Input Subsystem¶

Input core¶

struct input_value¶: input value representation

Definition:

struct input_value {
    __u16 type;
    __u16 code;
    __s32 value;
};

Members

type: type of value (EV_KEY, EV_ABS, etc)
code: the value code
value: the value

struct input_dev¶: represents an input device

Definition:

struct input_dev {
    const char *name;
    const char *phys;
    const char *uniq;
    struct input_id id;
    unsigned long propbit[BITS_TO_LONGS(INPUT_PROP_CNT)];
    unsigned long evbit[BITS_TO_LONGS(EV_CNT)];
    unsigned long keybit[BITS_TO_LONGS(KEY_CNT)];
    unsigned long relbit[BITS_TO_LONGS(REL_CNT)];
    unsigned long absbit[BITS_TO_LONGS(ABS_CNT)];
    unsigned long mscbit[BITS_TO_LONGS(MSC_CNT)];
    unsigned long ledbit[BITS_TO_LONGS(LED_CNT)];
    unsigned long sndbit[BITS_TO_LONGS(SND_CNT)];
    unsigned long ffbit[BITS_TO_LONGS(FF_CNT)];
    unsigned long swbit[BITS_TO_LONGS(SW_CNT)];
    unsigned int hint_events_per_packet;
    unsigned int keycodemax;
    unsigned int keycodesize;
    void *keycode;
    int (*setkeycode)(struct input_dev *dev,const struct input_keymap_entry *ke, unsigned int *old_keycode);
    int (*getkeycode)(struct input_dev *dev, struct input_keymap_entry *ke);
    struct ff_device *ff;
    struct input_dev_poller *poller;
    unsigned int repeat_key;
    struct timer_list timer;
    int rep[REP_CNT];
    struct input_mt *mt;
    struct input_absinfo *absinfo;
    unsigned long key[BITS_TO_LONGS(KEY_CNT)];
    unsigned long led[BITS_TO_LONGS(LED_CNT)];
    unsigned long snd[BITS_TO_LONGS(SND_CNT)];
    unsigned long sw[BITS_TO_LONGS(SW_CNT)];
    int (*open)(struct input_dev *dev);
    void (*close)(struct input_dev *dev);
    int (*flush)(struct input_dev *dev, struct file *file);
    int (*event)(struct input_dev *dev, unsigned int type, unsigned int code, int value);
    struct input_handle __rcu *grab;
    spinlock_t event_lock;
    struct mutex mutex;
    unsigned int users;
    bool going_away;
    struct device dev;
    struct list_head        h_list;
    struct list_head        node;
    unsigned int num_vals;
    unsigned int max_vals;
    struct input_value *vals;
    bool devres_managed;
    ktime_t timestamp[INPUT_CLK_MAX];
    bool inhibited;
};

Members

name: name of the device
phys: physical path to the device in the system hierarchy
uniq: unique identification code for the device (if device has it)
id: id of the device (struct input_id)
propbit: bitmap of device properties and quirks
evbit: bitmap of types of events supported by the device (EV_KEY, EV_REL, etc.)
keybit: bitmap of keys/buttons this device has
relbit: bitmap of relative axes for the device
absbit: bitmap of absolute axes for the device
mscbit: bitmap of miscellaneous events supported by the device
ledbit: bitmap of leds present on the device
sndbit: bitmap of sound effects supported by the device
ffbit: bitmap of force feedback effects supported by the device
swbit: bitmap of switches present on the device
hint_events_per_packet: average number of events generated by the device in a packet (between EV_SYN/SYN_REPORT events). Used by event handlers to estimate size of the buffer needed to hold events.
keycodemax: size of keycode table
keycodesize: size of elements in keycode table
keycode: map of scancodes to keycodes for this device
setkeycode: optional method to alter current keymap, used to implement sparse keymaps. If not supplied default mechanism will be used. The method is being called while holding event_lock and thus must not sleep
getkeycode: optional legacy method to retrieve current keymap.
ff: force feedback structure associated with the device if device supports force feedback effects
poller: poller structure associated with the device if device is set up to use polling mode
repeat_key: stores key code of the last key pressed; used to implement software autorepeat
timer: timer for software autorepeat
rep: current values for autorepeat parameters (delay, rate)
mt: pointer to multitouch state
absinfo: array of struct input_absinfo elements holding information about absolute axes (current value, min, max, flat, fuzz, resolution)
key: reflects current state of device’s keys/buttons
led: reflects current state of device’s LEDs
snd: reflects current state of sound effects
sw: reflects current state of device’s switches
open: this method is called when the very first user calls input_open_device(). The driver must prepare the device to start generating events (start polling thread, request an IRQ, submit URB, etc.). The meaning of open() is to start providing events to the input core.
close: this method is called when the very last user calls input_close_device(). The meaning of close() is to stop providing events to the input core.
flush: purges the device. Most commonly used to get rid of force feedback effects loaded into the device when disconnecting from it
event: event handler for events sent _to_ the device, like EV_LED or EV_SND. The device is expected to carry out the requested action (turn on a LED, play sound, etc.) The call is protected by event_lock and must not sleep
grab: input handle that currently has the device grabbed (via EVIOCGRAB ioctl). When a handle grabs a device it becomes sole recipient for all input events coming from the device
event_lock: this spinlock is taken when input core receives and processes a new event for the device (in input_event()). Code that accesses and/or modifies parameters of a device (such as keymap or absmin, absmax, absfuzz, etc.) after device has been registered with input core must take this lock.
mutex: serializes calls to open(), close() and flush() methods
users: stores number of users (input handlers) that opened this device. It is used by input_open_device() and input_close_device() to make sure that dev->open() is only called when the first user opens device and dev->close() is called when the very last user closes the device
going_away: marks devices that are in a middle of unregistering and causes input_open_device*() fail with -ENODEV.
dev: driver model’s view of this device
h_list: list of input handles associated with the device. When accessing the list dev->mutex must be held
node: used to place the device onto input_dev_list
num_vals: number of values queued in the current frame
max_vals: maximum number of values queued in a frame
vals: array of values queued in the current frame
devres_managed: indicates that devices is managed with devres framework and needs not be explicitly unregistered or freed.
timestamp: storage for a timestamp set by input_set_timestamp called by a driver
inhibited: indicates that the input device is inhibited. If that is the case then input core ignores any events generated by the device. Device’s close() is called when it is being inhibited and its open() is called when it is being uninhibited.

struct input_handler¶: implements one of interfaces for input devices

Definition:

struct input_handler {
    void *private;
    void (*event)(struct input_handle *handle, unsigned int type, unsigned int code, int value);
    unsigned int (*events)(struct input_handle *handle, struct input_value *vals, unsigned int count);
    bool (*filter)(struct input_handle *handle, unsigned int type, unsigned int code, int value);
    bool (*match)(struct input_handler *handler, struct input_dev *dev);
    int (*connect)(struct input_handler *handler, struct input_dev *dev, const struct input_device_id *id);
    void (*disconnect)(struct input_handle *handle);
    void (*start)(struct input_handle *handle);
    bool passive_observer;
    bool legacy_minors;
    int minor;
    const char *name;
    const struct input_device_id *id_table;
    struct list_head        h_list;
    struct list_head        node;
};

Members

private: driver-specific data
event: event handler. This method is being called by input core with interrupts disabled and dev->event_lock spinlock held and so it may not sleep
events: event sequence handler. This method is being called by input core with interrupts disabled and dev->event_lock spinlock held and so it may not sleep. The method must return number of events passed to it.
filter: similar to event; separates normal event handlers from “filters”.
match: called after comparing device’s id with handler’s id_table to perform fine-grained matching between device and handler
connect: called when attaching a handler to an input device
disconnect: disconnects a handler from input device
start: starts handler for given handle. This function is called by input core right after connect() method and also when a process that “grabbed” a device releases it
passive_observer: set to true by drivers only interested in observing data stream from devices if there are other users present. Such drivers will not result in starting underlying hardware device when input_open_device() is called for their handles
legacy_minors: set to true by drivers using legacy minor ranges
minor: beginning of range of 32 legacy minors for devices this driver can provide
name: name of the handler, to be shown in /proc/bus/input/handlers
id_table: pointer to a table of input_device_ids this driver can handle
h_list: list of input handles associated with the handler
node: for placing the driver onto input_handler_list

Description

Input handlers attach to input devices and create input handles. There are likely several handlers attached to any given input device at the same time. All of them will get their copy of input event generated by the device.

The very same structure is used to implement input filters. Input core allows filters to run first and will not pass event to regular handlers if any of the filters indicate that the event should be filtered (by returning true from their filter() method).

Note that input core serializes calls to connect() and disconnect() methods.

struct input_handle¶: links input device with an input handler

Definition:

struct input_handle {
    void *private;
    int open;
    const char *name;
    struct input_dev *dev;
    struct input_handler *handler;
    unsigned int (*handle_events)(struct input_handle *handle,struct input_value *vals, unsigned int count);
    struct list_head        d_node;
    struct list_head        h_node;
};

Members

private: handler-specific data
open: counter showing whether the handle is ‘open’, i.e. should deliver events from its device
name: name given to the handle by handler that created it
dev: input device the handle is attached to
handler: handler that works with the device through this handle
handle_events: event sequence handler. It is set up by the input core according to event handling method specified in the handler. See input_handle_setup_event_handler(). This method is being called by the input core with interrupts disabled and dev->event_lock spinlock held and so it may not sleep.
d_node: used to put the handle on device’s list of attached handles
h_node: used to put the handle on handler’s list of handles from which it gets events

void input_set_events_per_packet(struct input_dev *dev, int n_events)¶: tell handlers about the driver event rate

Parameters

struct input_dev *dev: the input device used by the driver
int n_events: the average number of events between calls to input_sync()

Description

If the event rate sent from a device is unusually large, use this function to set the expected event rate. This will allow handlers to set up an appropriate buffer size for the event stream, in order to minimize information loss.

struct ff_device¶: force-feedback part of an input device

Definition:

struct ff_device {
    int (*upload)(struct input_dev *dev, struct ff_effect *effect, struct ff_effect *old);
    int (*erase)(struct input_dev *dev, int effect_id);
    int (*playback)(struct input_dev *dev, int effect_id, int value);
    void (*set_gain)(struct input_dev *dev, u16 gain);
    void (*set_autocenter)(struct input_dev *dev, u16 magnitude);
    void (*destroy)(struct ff_device *);
    void *private;
    unsigned long ffbit[BITS_TO_LONGS(FF_CNT)];
    struct mutex mutex;
    int max_effects;
    struct ff_effect *effects;
    struct file *effect_owners[] ;
};

Members

upload: Called to upload an new effect into device
erase: Called to erase an effect from device
playback: Called to request device to start playing specified effect
set_gain: Called to set specified gain
set_autocenter: Called to auto-center device
destroy: called by input core when parent input device is being destroyed
private: driver-specific data, will be freed automatically
ffbit: bitmap of force feedback capabilities truly supported by device (not emulated like ones in input_dev->ffbit)
mutex: mutex for serializing access to the device
max_effects: maximum number of effects supported by device
effects: pointer to an array of effects currently loaded into device
effect_owners: array of effect owners; when file handle owning an effect gets closed the effect is automatically erased

Description

Every force-feedback device must implement upload() and playback() methods; erase() is optional. set_gain() and set_autocenter() need only be implemented if driver sets up FF_GAIN and FF_AUTOCENTER bits.

Note that playback(), set_gain() and set_autocenter() are called with dev->event_lock spinlock held and interrupts off and thus may not sleep.

void input_event(struct input_dev *dev, unsigned int type, unsigned int code, int value)¶: report new input event

Parameters

struct input_dev *dev: device that generated the event
unsigned int type: type of the event
unsigned int code: event code
int value: value of the event

Description

This function should be used by drivers implementing various input devices to report input events. See also input_inject_event().

NOTE

input_event() may be safely used right after input device was allocated with input_allocate_device(), even before it is registered with input_register_device(), but the event will not reach any of the input handlers. Such early invocation of input_event() may be used to ‘seed’ initial state of a switch or initial position of absolute axis, etc.

void input_inject_event(struct input_handle *handle, unsigned int type, unsigned int code, int value)¶: send input event from input handler

Parameters

struct input_handle *handle: input handle to send event through
unsigned int type: type of the event
unsigned int code: event code
int value: value of the event

Description

Similar to input_event() but will ignore event if device is “grabbed” and handle injecting event is not the one that owns the device.

void input_alloc_absinfo(struct input_dev *dev)¶: allocates array of input_absinfo structs

Parameters

struct input_dev *dev: the input device emitting absolute events

Description

If the absinfo struct the caller asked for is already allocated, this functions will not do anything.

void input_copy_abs(struct input_dev *dst, unsigned int dst_axis, const struct input_dev *src, unsigned int src_axis)¶: Copy absinfo from one input_dev to another

Parameters

struct input_dev *dst: Destination input device to copy the abs settings to
unsigned int dst_axis: ABS_* value selecting the destination axis
const struct input_dev *src: Source input device to copy the abs settings from
unsigned int src_axis: ABS_* value selecting the source axis

Description

Set absinfo for the selected destination axis by copying it from the specified source input device’s source axis. This is useful to e.g. setup a pen/stylus input-device for combined touchscreen/pen hardware where the pen uses the same coordinates as the touchscreen.

int input_grab_device(struct input_handle *handle)¶: grabs device for exclusive use

Parameters

struct input_handle *handle: input handle that wants to own the device

Description

When a device is grabbed by an input handle all events generated by the device are delivered only to this handle. Also events injected by other input handles are ignored while device is grabbed.

void input_release_device(struct input_handle *handle)¶: release previously grabbed device

Parameters

struct input_handle *handle: input handle that owns the device

Description

Releases previously grabbed device so that other input handles can start receiving input events. Upon release all handlers attached to the device have their start() method called so they have a change to synchronize device state with the rest of the system.

int input_open_device(struct input_handle *handle)¶: open input device

Parameters

struct input_handle *handle: handle through which device is being accessed

Description

This function should be called by input handlers when they want to start receive events from given input device.

void input_close_device(struct input_handle *handle)¶: close input device

Parameters

struct input_handle *handle: handle through which device is being accessed

Description

This function should be called by input handlers when they want to stop receive events from given input device.

int input_scancode_to_scalar(const struct input_keymap_entry *ke, unsigned int *scancode)¶: converts scancode in struct input_keymap_entry

Parameters

const struct input_keymap_entry *ke: keymap entry containing scancode to be converted.
unsigned int *scancode: pointer to the location where converted scancode should be stored.

Description

This function is used to convert scancode stored in struct keymap_entry into scalar form understood by legacy keymap handling methods. These methods expect scancodes to be represented as ‘unsigned int’.

int input_get_keycode(struct input_dev *dev, struct input_keymap_entry *ke)¶: retrieve keycode currently mapped to a given scancode

Parameters

struct input_dev *dev: input device which keymap is being queried
struct input_keymap_entry *ke: keymap entry

Description

This function should be called by anyone interested in retrieving current keymap. Presently evdev handlers use it.

int input_set_keycode(struct input_dev *dev, const struct input_keymap_entry *ke)¶: attribute a keycode to a given scancode

Parameters

struct input_dev *dev: input device which keymap is being updated
const struct input_keymap_entry *ke: new keymap entry

Description

This function should be called by anyone needing to update current keymap. Presently keyboard and evdev handlers use it.

void input_reset_device(struct input_dev *dev)¶: reset/restore the state of input device

Parameters

struct input_dev *dev: input device whose state needs to be reset

Description

This function tries to reset the state of an opened input device and bring internal state and state if the hardware in sync with each other. We mark all keys as released, restore LED state, repeat rate, etc.

struct input_dev *input_allocate_device(void)¶: allocate memory for new input device

Parameters

void: no arguments

Description

Returns prepared struct input_dev or NULL.

NOTE

Use input_free_device() to free devices that have not been registered; input_unregister_device() should be used for already registered devices.

struct input_dev *devm_input_allocate_device(struct device *dev)¶: allocate managed input device

Parameters

struct device *dev: device owning the input device being created

Description

Returns prepared struct input_dev or NULL.

Managed input devices do not need to be explicitly unregistered or freed as it will be done automatically when owner device unbinds from its driver (or binding fails). Once managed input device is allocated, it is ready to be set up and registered in the same fashion as regular input device. There are no special devm_input_device_[un]register() variants, regular ones work with both managed and unmanaged devices, should you need them. In most cases however, managed input device need not be explicitly unregistered or freed.

NOTE

the owner device is set up as parent of input device and users should not override it.

void input_free_device(struct input_dev *dev)¶: free memory occupied by input_dev structure

Parameters

struct input_dev *dev: input device to free

Description

This function should only be used if input_register_device() was not called yet or if it failed. Once device was registered use input_unregister_device() and memory will be freed once last reference to the device is dropped.

Device should be allocated by input_allocate_device().

NOTE

If there are references to the input device then memory will not be freed until last reference is dropped.

void input_set_timestamp(struct input_dev *dev, ktime_t timestamp)¶: set timestamp for input events

Parameters

struct input_dev *dev: input device to set timestamp for
ktime_t timestamp: the time at which the event has occurred in CLOCK_MONOTONIC

Description

This function is intended to provide to the input system a more accurate time of when an event actually occurred. The driver should call this function as soon as a timestamp is acquired ensuring clock conversions in input_set_timestamp are done correctly.

The system entering suspend state between timestamp acquisition and calling input_set_timestamp can result in inaccurate conversions.

ktime_t *input_get_timestamp(struct input_dev *dev)¶: get timestamp for input events

Parameters

struct input_dev *dev: input device to get timestamp from

Description

A valid timestamp is a timestamp of non-zero value.

void input_set_capability(struct input_dev *dev, unsigned int type, unsigned int code)¶: mark device as capable of a certain event

Parameters

struct input_dev *dev: device that is capable of emitting or accepting event
unsigned int type: type of the event (EV_KEY, EV_REL, etc...)
unsigned int code: event code

Description

In addition to setting up corresponding bit in appropriate capability bitmap the function also adjusts dev->evbit.

void input_enable_softrepeat(struct input_dev *dev, int delay, int period)¶: enable software autorepeat

Parameters

struct input_dev *dev: input device
int delay: repeat delay
int period: repeat period

Description

Enable software autorepeat on the input device.

int input_register_device(struct input_dev *dev)¶: register device with input core

Parameters

struct input_dev *dev: device to be registered

Description

This function registers device with input core. The device must be allocated with input_allocate_device() and all it’s capabilities set up before registering. If function fails the device must be freed with input_free_device(). Once device has been successfully registered it can be unregistered with input_unregister_device(); input_free_device() should not be called in this case.

Note that this function is also used to register managed input devices (ones allocated with devm_input_allocate_device()). Such managed input devices need not be explicitly unregistered or freed, their tear down is controlled by the devres infrastructure. It is also worth noting that tear down of managed input devices is internally a 2-step process: registered managed input device is first unregistered, but stays in memory and can still handle input_event() calls (although events will not be delivered anywhere). The freeing of managed input device will happen later, when devres stack is unwound to the point where device allocation was made.

void input_unregister_device(struct input_dev *dev)¶: unregister previously registered device

Parameters

struct input_dev *dev: device to be unregistered

Description

This function unregisters an input device. Once device is unregistered the caller should not try to access it as it may get freed at any moment.

int input_register_handler(struct input_handler *handler)¶: register a new input handler

Parameters

struct input_handler *handler: handler to be registered

Description

This function registers a new input handler (interface) for input devices in the system and attaches it to all input devices that are compatible with the handler.

void input_unregister_handler(struct input_handler *handler)¶: unregisters an input handler

Parameters

struct input_handler *handler: handler to be unregistered

Description

This function disconnects a handler from its input devices and removes it from lists of known handlers.

int input_handler_for_each_handle(struct input_handler *handler, void *data, int (*fn)(struct input_handle*, void*))¶: handle iterator

Parameters

struct input_handler *handler: input handler to iterate
void *data: data for the callback
int (*fn)(struct input_handle *, void *): function to be called for each handle

Description

Iterate over bus’s list of devices, and call fn for each, passing it data and stop when fn returns a non-zero value. The function is using RCU to traverse the list and therefore may be using in atomic contexts. The fn callback is invoked from RCU critical section and thus must not sleep.

int input_register_handle(struct input_handle *handle)¶: register a new input handle

Parameters

struct input_handle *handle: handle to register

Description

This function puts a new input handle onto device’s and handler’s lists so that events can flow through it once it is opened using input_open_device().

This function is supposed to be called from handler’s connect() method.

void input_unregister_handle(struct input_handle *handle)¶: unregister an input handle

Parameters

struct input_handle *handle: handle to unregister

Description

This function removes input handle from device’s and handler’s lists.

This function is supposed to be called from handler’s disconnect() method.

int input_get_new_minor(int legacy_base, unsigned int legacy_num, bool allow_dynamic)¶: allocates a new input minor number

Parameters

int legacy_base: beginning or the legacy range to be searched
unsigned int legacy_num: size of legacy range
bool allow_dynamic: whether we can also take ID from the dynamic range

Description

This function allocates a new device minor for from input major namespace. Caller can request legacy minor by specifying legacy_base and legacy_num parameters and whether ID can be allocated from dynamic range if there are no free IDs in legacy range.

void input_free_minor(unsigned int minor)¶: release previously allocated minor

Parameters

unsigned int minor: minor to be released

Description

This function releases previously allocated input minor so that it can be reused later.

int input_ff_upload(struct input_dev *dev, struct ff_effect *effect, struct file *file)¶: upload effect into force-feedback device

Parameters

struct input_dev *dev: input device
struct ff_effect *effect: effect to be uploaded
struct file *file: owner of the effect

int input_ff_erase(struct input_dev *dev, int effect_id, struct file *file)¶: erase a force-feedback effect from device

Parameters

struct input_dev *dev: input device to erase effect from
int effect_id: id of the effect to be erased
struct file *file: purported owner of the request

Description

This function erases a force-feedback effect from specified device. The effect will only be erased if it was uploaded through the same file handle that is requesting erase.

int input_ff_event(struct input_dev *dev, unsigned int type, unsigned int code, int value)¶: generic handler for force-feedback events

Parameters

struct input_dev *dev: input device to send the effect to
unsigned int type: event type (anything but EV_FF is ignored)
unsigned int code: event code
int value: event value

int input_ff_create(struct input_dev *dev, unsigned int max_effects)¶: create force-feedback device

Parameters

struct input_dev *dev: input device supporting force-feedback
unsigned int max_effects: maximum number of effects supported by the device

Description

This function allocates all necessary memory for a force feedback portion of an input device and installs all default handlers. dev->ffbit should be already set up before calling this function. Once ff device is created you need to setup its upload, erase, playback and other handlers before registering input device

void input_ff_destroy(struct input_dev *dev)¶: frees force feedback portion of input device

Parameters

struct input_dev *dev: input device supporting force feedback

Description

This function is only needed in error path as input core will automatically free force feedback structures when device is destroyed.

int input_ff_create_memless(struct input_dev *dev, void *data, int (*play_effect)(struct input_dev*, void*, struct ff_effect*))¶: create memoryless force-feedback device

Parameters

struct input_dev *dev: input device supporting force-feedback
void *data: driver-specific data to be passed into play_effect
int (*play_effect)(struct input_dev *, void *, struct ff_effect *): driver-specific method for playing FF effect

Multitouch Library¶

struct input_mt_slot¶: represents the state of an input MT slot

Definition:

struct input_mt_slot {
    int abs[ABS_MT_LAST - ABS_MT_FIRST + 1];
    unsigned int frame;
    unsigned int key;
};

Members

abs: holds current values of ABS_MT axes for this slot
frame: last frame at which input_mt_report_slot_state() was called
key: optional driver designation of this slot

struct input_mt¶: state of tracked contacts

Definition:

struct input_mt {
    int trkid;
    int num_slots;
    int slot;
    unsigned int flags;
    unsigned int frame;
    int *red;
    struct input_mt_slot slots[] ;
};

Members

trkid: stores MT tracking ID for the next contact
num_slots: number of MT slots the device uses
slot: MT slot currently being transmitted
flags: input_mt operation flags
frame: increases every time input_mt_sync_frame() is called
red: reduced cost matrix for in-kernel tracking
slots: array of slots holding current values of tracked contacts

struct input_mt_pos¶: contact position

Definition:

struct input_mt_pos {
    s16 x, y;
};

Members

x: horizontal coordinate
y: vertical coordinate

int input_mt_init_slots(struct input_dev *dev, unsigned int num_slots, unsigned int flags)¶: initialize MT input slots

Parameters

struct input_dev *dev: input device supporting MT events and finger tracking
unsigned int num_slots: number of slots used by the device
unsigned int flags: mt tasks to handle in core

Description

This function allocates all necessary memory for MT slot handling in the input device, prepares the ABS_MT_SLOT and ABS_MT_TRACKING_ID events for use and sets up appropriate buffers. Depending on the flags set, it also performs pointer emulation and frame synchronization.

May be called repeatedly. Returns -EINVAL if attempting to reinitialize with a different number of slots.

void input_mt_destroy_slots(struct input_dev *dev)¶: frees the MT slots of the input device

Parameters

struct input_dev *dev: input device with allocated MT slots

Description

This function is only needed in error path as the input core will automatically free the MT slots when the device is destroyed.

bool input_mt_report_slot_state(struct input_dev *dev, unsigned int tool_type, bool active)¶: report contact state

Parameters

struct input_dev *dev: input device with allocated MT slots
unsigned int tool_type: the tool type to use in this slot
bool active: true if contact is active, false otherwise

Description

Reports a contact via ABS_MT_TRACKING_ID, and optionally ABS_MT_TOOL_TYPE. If active is true and the slot is currently inactive, or if the tool type is changed, a new tracking id is assigned to the slot. The tool type is only reported if the corresponding absbit field is set.

Returns true if contact is active.

void input_mt_report_finger_count(struct input_dev *dev, int count)¶: report contact count

Parameters

struct input_dev *dev: input device with allocated MT slots
int count: the number of contacts

Description

Reports the contact count via BTN_TOOL_FINGER, BTN_TOOL_DOUBLETAP, BTN_TOOL_TRIPLETAP and BTN_TOOL_QUADTAP.

The input core ensures only the KEY events already setup for this device will produce output.

void input_mt_report_pointer_emulation(struct input_dev *dev, bool use_count)¶: common pointer emulation

Parameters

struct input_dev *dev: input device with allocated MT slots
bool use_count: report number of active contacts as finger count

Description

Performs legacy pointer emulation via BTN_TOUCH, ABS_X, ABS_Y and ABS_PRESSURE. Touchpad finger count is emulated if use_count is true.

The input core ensures only the KEY and ABS axes already setup for this device will produce output.

void input_mt_drop_unused(struct input_dev *dev)¶: Inactivate slots not seen in this frame

Parameters

struct input_dev *dev: input device with allocated MT slots

Description

Lift all slots not seen since the last call to this function.

void input_mt_sync_frame(struct input_dev *dev)¶: synchronize mt frame

Parameters

struct input_dev *dev: input device with allocated MT slots

Description

Close the frame and prepare the internal state for a new one. Depending on the flags, marks unused slots as inactive and performs pointer emulation.

int input_mt_assign_slots(struct input_dev *dev, int *slots, const struct input_mt_pos *pos, int num_pos, int dmax)¶: perform a best-match assignment

Parameters

struct input_dev *dev: input device with allocated MT slots
int *slots: the slot assignment to be filled
const struct input_mt_pos *pos: the position array to match
int num_pos: number of positions
int dmax: maximum ABS_MT_POSITION displacement (zero for infinite)

Description

Performs a best match against the current contacts and returns the slot assignment list. New contacts are assigned to unused slots.

The assignments are balanced so that all coordinate displacements are below the euclidian distance dmax. If no such assignment can be found, some contacts are assigned to unused slots.

Returns zero on success, or negative error in case of failure.

int input_mt_get_slot_by_key(struct input_dev *dev, int key)¶: return slot matching key

Parameters

struct input_dev *dev: input device with allocated MT slots
int key: the key of the sought slot

Description

Returns the slot of the given key, if it exists, otherwise set the key on the first unused slot and return.

If no available slot can be found, -1 is returned. Note that for this function to work properly, input_mt_sync_frame() has to be called at each frame.

Matrix keyboards/keypads¶

struct matrix_keymap_data¶: keymap for matrix keyboards

Definition:

struct matrix_keymap_data {
    const uint32_t *keymap;
    unsigned int    keymap_size;
};

Members

keymap: pointer to array of uint32 values encoded with KEY() macro representing keymap
keymap_size: number of entries (initialized) in this keymap

Description

This structure is supposed to be used by platform code to supply keymaps to drivers that implement matrix-like keypads/keyboards.

Sparse keymap support¶

struct key_entry¶: keymap entry for use in sparse keymap

Definition:

struct key_entry {
    int type;
    u32 code;
    union {
        u16 keycode;
        struct {
            u8 code;
            u8 value;
        } sw;
    };
};

Members

type: Type of the key entry (KE_KEY, KE_SW, KE_VSW, KE_END); drivers are allowed to extend the list with their own private definitions.
code: Device-specific data identifying the button/switch
{unnamed_union}: anonymous
keycode: KEY_* code assigned to a key/button
sw: struct with code/value used by KE_SW and KE_VSW
sw.code: SW_* code assigned to a switch
sw.value: Value that should be sent in an input even when KE_SW switch is toggled. KE_VSW switches ignore this field and expect driver to supply value for the event.

Description

This structure defines an entry in a sparse keymap used by some input devices for which traditional table-based approach is not suitable.

struct key_entry *sparse_keymap_entry_from_scancode(struct input_dev *dev, unsigned int code)¶: perform sparse keymap lookup

Parameters

struct input_dev *dev: Input device using sparse keymap
unsigned int code: Scan code

Description

This function is used to perform struct key_entry lookup in an input device using sparse keymap.

struct key_entry *sparse_keymap_entry_from_keycode(struct input_dev *dev, unsigned int keycode)¶: perform sparse keymap lookup

Parameters

struct input_dev *dev: Input device using sparse keymap
unsigned int keycode: Key code

Description

This function is used to perform struct key_entry lookup in an input device using sparse keymap.

int sparse_keymap_setup(struct input_dev *dev, const struct key_entry *keymap, int (*setup)(struct input_dev*, struct key_entry*))¶: set up sparse keymap for an input device

Parameters

struct input_dev *dev: Input device
const struct key_entry *keymap: Keymap in form of array of key_entry structures ending with KE_END type entry
int (*setup)(struct input_dev *, struct key_entry *): Function that can be used to adjust keymap entries depending on device’s needs, may be NULL

Description

The function calculates size and allocates copy of the original keymap after which sets up input device event bits appropriately. The allocated copy of the keymap is automatically freed when it is no longer needed.

void sparse_keymap_report_entry(struct input_dev *dev, const struct key_entry *ke, unsigned int value, bool autorelease)¶: report event corresponding to given key entry

Parameters

struct input_dev *dev: Input device for which event should be reported
const struct key_entry *ke: key entry describing event
unsigned int value: Value that should be reported (ignored by KE_SW entries)
bool autorelease: Signals whether release event should be emitted for KE_KEY entries right after reporting press event, ignored by all other entries

Description

This function is used to report input event described by given struct key_entry.

bool sparse_keymap_report_event(struct input_dev *dev, unsigned int code, unsigned int value, bool autorelease)¶: report event corresponding to given scancode

Parameters

struct input_dev *dev: Input device using sparse keymap
unsigned int code: Scan code
unsigned int value: Value that should be reported (ignored by KE_SW entries)
bool autorelease: Signals whether release event should be emitted for KE_KEY entries right after reporting press event, ignored by all other entries

Description

This function is used to perform lookup in an input device using sparse keymap and report corresponding event. Returns true if lookup was successful and false otherwise.

PS/2 protocol support¶

enum ps2_disposition¶: indicates how received byte should be handled

Constants

PS2_PROCESS: pass to the main protocol handler, process normally
PS2_IGNORE: skip the byte
PS2_ERROR: do not process the byte, abort command in progress

struct ps2dev¶: represents a device using PS/2 protocol

Definition:

struct ps2dev {
    struct serio *serio;
    struct mutex cmd_mutex;
    wait_queue_head_t wait;
    unsigned long flags;
    u8 cmdbuf[8];
    u8 cmdcnt;
    u8 nak;
    ps2_pre_receive_handler_t pre_receive_handler;
    ps2_receive_handler_t receive_handler;
};

Members

serio: a serio port used by the PS/2 device
cmd_mutex: a mutex ensuring that only one command is executing at a time
wait: a waitqueue used to signal completion from the serio interrupt handler
flags: various internal flags indicating stages of PS/2 command execution
cmdbuf: buffer holding command response
cmdcnt: outstanding number of bytes of the command response
nak: a byte transmitted by the device when it refuses command
pre_receive_handler: checks communication errors and returns disposition (enum ps2_disposition) of the received data byte
receive_handler: main handler of particular PS/2 protocol, such as keyboard or mouse protocol

int ps2_sendbyte(struct ps2dev *ps2dev, u8 byte, unsigned int timeout)¶: sends a byte to the device and wait for acknowledgement

Parameters

struct ps2dev *ps2dev: a PS/2 device to send the data to
u8 byte: data to be sent to the device
unsigned int timeout: timeout for sending the data and receiving an acknowledge

Description

The function doesn’t handle retransmission, the caller is expected to handle it when needed.

ps2_sendbyte() can only be called from a process context.

void ps2_begin_command(struct ps2dev *ps2dev)¶: mark beginning of execution of a complex command

Parameters

struct ps2dev *ps2dev: a PS/2 device executing the command

Description

Serializes a complex/compound command. Once command is finished ps2_end_command() should be called.

void ps2_end_command(struct ps2dev *ps2dev)¶: mark end of execution of a complex command

Parameters

struct ps2dev *ps2dev: a PS/2 device executing the command

void ps2_drain(struct ps2dev *ps2dev, size_t maxbytes, unsigned int timeout)¶: waits for device to transmit requested number of bytes and discards them

Parameters

struct ps2dev *ps2dev: the PS/2 device that should be drained
size_t maxbytes: maximum number of bytes to be drained
unsigned int timeout: time to drain the device

bool ps2_is_keyboard_id(u8 id_byte)¶: checks received ID byte against the list of known keyboard IDs

Parameters

u8 id_byte: data byte that should be checked

int __ps2_command(struct ps2dev *ps2dev, u8 *param, unsigned int command)¶: send a command to PS/2 device

Parameters

struct ps2dev *ps2dev: the PS/2 device that should execute the command
u8 *param: a buffer containing parameters to be sent along with the command, or place where the results of the command execution will be deposited, or both
unsigned int command: command word that encodes the command itself, as well as number of additional parameter bytes that should be sent to the device and expected length of the command response

Description

Not serialized. Callers should use ps2_begin_command() and ps2_end_command() to ensure proper serialization for complex commands.

int ps2_command(struct ps2dev *ps2dev, u8 *param, unsigned int command)¶: send a command to PS/2 device

Parameters

struct ps2dev *ps2dev: the PS/2 device that should execute the command
u8 *param: a buffer containing parameters to be sent along with the command, or place where the results of the command execution will be deposited, or both
unsigned int command: command word that encodes the command itself, as well as number of additional parameter bytes that should be sent to the device and expected length of the command response

Note

ps2_command() serializes the command execution so that only one command can be executed at a time for either individual port or the entire 8042 controller.

int ps2_sliced_command(struct ps2dev *ps2dev, u8 command)¶: sends an extended PS/2 command to a mouse

Parameters

struct ps2dev *ps2dev: the PS/2 device that should execute the command
u8 command: command byte

Description

The command is sent using “sliced” syntax understood by advanced devices, such as Logitech or Synaptics touchpads. The command is encoded as: 0xE6 0xE8 rr 0xE8 ss 0xE8 tt 0xE8 uu where (rr*64)+(ss*16)+(tt*4)+uu is the command.

void ps2_init(struct ps2dev *ps2dev, struct serio *serio, ps2_pre_receive_handler_t pre_receive_handler, ps2_receive_handler_t receive_handler)¶: initializes ps2dev structure

Parameters

struct ps2dev *ps2dev: structure to be initialized
struct serio *serio: serio port associated with the PS/2 device
ps2_pre_receive_handler_t pre_receive_handler: validation handler to check basic communication state
ps2_receive_handler_t receive_handler: main protocol handler

Description

Prepares ps2dev structure for use in drivers for PS/2 devices.

irqreturn_t ps2_interrupt(struct serio *serio, u8 data, unsigned int flags)¶: common interrupt handler for PS/2 devices

Parameters

struct serio *serio: serio port for the device
u8 data: a data byte received from the device
unsigned int flags: flags such as SERIO_PARITY or SERIO_TIMEOUT indicating state of the data transfer

Description

ps2_interrupt() invokes pre-receive handler, optionally handles command acknowledgement and response from the device, and finally passes the data to the main protocol handler for future processing.