Linux generic IRQ handling

Copyright:© 2005-2010: Thomas Gleixner
Copyright:© 2005-2006: Ingo Molnar

Introduction

The generic interrupt handling layer is designed to provide a complete abstraction of interrupt handling for device drivers. It is able to handle all the different types of interrupt controller hardware. Device drivers use generic API functions to request, enable, disable and free interrupts. The drivers do not have to know anything about interrupt hardware details, so they can be used on different platforms without code changes.

This documentation is provided to developers who want to implement an interrupt subsystem based for their architecture, with the help of the generic IRQ handling layer.

Rationale

The original implementation of interrupt handling in Linux uses the __do_IRQ() super-handler, which is able to deal with every type of interrupt logic.

Originally, Russell King identified different types of handlers to build a quite universal set for the ARM interrupt handler implementation in Linux 2.5/2.6. He distinguished between:

  • Level type
  • Edge type
  • Simple type

During the implementation we identified another type:

  • Fast EOI type

In the SMP world of the __do_IRQ() super-handler another type was identified:

  • Per CPU type

This split implementation of high-level IRQ handlers allows us to optimize the flow of the interrupt handling for each specific interrupt type. This reduces complexity in that particular code path and allows the optimized handling of a given type.

The original general IRQ implementation used hw_interrupt_type structures and their ->ack, ->end [etc.] callbacks to differentiate the flow control in the super-handler. This leads to a mix of flow logic and low-level hardware logic, and it also leads to unnecessary code duplication: for example in i386, there is an ioapic_level_irq and an ioapic_edge_irq IRQ-type which share many of the low-level details but have different flow handling.

A more natural abstraction is the clean separation of the ‘irq flow’ and the ‘chip details’.

Analysing a couple of architecture’s IRQ subsystem implementations reveals that most of them can use a generic set of ‘irq flow’ methods and only need to add the chip-level specific code. The separation is also valuable for (sub)architectures which need specific quirks in the IRQ flow itself but not in the chip details - and thus provides a more transparent IRQ subsystem design.

Each interrupt descriptor is assigned its own high-level flow handler, which is normally one of the generic implementations. (This high-level flow handler implementation also makes it simple to provide demultiplexing handlers which can be found in embedded platforms on various architectures.)

The separation makes the generic interrupt handling layer more flexible and extensible. For example, an (sub)architecture can use a generic IRQ-flow implementation for ‘level type’ interrupts and add a (sub)architecture specific ‘edge type’ implementation.

To make the transition to the new model easier and prevent the breakage of existing implementations, the __do_IRQ() super-handler is still available. This leads to a kind of duality for the time being. Over time the new model should be used in more and more architectures, as it enables smaller and cleaner IRQ subsystems. It’s deprecated for three years now and about to be removed.

Known Bugs And Assumptions

None (knock on wood).

Abstraction layers

There are three main levels of abstraction in the interrupt code:

  1. High-level driver API
  2. High-level IRQ flow handlers
  3. Chip-level hardware encapsulation

Interrupt control flow

Each interrupt is described by an interrupt descriptor structure irq_desc. The interrupt is referenced by an ‘unsigned int’ numeric value which selects the corresponding interrupt description structure in the descriptor structures array. The descriptor structure contains status information and pointers to the interrupt flow method and the interrupt chip structure which are assigned to this interrupt.

Whenever an interrupt triggers, the low-level architecture code calls into the generic interrupt code by calling desc->handle_irq(). This high-level IRQ handling function only uses desc->irq_data.chip primitives referenced by the assigned chip descriptor structure.

High-level Driver API

The high-level Driver API consists of following functions:

See the autogenerated function documentation for details.

High-level IRQ flow handlers

The generic layer provides a set of pre-defined irq-flow methods:

The interrupt flow handlers (either pre-defined or architecture specific) are assigned to specific interrupts by the architecture either during bootup or during device initialization.

Default flow implementations

Helper functions

The helper functions call the chip primitives and are used by the default flow implementations. The following helper functions are implemented (simplified excerpt):

default_enable(struct irq_data *data)
{
    desc->irq_data.chip->irq_unmask(data);
}

default_disable(struct irq_data *data)
{
    if (!delay_disable(data))
        desc->irq_data.chip->irq_mask(data);
}

default_ack(struct irq_data *data)
{
    chip->irq_ack(data);
}

default_mask_ack(struct irq_data *data)
{
    if (chip->irq_mask_ack) {
        chip->irq_mask_ack(data);
    } else {
        chip->irq_mask(data);
        chip->irq_ack(data);
    }
}

noop(struct irq_data *data))
{
}

Default flow handler implementations

Default Level IRQ flow handler

handle_level_irq provides a generic implementation for level-triggered interrupts.

The following control flow is implemented (simplified excerpt):

:c:func:`desc->irq_data.chip->irq_mask_ack`;
handle_irq_event(desc->action);
:c:func:`desc->irq_data.chip->irq_unmask`;
Default Fast EOI IRQ flow handler

handle_fasteoi_irq provides a generic implementation for interrupts, which only need an EOI at the end of the handler.

The following control flow is implemented (simplified excerpt):

handle_irq_event(desc->action);
:c:func:`desc->irq_data.chip->irq_eoi`;
Default Edge IRQ flow handler

handle_edge_irq provides a generic implementation for edge-triggered interrupts.

The following control flow is implemented (simplified excerpt):

if (desc->status & running) {
    :c:func:`desc->irq_data.chip->irq_mask_ack`;
    desc->status |= pending | masked;
    return;
}
:c:func:`desc->irq_data.chip->irq_ack`;
desc->status |= running;
do {
    if (desc->status & masked)
        :c:func:`desc->irq_data.chip->irq_unmask`;
    desc->status &= ~pending;
    handle_irq_event(desc->action);
} while (status & pending);
desc->status &= ~running;
Default simple IRQ flow handler

handle_simple_irq provides a generic implementation for simple interrupts.

Note

The simple flow handler does not call any handler/chip primitives.

The following control flow is implemented (simplified excerpt):

handle_irq_event(desc->action);
Default per CPU flow handler

handle_percpu_irq provides a generic implementation for per CPU interrupts.

Per CPU interrupts are only available on SMP and the handler provides a simplified version without locking.

The following control flow is implemented (simplified excerpt):

if (desc->irq_data.chip->irq_ack)
    :c:func:`desc->irq_data.chip->irq_ack`;
handle_irq_event(desc->action);
if (desc->irq_data.chip->irq_eoi)
        :c:func:`desc->irq_data.chip->irq_eoi`;
EOI Edge IRQ flow handler

handle_edge_eoi_irq provides an abnomination of the edge handler which is solely used to tame a badly wreckaged irq controller on powerpc/cell.

Bad IRQ flow handler

handle_bad_irq is used for spurious interrupts which have no real handler assigned..

Quirks and optimizations

The generic functions are intended for ‘clean’ architectures and chips, which have no platform-specific IRQ handling quirks. If an architecture needs to implement quirks on the ‘flow’ level then it can do so by overriding the high-level irq-flow handler.

Delayed interrupt disable

This per interrupt selectable feature, which was introduced by Russell King in the ARM interrupt implementation, does not mask an interrupt at the hardware level when disable_irq() is called. The interrupt is kept enabled and is masked in the flow handler when an interrupt event happens. This prevents losing edge interrupts on hardware which does not store an edge interrupt event while the interrupt is disabled at the hardware level. When an interrupt arrives while the IRQ_DISABLED flag is set, then the interrupt is masked at the hardware level and the IRQ_PENDING bit is set. When the interrupt is re-enabled by enable_irq() the pending bit is checked and if it is set, the interrupt is resent either via hardware or by a software resend mechanism. (It’s necessary to enable CONFIG_HARDIRQS_SW_RESEND when you want to use the delayed interrupt disable feature and your hardware is not capable of retriggering an interrupt.) The delayed interrupt disable is not configurable.

Chip-level hardware encapsulation

The chip-level hardware descriptor structure irq_chip contains all the direct chip relevant functions, which can be utilized by the irq flow implementations.

  • irq_ack
  • irq_mask_ack - Optional, recommended for performance
  • irq_mask
  • irq_unmask
  • irq_eoi - Optional, required for EOI flow handlers
  • irq_retrigger - Optional
  • irq_set_type - Optional
  • irq_set_wake - Optional

These primitives are strictly intended to mean what they say: ack means ACK, masking means masking of an IRQ line, etc. It is up to the flow handler(s) to use these basic units of low-level functionality.

__do_IRQ entry point

The original implementation __do_IRQ() was an alternative entry point for all types of interrupts. It no longer exists.

This handler turned out to be not suitable for all interrupt hardware and was therefore reimplemented with split functionality for edge/level/simple/percpu interrupts. This is not only a functional optimization. It also shortens code paths for interrupts.

Locking on SMP

The locking of chip registers is up to the architecture that defines the chip primitives. The per-irq structure is protected via desc->lock, by the generic layer.

Generic interrupt chip

To avoid copies of identical implementations of IRQ chips the core provides a configurable generic interrupt chip implementation. Developers should check carefully whether the generic chip fits their needs before implementing the same functionality slightly differently themselves.

void irq_gc_mask_set_bit(struct irq_data * d)

Mask chip via setting bit in mask register

Parameters

struct irq_data * d
irq_data

Description

Chip has a single mask register. Values of this register are cached and protected by gc->lock

void irq_gc_mask_clr_bit(struct irq_data * d)

Mask chip via clearing bit in mask register

Parameters

struct irq_data * d
irq_data

Description

Chip has a single mask register. Values of this register are cached and protected by gc->lock

void irq_gc_ack_set_bit(struct irq_data * d)

Ack pending interrupt via setting bit

Parameters

struct irq_data * d
irq_data
struct irq_chip_generic * irq_alloc_generic_chip(const char * name, int num_ct, unsigned int irq_base, void __iomem * reg_base, irq_flow_handler_t handler)

Allocate a generic chip and initialize it

Parameters

const char * name
Name of the irq chip
int num_ct
Number of irq_chip_type instances associated with this
unsigned int irq_base
Interrupt base nr for this chip
void __iomem * reg_base
Register base address (virtual)
irq_flow_handler_t handler
Default flow handler associated with this chip

Description

Returns an initialized irq_chip_generic structure. The chip defaults to the primary (index 0) irq_chip_type and handler

int __irq_alloc_domain_generic_chips(struct irq_domain * d, int irqs_per_chip, int num_ct, const char * name, irq_flow_handler_t handler, unsigned int clr, unsigned int set, enum irq_gc_flags gcflags)

Allocate generic chips for an irq domain

Parameters

struct irq_domain * d
irq domain for which to allocate chips
int irqs_per_chip
Number of interrupts each chip handles (max 32)
int num_ct
Number of irq_chip_type instances associated with this
const char * name
Name of the irq chip
irq_flow_handler_t handler
Default flow handler associated with these chips
unsigned int clr
IRQ_* bits to clear in the mapping function
unsigned int set
IRQ_* bits to set in the mapping function
enum irq_gc_flags gcflags
Generic chip specific setup flags
struct irq_chip_generic * irq_get_domain_generic_chip(struct irq_domain * d, unsigned int hw_irq)

Get a pointer to the generic chip of a hw_irq

Parameters

struct irq_domain * d
irq domain pointer
unsigned int hw_irq
Hardware interrupt number
void irq_setup_generic_chip(struct irq_chip_generic * gc, u32 msk, enum irq_gc_flags flags, unsigned int clr, unsigned int set)

Setup a range of interrupts with a generic chip

Parameters

struct irq_chip_generic * gc
Generic irq chip holding all data
u32 msk
Bitmask holding the irqs to initialize relative to gc->irq_base
enum irq_gc_flags flags
Flags for initialization
unsigned int clr
IRQ_* bits to clear
unsigned int set
IRQ_* bits to set

Description

Set up max. 32 interrupts starting from gc->irq_base. Note, this initializes all interrupts to the primary irq_chip_type and its associated handler.

int irq_setup_alt_chip(struct irq_data * d, unsigned int type)

Switch to alternative chip

Parameters

struct irq_data * d
irq_data for this interrupt
unsigned int type
Flow type to be initialized

Description

Only to be called from chip->:c:func:irq_set_type() callbacks.

void irq_remove_generic_chip(struct irq_chip_generic * gc, u32 msk, unsigned int clr, unsigned int set)

Remove a chip

Parameters

struct irq_chip_generic * gc
Generic irq chip holding all data
u32 msk
Bitmask holding the irqs to initialize relative to gc->irq_base
unsigned int clr
IRQ_* bits to clear
unsigned int set
IRQ_* bits to set

Description

Remove up to 32 interrupts starting from gc->irq_base.

Structures

This chapter contains the autogenerated documentation of the structures which are used in the generic IRQ layer.

struct irq_common_data

per irq data shared by all irqchips

Definition

struct irq_common_data {
  unsigned int __private state_use_accessors;
#ifdef CONFIG_NUMA
  unsigned int node;
#endif
  void * handler_data;
  struct msi_desc * msi_desc;
  cpumask_var_t affinity;
#ifdef CONFIG_GENERIC_IRQ_IPI
  unsigned int ipi_offset;
#endif
};

Members

state_use_accessors
status information for irq chip functions. Use accessor functions to deal with it
node
node index useful for balancing
handler_data
per-IRQ data for the irq_chip methods
msi_desc
MSI descriptor
affinity
IRQ affinity on SMP. If this is an IPI related irq, then this is the mask of the CPUs to which an IPI can be sent.
ipi_offset
Offset of first IPI target cpu in affinity. Optional.
struct irq_data

per irq chip data passed down to chip functions

Definition

struct irq_data {
  u32 mask;
  unsigned int irq;
  unsigned long hwirq;
  struct irq_common_data * common;
  struct irq_chip * chip;
  struct irq_domain * domain;
#ifdef CONFIG_IRQ_DOMAIN_HIERARCHY
  struct irq_data * parent_data;
#endif
  void * chip_data;
};

Members

mask
precomputed bitmask for accessing the chip registers
irq
interrupt number
hwirq
hardware interrupt number, local to the interrupt domain
common
point to data shared by all irqchips
chip
low level interrupt hardware access
domain
Interrupt translation domain; responsible for mapping between hwirq number and linux irq number.
parent_data
pointer to parent struct irq_data to support hierarchy irq_domain
chip_data
platform-specific per-chip private data for the chip methods, to allow shared chip implementations
struct irq_chip

hardware interrupt chip descriptor

Definition

struct irq_chip {
  struct device * parent_device;
  const char * name;
  unsigned int        (* irq_startup) (struct irq_data *data);
  void (* irq_shutdown) (struct irq_data *data);
  void (* irq_enable) (struct irq_data *data);
  void (* irq_disable) (struct irq_data *data);
  void (* irq_ack) (struct irq_data *data);
  void (* irq_mask) (struct irq_data *data);
  void (* irq_mask_ack) (struct irq_data *data);
  void (* irq_unmask) (struct irq_data *data);
  void (* irq_eoi) (struct irq_data *data);
  int (* irq_set_affinity) (struct irq_data *data, const struct cpumask *dest, bool force);
  int (* irq_retrigger) (struct irq_data *data);
  int (* irq_set_type) (struct irq_data *data, unsigned int flow_type);
  int (* irq_set_wake) (struct irq_data *data, unsigned int on);
  void (* irq_bus_lock) (struct irq_data *data);
  void (* irq_bus_sync_unlock) (struct irq_data *data);
  void (* irq_cpu_online) (struct irq_data *data);
  void (* irq_cpu_offline) (struct irq_data *data);
  void (* irq_suspend) (struct irq_data *data);
  void (* irq_resume) (struct irq_data *data);
  void (* irq_pm_shutdown) (struct irq_data *data);
  void (* irq_calc_mask) (struct irq_data *data);
  void (* irq_print_chip) (struct irq_data *data, struct seq_file *p);
  int (* irq_request_resources) (struct irq_data *data);
  void (* irq_release_resources) (struct irq_data *data);
  void (* irq_compose_msi_msg) (struct irq_data *data, struct msi_msg *msg);
  void (* irq_write_msi_msg) (struct irq_data *data, struct msi_msg *msg);
  int (* irq_get_irqchip_state) (struct irq_data *data, enum irqchip_irq_state which, bool *state);
  int (* irq_set_irqchip_state) (struct irq_data *data, enum irqchip_irq_state which, bool state);
  int (* irq_set_vcpu_affinity) (struct irq_data *data, void *vcpu_info);
  void (* ipi_send_single) (struct irq_data *data, unsigned int cpu);
  void (* ipi_send_mask) (struct irq_data *data, const struct cpumask *dest);
  unsigned long flags;
};

Members

parent_device
pointer to parent device for irqchip
name
name for /proc/interrupts
irq_startup
start up the interrupt (defaults to ->enable if NULL)
irq_shutdown
shut down the interrupt (defaults to ->disable if NULL)
irq_enable
enable the interrupt (defaults to chip->unmask if NULL)
irq_disable
disable the interrupt
irq_ack
start of a new interrupt
irq_mask
mask an interrupt source
irq_mask_ack
ack and mask an interrupt source
irq_unmask
unmask an interrupt source
irq_eoi
end of interrupt
irq_set_affinity
set the CPU affinity on SMP machines
irq_retrigger
resend an IRQ to the CPU
irq_set_type
set the flow type (IRQ_TYPE_LEVEL/etc.) of an IRQ
irq_set_wake
enable/disable power-management wake-on of an IRQ
irq_bus_lock
function to lock access to slow bus (i2c) chips
irq_bus_sync_unlock
function to sync and unlock slow bus (i2c) chips
irq_cpu_online
configure an interrupt source for a secondary CPU
irq_cpu_offline
un-configure an interrupt source for a secondary CPU
irq_suspend
function called from core code on suspend once per chip, when one or more interrupts are installed
irq_resume
function called from core code on resume once per chip, when one ore more interrupts are installed
irq_pm_shutdown
function called from core code on shutdown once per chip
irq_calc_mask
Optional function to set irq_data.mask for special cases
irq_print_chip
optional to print special chip info in show_interrupts
irq_request_resources
optional to request resources before calling any other callback related to this irq
irq_release_resources
optional to release resources acquired with irq_request_resources
irq_compose_msi_msg
optional to compose message content for MSI
irq_write_msi_msg
optional to write message content for MSI
irq_get_irqchip_state
return the internal state of an interrupt
irq_set_irqchip_state
set the internal state of a interrupt
irq_set_vcpu_affinity
optional to target a vCPU in a virtual machine
ipi_send_single
send a single IPI to destination cpus
ipi_send_mask
send an IPI to destination cpus in cpumask
flags
chip specific flags
struct irq_chip_regs

register offsets for struct irq_gci

Definition

struct irq_chip_regs {
  unsigned long enable;
  unsigned long disable;
  unsigned long mask;
  unsigned long ack;
  unsigned long eoi;
  unsigned long type;
  unsigned long polarity;
};

Members

enable
Enable register offset to reg_base
disable
Disable register offset to reg_base
mask
Mask register offset to reg_base
ack
Ack register offset to reg_base
eoi
Eoi register offset to reg_base
type
Type configuration register offset to reg_base
polarity
Polarity configuration register offset to reg_base
struct irq_chip_type

Generic interrupt chip instance for a flow type

Definition

struct irq_chip_type {
  struct irq_chip chip;
  struct irq_chip_regs regs;
  irq_flow_handler_t handler;
  u32 type;
  u32 mask_cache_priv;
  u32 * mask_cache;
};

Members

chip
The real interrupt chip which provides the callbacks
regs
Register offsets for this chip
handler
Flow handler associated with this chip
type
Chip can handle these flow types
mask_cache_priv
Cached mask register private to the chip type
mask_cache
Pointer to cached mask register

Description

A irq_generic_chip can have several instances of irq_chip_type when it requires different functions and register offsets for different flow types.

struct irq_chip_generic

Generic irq chip data structure

Definition

struct irq_chip_generic {
  raw_spinlock_t lock;
  void __iomem * reg_base;
  u32 (* reg_readl) (void __iomem *addr);
  void (* reg_writel) (u32 val, void __iomem *addr);
  void (* suspend) (struct irq_chip_generic *gc);
  void (* resume) (struct irq_chip_generic *gc);
  unsigned int irq_base;
  unsigned int irq_cnt;
  u32 mask_cache;
  u32 type_cache;
  u32 polarity_cache;
  u32 wake_enabled;
  u32 wake_active;
  unsigned int num_ct;
  void * private;
  unsigned long installed;
  unsigned long unused;
  struct irq_domain * domain;
  struct list_head list;
  struct irq_chip_type chip_types;
};

Members

lock
Lock to protect register and cache data access
reg_base
Register base address (virtual)
reg_readl
Alternate I/O accessor (defaults to readl if NULL)
reg_writel
Alternate I/O accessor (defaults to writel if NULL)
suspend
Function called from core code on suspend once per chip; can be useful instead of irq_chip::suspend to handle chip details even when no interrupts are in use
resume
Function called from core code on resume once per chip; can be useful instead of irq_chip::suspend to handle chip details even when no interrupts are in use
irq_base
Interrupt base nr for this chip
irq_cnt
Number of interrupts handled by this chip
mask_cache
Cached mask register shared between all chip types
type_cache
Cached type register
polarity_cache
Cached polarity register
wake_enabled
Interrupt can wakeup from suspend
wake_active
Interrupt is marked as an wakeup from suspend source
num_ct
Number of available irq_chip_type instances (usually 1)
private
Private data for non generic chip callbacks
installed
bitfield to denote installed interrupts
unused
bitfield to denote unused interrupts
domain
irq domain pointer
list
List head for keeping track of instances
chip_types
Array of interrupt irq_chip_types

Description

Note, that irq_chip_generic can have multiple irq_chip_type implementations which can be associated to a particular irq line of an irq_chip_generic instance. That allows to share and protect state in an irq_chip_generic instance when we need to implement different flow mechanisms (level/edge) for it.

enum irq_gc_flags

Initialization flags for generic irq chips

Constants

IRQ_GC_INIT_MASK_CACHE
Initialize the mask_cache by reading mask reg
IRQ_GC_INIT_NESTED_LOCK
Set the lock class of the irqs to nested for irq chips which need to call irq_set_wake() on the parent irq. Usually GPIO implementations
IRQ_GC_MASK_CACHE_PER_TYPE
Mask cache is chip type private
IRQ_GC_NO_MASK
Do not calculate irq_data->mask
IRQ_GC_BE_IO
Use big-endian register accesses (default: LE)
struct irqaction

per interrupt action descriptor

Definition

struct irqaction {
  irq_handler_t handler;
  void * dev_id;
  void __percpu * percpu_dev_id;
  struct irqaction * next;
  irq_handler_t thread_fn;
  struct task_struct * thread;
  struct irqaction * secondary;
  unsigned int irq;
  unsigned int flags;
  unsigned long thread_flags;
  unsigned long thread_mask;
  const char * name;
  struct proc_dir_entry * dir;
};

Members

handler
interrupt handler function
dev_id
cookie to identify the device
percpu_dev_id
cookie to identify the device
next
pointer to the next irqaction for shared interrupts
thread_fn
interrupt handler function for threaded interrupts
thread
thread pointer for threaded interrupts
secondary
pointer to secondary irqaction (force threading)
irq
interrupt number
flags
flags (see IRQF_* above)
thread_flags
flags related to thread
thread_mask
bitmask for keeping track of thread activity
name
name of the device
dir
pointer to the proc/irq/NN/name entry
struct irq_affinity_notify

context for notification of IRQ affinity changes

Definition

struct irq_affinity_notify {
  unsigned int irq;
  struct kref kref;
  struct work_struct work;
  void (* notify) (struct irq_affinity_notify *, const cpumask_t *mask);
  void (* release) (struct kref *ref);
};

Members

irq
Interrupt to which notification applies
kref
Reference count, for internal use
work
Work item, for internal use
notify
Function to be called on change. This will be called in process context.
release
Function to be called on release. This will be called in process context. Once registered, the structure must only be freed when this function is called or later.
struct irq_affinity

Description for automatic irq affinity assignements

Definition

struct irq_affinity {
  int pre_vectors;
  int post_vectors;
};

Members

pre_vectors
Don’t apply affinity to pre_vectors at beginning of the MSI(-X) vector space
post_vectors
Don’t apply affinity to post_vectors at end of the MSI(-X) vector space
int irq_set_affinity(unsigned int irq, const struct cpumask * cpumask)

Set the irq affinity of a given irq

Parameters

unsigned int irq
Interrupt to set affinity
const struct cpumask * cpumask
cpumask

Description

Fails if cpumask does not contain an online CPU

int irq_force_affinity(unsigned int irq, const struct cpumask * cpumask)

Force the irq affinity of a given irq

Parameters

unsigned int irq
Interrupt to set affinity
const struct cpumask * cpumask
cpumask

Description

Same as irq_set_affinity, but without checking the mask against online cpus.

Solely for low level cpu hotplug code, where we need to make per cpu interrupts affine before the cpu becomes online.

Public Functions Provided

This chapter contains the autogenerated documentation of the kernel API functions which are exported.

bool synchronize_hardirq(unsigned int irq)

wait for pending hard IRQ handlers (on other CPUs)

Parameters

unsigned int irq
interrupt number to wait for

Description

This function waits for any pending hard IRQ handlers for this interrupt to complete before returning. If you use this function while holding a resource the IRQ handler may need you will deadlock. It does not take associated threaded handlers into account.

Do not use this for shutdown scenarios where you must be sure that all parts (hardirq and threaded handler) have completed.

Return

false if a threaded handler is active.

This function may be called - with care - from IRQ context.
void synchronize_irq(unsigned int irq)

wait for pending IRQ handlers (on other CPUs)

Parameters

unsigned int irq
interrupt number to wait for

Description

This function waits for any pending IRQ handlers for this interrupt to complete before returning. If you use this function while holding a resource the IRQ handler may need you will deadlock.

This function may be called - with care - from IRQ context.

int irq_can_set_affinity(unsigned int irq)

Check if the affinity of a given irq can be set

Parameters

unsigned int irq
Interrupt to check
bool irq_can_set_affinity_usr(unsigned int irq)

Check if affinity of a irq can be set from user space

Parameters

unsigned int irq
Interrupt to check

Description

Like irq_can_set_affinity() above, but additionally checks for the AFFINITY_MANAGED flag.

void irq_set_thread_affinity(struct irq_desc * desc)

Notify irq threads to adjust affinity

Parameters

struct irq_desc * desc
irq descriptor which has affitnity changed

Description

We just set IRQTF_AFFINITY and delegate the affinity setting to the interrupt thread itself. We can not call set_cpus_allowed_ptr() here as we hold desc->lock and this code can be called from hard interrupt context.
int irq_set_affinity_notifier(unsigned int irq, struct irq_affinity_notify * notify)

control notification of IRQ affinity changes

Parameters

unsigned int irq
Interrupt for which to enable/disable notification
struct irq_affinity_notify * notify
Context for notification, or NULL to disable notification. Function pointers must be initialised; the other fields will be initialised by this function.

Description

Must be called in process context. Notification may only be enabled after the IRQ is allocated and must be disabled before the IRQ is freed using free_irq().
int irq_set_vcpu_affinity(unsigned int irq, void * vcpu_info)

Set vcpu affinity for the interrupt

Parameters

unsigned int irq
interrupt number to set affinity
void * vcpu_info
vCPU specific data

Description

This function uses the vCPU specific data to set the vCPU affinity for an irq. The vCPU specific data is passed from outside, such as KVM. One example code path is as below: KVM -> IOMMU -> irq_set_vcpu_affinity().
void disable_irq_nosync(unsigned int irq)

disable an irq without waiting

Parameters

unsigned int irq
Interrupt to disable

Description

Disable the selected interrupt line. Disables and Enables are nested. Unlike disable_irq(), this function does not ensure existing instances of the IRQ handler have completed before returning.

This function may be called from IRQ context.

void disable_irq(unsigned int irq)

disable an irq and wait for completion

Parameters

unsigned int irq
Interrupt to disable

Description

Disable the selected interrupt line. Enables and Disables are nested. This function waits for any pending IRQ handlers for this interrupt to complete before returning. If you use this function while holding a resource the IRQ handler may need you will deadlock.

This function may be called - with care - from IRQ context.

bool disable_hardirq(unsigned int irq)

disables an irq and waits for hardirq completion

Parameters

unsigned int irq
Interrupt to disable

Description

Disable the selected interrupt line. Enables and Disables are nested. This function waits for any pending hard IRQ handlers for this interrupt to complete before returning. If you use this function while holding a resource the hard IRQ handler may need you will deadlock.

When used to optimistically disable an interrupt from atomic context the return value must be checked.

Return

false if a threaded handler is active.

This function may be called - with care - from IRQ context.
void enable_irq(unsigned int irq)

enable handling of an irq

Parameters

unsigned int irq
Interrupt to enable

Description

Undoes the effect of one call to disable_irq(). If this matches the last disable, processing of interrupts on this IRQ line is re-enabled.

This function may be called from IRQ context only when desc->irq_data.chip->bus_lock and desc->chip->bus_sync_unlock are NULL !

int irq_set_irq_wake(unsigned int irq, unsigned int on)

control irq power management wakeup

Parameters

unsigned int irq
interrupt to control
unsigned int on
enable/disable power management wakeup

Description

Enable/disable power management wakeup mode, which is disabled by default. Enables and disables must match, just as they match for non-wakeup mode support.

Wakeup mode lets this IRQ wake the system from sleep states like “suspend to RAM”.

void irq_wake_thread(unsigned int irq, void * dev_id)

wake the irq thread for the action identified by dev_id

Parameters

unsigned int irq
Interrupt line
void * dev_id
Device identity for which the thread should be woken
int setup_irq(unsigned int irq, struct irqaction * act)

setup an interrupt

Parameters

unsigned int irq
Interrupt line to setup
struct irqaction * act
irqaction for the interrupt

Description

Used to statically setup interrupts in the early boot process.

void remove_irq(unsigned int irq, struct irqaction * act)

free an interrupt

Parameters

unsigned int irq
Interrupt line to free
struct irqaction * act
irqaction for the interrupt

Description

Used to remove interrupts statically setup by the early boot process.

const void * free_irq(unsigned int irq, void * dev_id)

free an interrupt allocated with request_irq

Parameters

unsigned int irq
Interrupt line to free
void * dev_id
Device identity to free

Description

Remove an interrupt handler. The handler is removed and if the interrupt line is no longer in use by any driver it is disabled. On a shared IRQ the caller must ensure the interrupt is disabled on the card it drives before calling this function. The function does not return until any executing interrupts for this IRQ have completed.

This function must not be called from interrupt context.

Returns the devname argument passed to request_irq.

int request_threaded_irq(unsigned int irq, irq_handler_t handler, irq_handler_t thread_fn, unsigned long irqflags, const char * devname, void * dev_id)

allocate an interrupt line

Parameters

unsigned int irq
Interrupt line to allocate
irq_handler_t handler
Function to be called when the IRQ occurs. Primary handler for threaded interrupts If NULL and thread_fn != NULL the default primary handler is installed
irq_handler_t thread_fn
Function called from the irq handler thread If NULL, no irq thread is created
unsigned long irqflags
Interrupt type flags
const char * devname
An ascii name for the claiming device
void * dev_id
A cookie passed back to the handler function

Description

This call allocates interrupt resources and enables the interrupt line and IRQ handling. From the point this call is made your handler function may be invoked. Since your handler function must clear any interrupt the board raises, you must take care both to initialise your hardware and to set up the interrupt handler in the right order.

If you want to set up a threaded irq handler for your device then you need to supply handler and thread_fn. handler is still called in hard interrupt context and has to check whether the interrupt originates from the device. If yes it needs to disable the interrupt on the device and return IRQ_WAKE_THREAD which will wake up the handler thread and run thread_fn. This split handler design is necessary to support shared interrupts.

Dev_id must be globally unique. Normally the address of the device data structure is used as the cookie. Since the handler receives this value it makes sense to use it.

If your interrupt is shared you must pass a non NULL dev_id as this is required when freeing the interrupt.

Flags:

IRQF_SHARED Interrupt is shared IRQF_TRIGGER_* Specify active edge(s) or level

int request_any_context_irq(unsigned int irq, irq_handler_t handler, unsigned long flags, const char * name, void * dev_id)

allocate an interrupt line

Parameters

unsigned int irq
Interrupt line to allocate
irq_handler_t handler
Function to be called when the IRQ occurs. Threaded handler for threaded interrupts.
unsigned long flags
Interrupt type flags
const char * name
An ascii name for the claiming device
void * dev_id
A cookie passed back to the handler function

Description

This call allocates interrupt resources and enables the interrupt line and IRQ handling. It selects either a hardirq or threaded handling method depending on the context.

On failure, it returns a negative value. On success, it returns either IRQC_IS_HARDIRQ or IRQC_IS_NESTED.

bool irq_percpu_is_enabled(unsigned int irq)

Check whether the per cpu irq is enabled

Parameters

unsigned int irq
Linux irq number to check for

Description

Must be called from a non migratable context. Returns the enable state of a per cpu interrupt on the current cpu.

void remove_percpu_irq(unsigned int irq, struct irqaction * act)

free a per-cpu interrupt

Parameters

unsigned int irq
Interrupt line to free
struct irqaction * act
irqaction for the interrupt

Description

Used to remove interrupts statically setup by the early boot process.

void free_percpu_irq(unsigned int irq, void __percpu * dev_id)

free an interrupt allocated with request_percpu_irq

Parameters

unsigned int irq
Interrupt line to free
void __percpu * dev_id
Device identity to free

Description

Remove a percpu interrupt handler. The handler is removed, but the interrupt line is not disabled. This must be done on each CPU before calling this function. The function does not return until any executing interrupts for this IRQ have completed.

This function must not be called from interrupt context.

int setup_percpu_irq(unsigned int irq, struct irqaction * act)

setup a per-cpu interrupt

Parameters

unsigned int irq
Interrupt line to setup
struct irqaction * act
irqaction for the interrupt

Description

Used to statically setup per-cpu interrupts in the early boot process.

int request_percpu_irq(unsigned int irq, irq_handler_t handler, const char * devname, void __percpu * dev_id)

allocate a percpu interrupt line

Parameters

unsigned int irq
Interrupt line to allocate
irq_handler_t handler
Function to be called when the IRQ occurs.
const char * devname
An ascii name for the claiming device
void __percpu * dev_id
A percpu cookie passed back to the handler function

Description

This call allocates interrupt resources and enables the interrupt on the local CPU. If the interrupt is supposed to be enabled on other CPUs, it has to be done on each CPU using enable_percpu_irq().

Dev_id must be globally unique. It is a per-cpu variable, and the handler gets called with the interrupted CPU’s instance of that variable.

int irq_get_irqchip_state(unsigned int irq, enum irqchip_irq_state which, bool * state)

returns the irqchip state of a interrupt.

Parameters

unsigned int irq
Interrupt line that is forwarded to a VM
enum irqchip_irq_state which
One of IRQCHIP_STATE_* the caller wants to know about
bool * state
a pointer to a boolean where the state is to be storeed

Description

This call snapshots the internal irqchip state of an interrupt, returning into state the bit corresponding to stage which

This function should be called with preemption disabled if the interrupt controller has per-cpu registers.

int irq_set_irqchip_state(unsigned int irq, enum irqchip_irq_state which, bool val)

set the state of a forwarded interrupt.

Parameters

unsigned int irq
Interrupt line that is forwarded to a VM
enum irqchip_irq_state which
State to be restored (one of IRQCHIP_STATE_*)
bool val
Value corresponding to which

Description

This call sets the internal irqchip state of an interrupt, depending on the value of which.

This function should be called with preemption disabled if the interrupt controller has per-cpu registers.

int irq_set_chip(unsigned int irq, struct irq_chip * chip)

set the irq chip for an irq

Parameters

unsigned int irq
irq number
struct irq_chip * chip
pointer to irq chip description structure
int irq_set_irq_type(unsigned int irq, unsigned int type)

set the irq trigger type for an irq

Parameters

unsigned int irq
irq number
unsigned int type
IRQ_TYPE_{LEVEL,EDGE}_* value - see include/linux/irq.h
int irq_set_handler_data(unsigned int irq, void * data)

set irq handler data for an irq

Parameters

unsigned int irq
Interrupt number
void * data
Pointer to interrupt specific data

Description

Set the hardware irq controller data for an irq
int irq_set_msi_desc_off(unsigned int irq_base, unsigned int irq_offset, struct msi_desc * entry)

set MSI descriptor data for an irq at offset

Parameters

unsigned int irq_base
Interrupt number base
unsigned int irq_offset
Interrupt number offset
struct msi_desc * entry
Pointer to MSI descriptor data

Description

Set the MSI descriptor entry for an irq at offset
int irq_set_msi_desc(unsigned int irq, struct msi_desc * entry)

set MSI descriptor data for an irq

Parameters

unsigned int irq
Interrupt number
struct msi_desc * entry
Pointer to MSI descriptor data

Description

Set the MSI descriptor entry for an irq
int irq_set_chip_data(unsigned int irq, void * data)

set irq chip data for an irq

Parameters

unsigned int irq
Interrupt number
void * data
Pointer to chip specific data

Description

Set the hardware irq chip data for an irq
void irq_disable(struct irq_desc * desc)

Mark interrupt disabled

Parameters

struct irq_desc * desc
irq descriptor which should be disabled

Description

If the chip does not implement the irq_disable callback, we use a lazy disable approach. That means we mark the interrupt disabled, but leave the hardware unmasked. That’s an optimization because we avoid the hardware access for the common case where no interrupt happens after we marked it disabled. If an interrupt happens, then the interrupt flow handler masks the line at the hardware level and marks it pending.

If the interrupt chip does not implement the irq_disable callback, a driver can disable the lazy approach for a particular irq line by calling ‘irq_set_status_flags(irq, IRQ_DISABLE_UNLAZY)’. This can be used for devices which cannot disable the interrupt at the device level under certain circumstances and have to use disable_irq[_nosync] instead.

void handle_simple_irq(struct irq_desc * desc)

Simple and software-decoded IRQs.

Parameters

struct irq_desc * desc
the interrupt description structure for this irq

Description

Simple interrupts are either sent from a demultiplexing interrupt handler or come from hardware, where no interrupt hardware control is necessary.

Note

The caller is expected to handle the ack, clear, mask and
unmask issues if necessary.
void handle_untracked_irq(struct irq_desc * desc)

Simple and software-decoded IRQs.

Parameters

struct irq_desc * desc
the interrupt description structure for this irq

Description

Untracked interrupts are sent from a demultiplexing interrupt handler when the demultiplexer does not know which device it its multiplexed irq domain generated the interrupt. IRQ’s handled through here are not subjected to stats tracking, randomness, or spurious interrupt detection.

Note

Like handle_simple_irq, the caller is expected to handle
the ack, clear, mask and unmask issues if necessary.
void handle_level_irq(struct irq_desc * desc)

Level type irq handler

Parameters

struct irq_desc * desc
the interrupt description structure for this irq

Description

Level type interrupts are active as long as the hardware line has the active level. This may require to mask the interrupt and unmask it after the associated handler has acknowledged the device, so the interrupt line is back to inactive.
void handle_fasteoi_irq(struct irq_desc * desc)

irq handler for transparent controllers

Parameters

struct irq_desc * desc
the interrupt description structure for this irq

Description

Only a single callback will be issued to the chip: an ->:c:func:eoi() call when the interrupt has been serviced. This enables support for modern forms of interrupt handlers, which handle the flow details in hardware, transparently.
void handle_edge_irq(struct irq_desc * desc)

edge type IRQ handler

Parameters

struct irq_desc * desc
the interrupt description structure for this irq

Description

Interrupt occures on the falling and/or rising edge of a hardware signal. The occurrence is latched into the irq controller hardware and must be acked in order to be reenabled. After the ack another interrupt can happen on the same source even before the first one is handled by the associated event handler. If this happens it might be necessary to disable (mask) the interrupt depending on the controller hardware. This requires to reenable the interrupt inside of the loop which handles the interrupts which have arrived while the handler was running. If all pending interrupts are handled, the loop is left.
void handle_edge_eoi_irq(struct irq_desc * desc)

edge eoi type IRQ handler

Parameters

struct irq_desc * desc
the interrupt description structure for this irq

Description

Similar as the above handle_edge_irq, but using eoi and w/o the mask/unmask logic.

void handle_percpu_irq(struct irq_desc * desc)

Per CPU local irq handler

Parameters

struct irq_desc * desc
the interrupt description structure for this irq

Description

Per CPU interrupts on SMP machines without locking requirements
void handle_percpu_devid_irq(struct irq_desc * desc)

Per CPU local irq handler with per cpu dev ids

Parameters

struct irq_desc * desc
the interrupt description structure for this irq

Description

Per CPU interrupts on SMP machines without locking requirements. Same as handle_percpu_irq() above but with the following extras:

action->percpu_dev_id is a pointer to percpu variables which contain the real device id for the cpu on which this handler is called

void irq_cpu_online(void)

Invoke all irq_cpu_online functions.

Parameters

void
no arguments

Description

Iterate through all irqs and invoke the chip.:c:func:irq_cpu_online() for each.
void irq_cpu_offline(void)

Invoke all irq_cpu_offline functions.

Parameters

void
no arguments

Description

Iterate through all irqs and invoke the chip.:c:func:irq_cpu_offline() for each.
void irq_chip_enable_parent(struct irq_data * data)

Enable the parent interrupt (defaults to unmask if NULL)

Parameters

struct irq_data * data
Pointer to interrupt specific data
void irq_chip_disable_parent(struct irq_data * data)

Disable the parent interrupt (defaults to mask if NULL)

Parameters

struct irq_data * data
Pointer to interrupt specific data
void irq_chip_ack_parent(struct irq_data * data)

Acknowledge the parent interrupt

Parameters

struct irq_data * data
Pointer to interrupt specific data
void irq_chip_mask_parent(struct irq_data * data)

Mask the parent interrupt

Parameters

struct irq_data * data
Pointer to interrupt specific data
void irq_chip_unmask_parent(struct irq_data * data)

Unmask the parent interrupt

Parameters

struct irq_data * data
Pointer to interrupt specific data
void irq_chip_eoi_parent(struct irq_data * data)

Invoke EOI on the parent interrupt

Parameters

struct irq_data * data
Pointer to interrupt specific data
int irq_chip_set_affinity_parent(struct irq_data * data, const struct cpumask * dest, bool force)

Set affinity on the parent interrupt

Parameters

struct irq_data * data
Pointer to interrupt specific data
const struct cpumask * dest
The affinity mask to set
bool force
Flag to enforce setting (disable online checks)

Description

Conditinal, as the underlying parent chip might not implement it.

int irq_chip_set_type_parent(struct irq_data * data, unsigned int type)

Set IRQ type on the parent interrupt

Parameters

struct irq_data * data
Pointer to interrupt specific data
unsigned int type
IRQ_TYPE_{LEVEL,EDGE}_* value - see include/linux/irq.h

Description

Conditional, as the underlying parent chip might not implement it.

int irq_chip_retrigger_hierarchy(struct irq_data * data)

Retrigger an interrupt in hardware

Parameters

struct irq_data * data
Pointer to interrupt specific data

Description

Iterate through the domain hierarchy of the interrupt and check whether a hw retrigger function exists. If yes, invoke it.

int irq_chip_set_vcpu_affinity_parent(struct irq_data * data, void * vcpu_info)

Set vcpu affinity on the parent interrupt

Parameters

struct irq_data * data
Pointer to interrupt specific data
void * vcpu_info
The vcpu affinity information
int irq_chip_set_wake_parent(struct irq_data * data, unsigned int on)

Set/reset wake-up on the parent interrupt

Parameters

struct irq_data * data
Pointer to interrupt specific data
unsigned int on
Whether to set or reset the wake-up capability of this irq

Description

Conditional, as the underlying parent chip might not implement it.

int irq_chip_compose_msi_msg(struct irq_data * data, struct msi_msg * msg)

Componse msi message for a irq chip

Parameters

struct irq_data * data
Pointer to interrupt specific data
struct msi_msg * msg
Pointer to the MSI message

Description

For hierarchical domains we find the first chip in the hierarchy which implements the irq_compose_msi_msg callback. For non hierarchical we use the top level chip.

int irq_chip_pm_get(struct irq_data * data)

Enable power for an IRQ chip

Parameters

struct irq_data * data
Pointer to interrupt specific data

Description

Enable the power to the IRQ chip referenced by the interrupt data structure.

int irq_chip_pm_put(struct irq_data * data)

Disable power for an IRQ chip

Parameters

struct irq_data * data
Pointer to interrupt specific data

Description

Disable the power to the IRQ chip referenced by the interrupt data structure, belongs. Note that power will only be disabled, once this function has been called for all IRQs that have called irq_chip_pm_get().

Internal Functions Provided

This chapter contains the autogenerated documentation of the internal functions.

int generic_handle_irq(unsigned int irq)

Invoke the handler for a particular irq

Parameters

unsigned int irq
The irq number to handle
int __handle_domain_irq(struct irq_domain * domain, unsigned int hwirq, bool lookup, struct pt_regs * regs)

Invoke the handler for a HW irq belonging to a domain

Parameters

struct irq_domain * domain
The domain where to perform the lookup
unsigned int hwirq
The HW irq number to convert to a logical one
bool lookup
Whether to perform the domain lookup or not
struct pt_regs * regs
Register file coming from the low-level handling code

Return

0 on success, or -EINVAL if conversion has failed

void irq_free_descs(unsigned int from, unsigned int cnt)

free irq descriptors

Parameters

unsigned int from
Start of descriptor range
unsigned int cnt
Number of consecutive irqs to free
int __ref __irq_alloc_descs(int irq, unsigned int from, unsigned int cnt, int node, struct module * owner, const struct cpumask * affinity)

allocate and initialize a range of irq descriptors

Parameters

int irq
Allocate for specific irq number if irq >= 0
unsigned int from
Start the search from this irq number
unsigned int cnt
Number of consecutive irqs to allocate.
int node
Preferred node on which the irq descriptor should be allocated
struct module * owner
Owning module (can be NULL)
const struct cpumask * affinity
Optional pointer to an affinity mask array of size cnt which hints where the irq descriptors should be allocated and which default affinities to use

Description

Returns the first irq number or error code

unsigned int irq_alloc_hwirqs(int cnt, int node)

Allocate an irq descriptor and initialize the hardware

Parameters

int cnt
number of interrupts to allocate
int node
node on which to allocate

Description

Returns an interrupt number > 0 or 0, if the allocation fails.

void irq_free_hwirqs(unsigned int from, int cnt)

Free irq descriptor and cleanup the hardware

Parameters

unsigned int from
Free from irq number
int cnt
number of interrupts to free
unsigned int irq_get_next_irq(unsigned int offset)

get next allocated irq number

Parameters

unsigned int offset
where to start the search

Description

Returns next irq number after offset or nr_irqs if none is found.

unsigned int kstat_irqs_cpu(unsigned int irq, int cpu)

Get the statistics for an interrupt on a cpu

Parameters

unsigned int irq
The interrupt number
int cpu
The cpu number

Description

Returns the sum of interrupt counts on cpu since boot for irq. The caller must ensure that the interrupt is not removed concurrently.

unsigned int kstat_irqs(unsigned int irq)

Get the statistics for an interrupt

Parameters

unsigned int irq
The interrupt number

Description

Returns the sum of interrupt counts on all cpus since boot for irq. The caller must ensure that the interrupt is not removed concurrently.

unsigned int kstat_irqs_usr(unsigned int irq)

Get the statistics for an interrupt

Parameters

unsigned int irq
The interrupt number

Description

Returns the sum of interrupt counts on all cpus since boot for irq. Contrary to kstat_irqs() this can be called from any preemptible context. It’s protected against concurrent removal of an interrupt descriptor when sparse irqs are enabled.

void handle_bad_irq(struct irq_desc * desc)

handle spurious and unhandled irqs

Parameters

struct irq_desc * desc
description of the interrupt

Description

Handles spurious and unhandled IRQ’s. It also prints a debugmessage.

int irq_set_chip(unsigned int irq, struct irq_chip * chip)

set the irq chip for an irq

Parameters

unsigned int irq
irq number
struct irq_chip * chip
pointer to irq chip description structure
int irq_set_irq_type(unsigned int irq, unsigned int type)

set the irq trigger type for an irq

Parameters

unsigned int irq
irq number
unsigned int type
IRQ_TYPE_{LEVEL,EDGE}_* value - see include/linux/irq.h
int irq_set_handler_data(unsigned int irq, void * data)

set irq handler data for an irq

Parameters

unsigned int irq
Interrupt number
void * data
Pointer to interrupt specific data

Description

Set the hardware irq controller data for an irq
int irq_set_msi_desc_off(unsigned int irq_base, unsigned int irq_offset, struct msi_desc * entry)

set MSI descriptor data for an irq at offset

Parameters

unsigned int irq_base
Interrupt number base
unsigned int irq_offset
Interrupt number offset
struct msi_desc * entry
Pointer to MSI descriptor data

Description

Set the MSI descriptor entry for an irq at offset
int irq_set_msi_desc(unsigned int irq, struct msi_desc * entry)

set MSI descriptor data for an irq

Parameters

unsigned int irq
Interrupt number
struct msi_desc * entry
Pointer to MSI descriptor data

Description

Set the MSI descriptor entry for an irq
int irq_set_chip_data(unsigned int irq, void * data)

set irq chip data for an irq

Parameters

unsigned int irq
Interrupt number
void * data
Pointer to chip specific data

Description

Set the hardware irq chip data for an irq
void irq_disable(struct irq_desc * desc)

Mark interrupt disabled

Parameters

struct irq_desc * desc
irq descriptor which should be disabled

Description

If the chip does not implement the irq_disable callback, we use a lazy disable approach. That means we mark the interrupt disabled, but leave the hardware unmasked. That’s an optimization because we avoid the hardware access for the common case where no interrupt happens after we marked it disabled. If an interrupt happens, then the interrupt flow handler masks the line at the hardware level and marks it pending.

If the interrupt chip does not implement the irq_disable callback, a driver can disable the lazy approach for a particular irq line by calling ‘irq_set_status_flags(irq, IRQ_DISABLE_UNLAZY)’. This can be used for devices which cannot disable the interrupt at the device level under certain circumstances and have to use disable_irq[_nosync] instead.

void handle_simple_irq(struct irq_desc * desc)

Simple and software-decoded IRQs.

Parameters

struct irq_desc * desc
the interrupt description structure for this irq

Description

Simple interrupts are either sent from a demultiplexing interrupt handler or come from hardware, where no interrupt hardware control is necessary.

Note

The caller is expected to handle the ack, clear, mask and
unmask issues if necessary.
void handle_untracked_irq(struct irq_desc * desc)

Simple and software-decoded IRQs.

Parameters

struct irq_desc * desc
the interrupt description structure for this irq

Description

Untracked interrupts are sent from a demultiplexing interrupt handler when the demultiplexer does not know which device it its multiplexed irq domain generated the interrupt. IRQ’s handled through here are not subjected to stats tracking, randomness, or spurious interrupt detection.

Note

Like handle_simple_irq, the caller is expected to handle
the ack, clear, mask and unmask issues if necessary.
void handle_level_irq(struct irq_desc * desc)

Level type irq handler

Parameters

struct irq_desc * desc
the interrupt description structure for this irq

Description

Level type interrupts are active as long as the hardware line has the active level. This may require to mask the interrupt and unmask it after the associated handler has acknowledged the device, so the interrupt line is back to inactive.
void handle_fasteoi_irq(struct irq_desc * desc)

irq handler for transparent controllers

Parameters

struct irq_desc * desc
the interrupt description structure for this irq

Description

Only a single callback will be issued to the chip: an ->:c:func:eoi() call when the interrupt has been serviced. This enables support for modern forms of interrupt handlers, which handle the flow details in hardware, transparently.
void handle_edge_irq(struct irq_desc * desc)

edge type IRQ handler

Parameters

struct irq_desc * desc
the interrupt description structure for this irq

Description

Interrupt occures on the falling and/or rising edge of a hardware signal. The occurrence is latched into the irq controller hardware and must be acked in order to be reenabled. After the ack another interrupt can happen on the same source even before the first one is handled by the associated event handler. If this happens it might be necessary to disable (mask) the interrupt depending on the controller hardware. This requires to reenable the interrupt inside of the loop which handles the interrupts which have arrived while the handler was running. If all pending interrupts are handled, the loop is left.
void handle_edge_eoi_irq(struct irq_desc * desc)

edge eoi type IRQ handler

Parameters

struct irq_desc * desc
the interrupt description structure for this irq

Description

Similar as the above handle_edge_irq, but using eoi and w/o the mask/unmask logic.

void handle_percpu_irq(struct irq_desc * desc)

Per CPU local irq handler

Parameters

struct irq_desc * desc
the interrupt description structure for this irq

Description

Per CPU interrupts on SMP machines without locking requirements
void handle_percpu_devid_irq(struct irq_desc * desc)

Per CPU local irq handler with per cpu dev ids

Parameters

struct irq_desc * desc
the interrupt description structure for this irq

Description

Per CPU interrupts on SMP machines without locking requirements. Same as handle_percpu_irq() above but with the following extras:

action->percpu_dev_id is a pointer to percpu variables which contain the real device id for the cpu on which this handler is called

void irq_cpu_online(void)

Invoke all irq_cpu_online functions.

Parameters

void
no arguments

Description

Iterate through all irqs and invoke the chip.:c:func:irq_cpu_online() for each.
void irq_cpu_offline(void)

Invoke all irq_cpu_offline functions.

Parameters

void
no arguments

Description

Iterate through all irqs and invoke the chip.:c:func:irq_cpu_offline() for each.
void irq_chip_enable_parent(struct irq_data * data)

Enable the parent interrupt (defaults to unmask if NULL)

Parameters

struct irq_data * data
Pointer to interrupt specific data
void irq_chip_disable_parent(struct irq_data * data)

Disable the parent interrupt (defaults to mask if NULL)

Parameters

struct irq_data * data
Pointer to interrupt specific data
void irq_chip_ack_parent(struct irq_data * data)

Acknowledge the parent interrupt

Parameters

struct irq_data * data
Pointer to interrupt specific data
void irq_chip_mask_parent(struct irq_data * data)

Mask the parent interrupt

Parameters

struct irq_data * data
Pointer to interrupt specific data
void irq_chip_unmask_parent(struct irq_data * data)

Unmask the parent interrupt

Parameters

struct irq_data * data
Pointer to interrupt specific data
void irq_chip_eoi_parent(struct irq_data * data)

Invoke EOI on the parent interrupt

Parameters

struct irq_data * data
Pointer to interrupt specific data
int irq_chip_set_affinity_parent(struct irq_data * data, const struct cpumask * dest, bool force)

Set affinity on the parent interrupt

Parameters

struct irq_data * data
Pointer to interrupt specific data
const struct cpumask * dest
The affinity mask to set
bool force
Flag to enforce setting (disable online checks)

Description

Conditinal, as the underlying parent chip might not implement it.

int irq_chip_set_type_parent(struct irq_data * data, unsigned int type)

Set IRQ type on the parent interrupt

Parameters

struct irq_data * data
Pointer to interrupt specific data
unsigned int type
IRQ_TYPE_{LEVEL,EDGE}_* value - see include/linux/irq.h

Description

Conditional, as the underlying parent chip might not implement it.

int irq_chip_retrigger_hierarchy(struct irq_data * data)

Retrigger an interrupt in hardware

Parameters

struct irq_data * data
Pointer to interrupt specific data

Description

Iterate through the domain hierarchy of the interrupt and check whether a hw retrigger function exists. If yes, invoke it.

int irq_chip_set_vcpu_affinity_parent(struct irq_data * data, void * vcpu_info)

Set vcpu affinity on the parent interrupt

Parameters

struct irq_data * data
Pointer to interrupt specific data
void * vcpu_info
The vcpu affinity information
int irq_chip_set_wake_parent(struct irq_data * data, unsigned int on)

Set/reset wake-up on the parent interrupt

Parameters

struct irq_data * data
Pointer to interrupt specific data
unsigned int on
Whether to set or reset the wake-up capability of this irq

Description

Conditional, as the underlying parent chip might not implement it.

int irq_chip_compose_msi_msg(struct irq_data * data, struct msi_msg * msg)

Componse msi message for a irq chip

Parameters

struct irq_data * data
Pointer to interrupt specific data
struct msi_msg * msg
Pointer to the MSI message

Description

For hierarchical domains we find the first chip in the hierarchy which implements the irq_compose_msi_msg callback. For non hierarchical we use the top level chip.

int irq_chip_pm_get(struct irq_data * data)

Enable power for an IRQ chip

Parameters

struct irq_data * data
Pointer to interrupt specific data

Description

Enable the power to the IRQ chip referenced by the interrupt data structure.

int irq_chip_pm_put(struct irq_data * data)

Disable power for an IRQ chip

Parameters

struct irq_data * data
Pointer to interrupt specific data

Description

Disable the power to the IRQ chip referenced by the interrupt data structure, belongs. Note that power will only be disabled, once this function has been called for all IRQs that have called irq_chip_pm_get().

Credits

The following people have contributed to this document:

  1. Thomas Gleixner tglx@linutronix.de
  2. Ingo Molnar mingo@elte.hu