The benefit compared to a normal dev_err() is the standardized format of the error code, it being emitted symbolically (i.e. you get “EAGAIN” instead of “-35”) and the fact that the error code is returned which allows more compact error paths.

Returns err.

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.

Valid fwnode cases are:

primary --> secondary --> -ENODEV
primary --> NULL
secondary --> -ENODEV
NULL

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

Parameters

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

Description

If a primary firmware node of the device is present, set its secondary pointer to fwnode. Otherwise, set the device’s firmware node pointer to fwnode.

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 device *class_find_device_by_name(const struct class *class, const char *name)¶: device iterator for locating a particular device of a specific name.

Parameters

const struct class *class: class type
const char *name: name of the device to match

struct device *class_find_device_by_of_node(const struct class *class, const struct device_node *np)¶: device iterator for locating a particular device matching the of_node.

Parameters

const struct class *class: class type
const struct device_node *np: of_node of the device to match.

struct device *class_find_device_by_fwnode(const struct class *class, const struct fwnode_handle *fwnode)¶: device iterator for locating a particular device matching the fwnode.

Parameters

const struct class *class: class type
const struct fwnode_handle *fwnode: fwnode of the device to match.

struct device *class_find_device_by_devt(const struct class *class, dev_t devt)¶: device iterator for locating a particular device matching the device type.

Parameters

const struct class *class: class type
dev_t devt: device type of the device to match.

struct device *class_find_device_by_acpi_dev(const struct class *class, const struct acpi_device *adev)¶: device iterator for locating a particular device matching the ACPI_COMPANION device.

Parameters

const struct class *class: class type
const struct acpi_device *adev: ACPI_COMPANION device to match.

struct class *class_create(const char *name)¶: create a struct class structure

Parameters

const char *name: pointer to a string for the name of this class.

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(const struct class *cls)¶: destroys a struct class structure

Parameters

const 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, const struct class *class, const struct device *start, const struct device_type *type)¶: initialize class device iterator

Parameters

struct class_dev_iter *iter: class iterator to initialize
const struct class *class: the class we wanna iterate over
const 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(const struct class *class, const struct device *start, void *data, int (*fn)(struct device*, void*))¶: device iterator

Parameters

const struct class *class: the class we’re iterating
const struct device *start: the device to start with in the list, if any.
void *data: data for the callback
int (*fn)(struct device *, void *): 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(const struct class *class, const struct device *start, const void *data, int (*match)(struct device*, const void*))¶: device iterator for locating a particular device

Parameters

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

bool class_is_registered(const struct class *class)¶: determine if at this moment in time, a class is registered in the driver core or not.

Parameters

const struct class *class: the class to check

Description

Returns a boolean to state if the class is registered in the driver core or not. Note that the value could switch right after this call is made, so only use this in places where you “know” it is safe to do so (usually to determine if the specific class has been registered yet or not).

Be careful in using this.

struct node_access_nodes¶: Access class device to hold user visible relationships to other nodes.

Definition:

struct node_access_nodes {
    struct device           dev;
    struct list_head        list_node;
    unsigned int            access;
#ifdef CONFIG_HMEM_REPORTING;
    struct access_coordinate        coord;
#endif;
};

Members

dev: Device for this memory access class
list_node: List element in the node’s access list
access: The access class rank
coord: Heterogeneous memory performance coordinates

struct node_cache_info¶: Internal tracking for memory node caches

Definition:

struct node_cache_info {
    struct device dev;
    struct list_head node;
    struct node_cache_attrs cache_attrs;
};

Members

dev: Device represeting the cache level
node: List element for tracking in the node
cache_attrs: Attributes for this cache level

void node_add_cache(unsigned int nid, struct node_cache_attrs *cache_attrs)¶: add cache attribute to a memory node

Parameters

unsigned int nid: Node identifier that has new cache attributes
struct node_cache_attrs *cache_attrs: Attributes for the cache being added

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 register_memory_node_under_compute_node(unsigned int mem_nid, unsigned int cpu_nid, enum access_coordinate_class access)¶: link memory node to its compute node for a given access class.

Parameters

unsigned int mem_nid: Memory node number
unsigned int cpu_nid: Cpu node number
enum access_coordinate_class access: Access class to register

Description

For use with platforms that may have separate memory and compute nodes. This function will export node relationships linking which memory initiator nodes can access memory targets at a given ranked access class.

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).

int 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 driver_deferred_probe_check_state(struct device *dev)¶: Check deferred probe state

Parameters

struct device *dev: device to check

Return

-ENODEV if initcalls have completed and modules are disabled.
-ETIMEDOUT if the deferred probe timeout was set and has expired and modules are enabled.
-EPROBE_DEFER in other cases.

Description

Drivers or subsystems can opt-in to calling this function instead of directly returning -EPROBE_DEFER.

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. Please verify that is 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.

Callers should prefer to use device_driver_attach() instead.

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 device_driver_attach(struct device_driver *drv, struct device *dev)¶: attach a specific driver to a specific device

Parameters

struct device_driver *drv: Driver to attach
struct device *dev: Device to attach it to

Description

Manually attach driver to a device. Will acquire both dev lock and dev->parent lock if needed. Returns 0 on success, -ERR on failure.

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

Return

a pointer to the resource or NULL on failure.

void __iomem *devm_platform_get_and_ioremap_resource(struct platform_device *pdev, unsigned int index, struct resource **res)¶: call devm_ioremap_resource() for a platform device and get resource

Parameters

struct platform_device *pdev: platform device to use both for memory resource lookup as well as resource management
unsigned int index: resource index
struct resource **res: optional output parameter to store a pointer to the obtained resource.

Return

a pointer to the remapped memory or an ERR_PTR() encoded error code on failure.

void __iomem *devm_platform_ioremap_resource(struct platform_device *pdev, unsigned int index)¶: call devm_ioremap_resource() for a platform device

Parameters

struct platform_device *pdev: platform device to use both for memory resource lookup as well as resource management
unsigned int index: resource index

Return

a pointer to the remapped memory or an ERR_PTR() encoded error code on failure.

void __iomem *devm_platform_ioremap_resource_byname(struct platform_device *pdev, const char *name)¶: call devm_ioremap_resource for a platform device, retrieve the resource by name

Parameters

struct platform_device *pdev: platform device to use both for memory resource lookup as well as resource management
const char *name: name of the resource

Return

a pointer to the remapped memory or an ERR_PTR() encoded error code on failure.

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

Parameters

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

Description

Gets an IRQ for a platform device. Device drivers should check the return value for errors so as to not pass a negative integer value to the request_irq() APIs. This is the same as platform_get_irq(), except that it does not print an error message if an IRQ can not be obtained.

For example:

int irq = platform_get_irq_optional(pdev, 0);
if (irq < 0)
        return irq;

Return

non-zero IRQ number on success, negative error number on failure.

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

Description

Gets an IRQ for a platform device and prints an error message if finding the IRQ fails. Device drivers should check the return value for errors so as to not pass a negative integer value to the request_irq() APIs.

For example:

int irq = platform_get_irq(pdev, 0);
if (irq < 0)
        return irq;

Return

non-zero IRQ number on success, negative error number on failure.

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

int devm_platform_get_irqs_affinity(struct platform_device *dev, struct irq_affinity *affd, unsigned int minvec, unsigned int maxvec, int **irqs)¶: devm method to get a set of IRQs for a device using an interrupt affinity descriptor

Parameters

struct platform_device *dev: platform device pointer
struct irq_affinity *affd: affinity descriptor
unsigned int minvec: minimum count of interrupt vectors
unsigned int maxvec: maximum count of interrupt vectors
int **irqs: pointer holder for IRQ numbers

Description

Gets a set of IRQs for a platform device, and updates IRQ afffinty according to the passed affinity descriptor

Return

Number of vectors on success, negative error number on failure.

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

Description

Get an IRQ like platform_get_irq(), but then by name rather then by index.

Return

non-zero IRQ number on success, negative error number on failure.

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

Parameters

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

Description

Get an optional IRQ by name like platform_get_irq_byname(). Except that it does not print an error message if an IRQ can not be obtained.

Return

non-zero IRQ number on success, negative error number on failure.

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

Return

0 on success, negative error number on failure.

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(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

NOTE

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

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 (*probe)(struct platform_device *): 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 (*probe)(struct platform_device *): 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

Unregisters 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.

struct device *platform_find_device_by_driver(struct device *start, const struct device_driver *drv)¶: Find a platform device with a given driver.

Parameters

struct device *start: The device to start the search from.
const struct device_driver *drv: The device driver to look for.

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

Parameters

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

struct device *bus_find_device_by_of_node(const struct bus_type *bus, const struct device_node *np)¶: device iterator for locating a particular device matching the of_node.

Parameters

const struct bus_type *bus: bus type
const struct device_node *np: of_node of the device to match.

struct device *bus_find_device_by_fwnode(const struct bus_type *bus, const struct fwnode_handle *fwnode)¶: device iterator for locating a particular device matching the fwnode.

Parameters

const struct bus_type *bus: bus type
const struct fwnode_handle *fwnode: fwnode of the device to match.

struct device *bus_find_device_by_devt(const struct bus_type *bus, dev_t devt)¶: device iterator for locating a particular device matching the device type.

Parameters

const struct bus_type *bus: bus type
dev_t devt: device type of the device to match.

struct device *bus_find_next_device(const struct bus_type *bus, struct device *cur)¶: Find the next device after a given device in a given bus.

Parameters

const struct bus_type *bus: bus type
struct device *cur: device to begin the search with.

struct device *bus_find_device_by_acpi_dev(const struct bus_type *bus, const struct acpi_device *adev)¶: device iterator for locating a particular device matching the ACPI COMPANION device.

Parameters

const struct bus_type *bus: bus type
const struct acpi_device *adev: ACPI COMPANION device to match.

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

Parameters

const struct bus_type *bus: bus type.
struct device *start: device to start iterating from.
void *data: data for the callback.
int (*fn)(struct device *, void *): 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(const struct bus_type *bus, struct device *start, const void *data, int (*match)(struct device *dev, const void *data))¶: device iterator for locating a particular device.

Parameters

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

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

Parameters

const 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 (*fn)(struct device_driver *, void *): 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(const struct bus_type *bus)¶: rescan devices on the bus for possible drivers

Parameters

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

Parameters

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

Parameters

const struct bus_type *bus: bus.

Description

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

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

Parameters

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

Parameters

const 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.

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

Parameters

const char *name: name of the driver.
const 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 *bus_get_dev_root(const struct bus_type *bus)¶: return a pointer to the “device root” of a bus

Parameters

const struct bus_type *bus: bus to return the device root of.

Description

If a bus has a “device root” structure, return it, WITH THE REFERENCE COUNT INCREMENTED.

Note, when finished with the device, a call to put_device() is required.

If the device root is not present (or bus is not a valid pointer), NULL will be returned.

Device Drivers DMA Management¶

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.

unsigned int dma_map_sg_attrs(struct device *dev, struct scatterlist *sg, int nents, enum dma_data_direction dir, unsigned long attrs)¶: Map the given buffer for DMA

Parameters

struct device *dev: The device for which to perform the DMA operation
struct scatterlist *sg: The sg_table object describing the buffer
int nents: Number of entries to map
enum dma_data_direction dir: DMA direction
unsigned long attrs: Optional DMA attributes for the map operation

Description

Maps a buffer described by a scatterlist passed in the sg argument with nents segments for the dir DMA operation by the dev device.

Returns the number of mapped entries (which can be less than nents) on success. Zero is returned for any error.

dma_unmap_sg_attrs() should be used to unmap the buffer with the original sg and original nents (not the value returned by this funciton).

int dma_map_sgtable(struct device *dev, struct sg_table *sgt, enum dma_data_direction dir, unsigned long attrs)¶: Map the given buffer for DMA

Parameters

struct device *dev: The device for which to perform the DMA operation
struct sg_table *sgt: The sg_table object describing the buffer
enum dma_data_direction dir: DMA direction
unsigned long attrs: Optional DMA attributes for the map operation

Description

Maps a buffer described by a scatterlist stored in the given sg_table object for the dir DMA operation by the dev device. After success, the ownership for the buffer is transferred to the DMA domain. One has to call dma_sync_sgtable_for_cpu() or dma_unmap_sgtable() to move the ownership of the buffer back to the CPU domain before touching the buffer by the CPU.

Returns 0 on success or a negative error code on error. The following error codes are supported with the given meaning:

-EINVAL

An invalid argument, unaligned access or other error in usage. Will not succeed if retried.

-ENOMEM

Insufficient resources (like memory or IOVA space) to complete the mapping. Should succeed if retried later.

-EIO

Legacy error code with an unknown meaning. eg. this is returned if a lower level call returned DMA_MAPPING_ERROR.

-EREMOTEIO

The DMA device cannot access P2PDMA memory specified in the sg_table. This will not succeed if retried.

bool dma_can_mmap(struct device *dev)¶: check if a given device supports dma_mmap_*

Parameters

struct device *dev: device to check

Description

Returns true if dev supports dma_mmap_coherent() and dma_mmap_attrs() to map DMA allocations to userspace.

int dma_mmap_attrs(struct device *dev, struct vm_area_struct *vma, void *cpu_addr, dma_addr_t dma_addr, size_t size, unsigned long attrs)¶: map a coherent DMA allocation into user space

Parameters

struct device *dev: valid struct device pointer, or NULL for ISA and EISA-like devices
struct vm_area_struct *vma: vm_area_struct describing requested user mapping
void *cpu_addr: kernel CPU-view address returned from dma_alloc_attrs
dma_addr_t dma_addr: device-view address returned from dma_alloc_attrs
size_t size: size of memory originally requested in dma_alloc_attrs
unsigned long attrs: attributes of mapping properties requested in dma_alloc_attrs

Description

Map a coherent DMA buffer previously allocated by dma_alloc_attrs into user space. The coherent DMA buffer must not be freed by the driver until the user space mapping has been released.

bool dma_addressing_limited(struct device *dev)¶: return if the device is addressing limited

Parameters

struct device *dev: device to check

Description

Return true if the devices DMA mask is too small to address all memory in the system, else false. Lack of addressing bits is the prime reason for bounce buffering, but might not be the only one.

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

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.

int __devm_uio_register_device(struct module *owner, struct device *parent, struct uio_info *info)¶: Resource managed uio_register_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;
    dma_addr_t dma_addr;
    unsigned long           offs;
    resource_size_t size;
    int memtype;
    void __iomem            *internal_addr;
    struct device           *dma_device;
    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)
dma_addr: DMA handle set by dma_alloc_coherent, used with UIO_MEM_DMA_COHERENT only (addr should be the void * returned from the same dma_alloc_coherent call)
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
dma_device: device struct that was passed to dma_alloc_coherent, used with UIO_MEM_DMA_COHERENT only
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[MAX_UIO_MAPS];
    struct uio_port         port[MAX_UIO_PORT_REGIONS];
    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

uio_register_device¶

uio_register_device (parent, info)

register a new userspace IO device

Parameters

parent: parent device
info: UIO device capabilities

Description

returns zero on success or a negative error code.

devm_uio_register_device¶

devm_uio_register_device (parent, info)

Resource managed uio_register_device()

Parameters

parent: parent device
info: UIO device capabilities

Description

returns zero on success or a negative error code.

The Linux Kernel

Contents

This Page

Device drivers infrastructure¶

The Basic Device Driver-Model Structures¶

Device Drivers Base¶

Device Drivers DMA Management¶

Device drivers PnP support¶

Userspace IO devices¶