path: root/libgamepad.h

/* See LICENSE file for copyright and license details. */
#ifndef LIBGAMEPAD_H
#define LIBGAMEPAD_H

#include <linux/input.h>
#include <sys/ioctl.h>
#include <errno.h>
#include <fcntl.h>
#include <stdint.h>
#include <stddef.h>
#include <string.h>
#include <time.h>
#include <unistd.h>

#include <libevdev/libevdev.h>


/**
 * Opaque structure for monitoring device attachment changes
 */
typedef struct libgamepad_attachment_monitor LIBGAMEPAD_ATTACHMENT_MONITOR;


/**
 * Device attachment event type
 */
enum libgamepad_attachment_event_type {
	/**
	 * Device has been added
	 */
	LIBGAMEPAD_ADDED,

	/**
	 * Device has been removed
	 */
	LIBGAMEPAD_REMOVED
};


/**
 * Device type
 *
 * A device can have any number of these applied to
 * it, it may also have unknown types beyond these
 */
enum libgamepad_type {
	/**
	 * Gamepad, joystick, steering wheel, or similar
	 */
	LIBGAMEPAD_GAMEPAD = 0x0001,

	/**
	 * Computer mouse
	 */
	LIBGAMEPAD_MOUSE = 0x0002
};


/**
 * Gamepad input type
 */
enum libgamepad_input_type {
	/**
	 * Button/key
	 */
	LIBGAMEPAD_BUTTON,

	/**
	 * Absolute axis
	 */
	LIBGAMEPAD_ABSOLUTE_AXIS,

	/**
	 * Relative axis
	 */
	LIBGAMEPAD_RELATIVE_AXIS
};


/**
 * Subdevice input event structure
 */
struct libgamepad_input_event {
	/**
	 * The affect input type
	 */
	enum libgamepad_input_type type;

	/**
	 * Whether the event was polled in a
	 * synchronisation read
	 */
	short int sync_event;

	/**
	 * The button/key or axis affect by the event
	 */
	uint16_t code;

	/**
	 * The new value on the button/key or axis,
	 * or the delta if on a relative axis
	 */
	int32_t value;

	/**
	 * Event timestamp
	 */
	struct timeval time;
};


/**
 * Subdevice on a device
 * 
 * For example a modern gamepad may be split into
 * a gamepad, computer mouse, and motion sensor
 *
 * Structure is always deallocated by the library
 * using free(3)
 */
struct libgamepad_subdevice {
	/**
	 * Device type
	 */
	enum libgamepad_type type;

	/**
	 * Device path
	 */
	char path[];
};


/**
 * Physical device
 * 
 * Contents of structure is deallocated with
 * `libgamepad_close_superdevice`
 */
struct libgamepad_superdevice {
	/**
	 * Device path in /sys
	 */
	char *syspath;

	/**
	 * Number of subdevices
	 */
	size_t ndevices;

	/**
	 * Subdevices
	 */
	struct libgamepad_subdevice **devices;

	/**
	 * Number of LEDs
	 */
	size_t nleds;

	/**
	 * Paths to LEDs
	 */
	char **leds;

	/**
	 * Number of power supplies (batteries)
	 */
	size_t npower_supplies;

	/**
	 * Paths of power supplies (batteries)
	 */
	char **power_supplies;
};


/**
 * Subdevice structure for detailed information listening on input events
 */
struct libgamepad_device {
	/**
	 * File descriptor to the device, the application
	 * may use it to poll for read-readyness
	 */
	int fd;

	/**
	 * Bus type the device is connect via, see BUS_-prefixed
	 * constants in <linux/input.h>
	 */
	unsigned int bus_type;

	/**
	 * Vendor ID for the device (sub- or superdevice)
	 */
	unsigned int vendor;

	/**
	 * Product ID for the device (sub- or superdevice)
	 */
	unsigned int product;

	/**
	 * Product version ID for the device (sub- or superdevice)
	 */
	unsigned int version;

	/**
	 * FOR INTERNAL USE
	 * 
	 * Specifies whether `.fd` shall be closed with the device
	 */
	int close_fd;

	/**
	 * FOR INTERNAL USE
	 * 
	 * Whether the device must be synchronised
	 */
	int require_sync;

	/**
	 * Human-readable device (sub- or superdevice) name
	 */
	const char *name;

	/**
	 * ID that is supposted to be unique to the device
	 * (sub- or superdevice)
	 */
	const char *unique_id;

	/**
	 * The location if the device
	 */
	const char *physical_location;

	/**
	 * libevdev instance for the device
	 */
	struct libevdev *dev;

	/**
	 * Number of (digital) buttons/keys present
	 * on the device
	 */
	size_t nbuttons;

	/**
	 * Number of absolute axes present on the device
	 */
	size_t nabsolute_axes;

	/**
	 * Number of relative axes present on the device
	 */
	size_t nrelative_axes;

	/**
	 * Map from button/key indices to button/key codes
	 */
	uint16_t *buttons;

	/**
	 * Map from absolute axis indices to absolute axis codes
	 */
	uint16_t *absolute_axes;

	/**
	 * Map from relative axis indices to relative axis codes
	 */
	uint16_t *relative_axes;

	/**
	 * Maps from button/key codes to button indices,
	 * non-present buttons/keys map to -1, other
	 * values are in [0, `.nbuttons`[.
	 */
	int16_t button_map[KEY_CNT];

	/**
	 * Maps from absolute axis codes to absolute axis
	 * indices, non-present axes map to -1, other
	 * values are in [0, `.nabsolute_axes`[.
	 */
	int16_t absolute_axis_map[ABS_CNT];

	/**
	 * Maps from relative axis codes to absolute axis
	 * indices, non-present axes map to -1, other
	 * values are in [0, `.nrelative_axes`[.
	 */
	int16_t relative_axis_map[REL_CNT];

	/**
	 * Bitmap of supported force feedback effects
	 */
	uint8_t force_feedback_support[(FF_CNT + 7) / 8];
};


/* FOR INTERNAL USE */
void libgamepad_construct_force_feedback_effect__(struct ff_effect *, const struct ff_effect *, double, uint16_t, uint16_t);


/**
 * Get a list of all available physical devices
 * 
 * @param   devicesp   Output parameter for the list of devices
 * @param   ndevicesp  Output parameter for the number of listed devices
 * @return             0 on success, -1 on failure
 * 
 * This function may fail for any reason specified for
 * realloc(3), open(3), fdopendir(3), or readdir(3)
 */
int libgamepad_list_superdevices(char ***, size_t *);

/**
 * Get information about a physical device
 * 
 * @param   devicep  Output parameter for the device information,
 *                   allocated memory shall be deallocated with
 *                   `libgamepad_close_superdevice(devicep)`
 * @param   syspath  The path of the device, in /sys
 * @return           0 on success, -1 on failure
 * 
 * This function may fail for any reason specified for
 * realloc(3), openat(3), fdopendir(3), or readdir(3)
 */
int libgamepad_open_superdevice(struct libgamepad_superdevice *, const char *);

/**
 * Deallocate the contents of a `struct libgamepad_superdevice`
 * 
 * @param  device  The structure whose nested memory allocations
 *                 shall be deallocated, may be `NULL`
 */
void libgamepad_close_superdevice(struct libgamepad_superdevice *);


/**
 * Create a device attachment monitor
 * 
 * The user shall poll the returned file descriptor
 * for read-readiness, and whenever it is ready,
 * call `libgamepad_get_attachment_event`
 * 
 * @param   monitorp  Output parameter for the monitor, shall deallocated with
 *                    `libgamepad_destroy_attachment_monitor` when no longer used
 * @return            A file descriptor on successful completion, -1 on failure
 *
 * This function may fail for any reason specified by
 * malloc(3), udev_new(3), udev_monitor_new_from_netlink(3), or
 * udev_monitor_enable_receiving(3)
 */
int libgamepad_create_attachment_monitor(LIBGAMEPAD_ATTACHMENT_MONITOR **);

/**
 * Deallocate a device attachment monitor
 * 
 * @param  monitor  The monitor to deallocate; the file descriptor returned
 *                  with it will also be closed and become invalid, may be `NULL`
 */
void libgamepad_destroy_attachment_monitor(LIBGAMEPAD_ATTACHMENT_MONITOR *);

/**
 * Get the next device attachment event
 * 
 * @param   monitor   Monitor created with `libgamepad_create_attachment_monitor`
 * @param   syspathp  Pointer to output buffer for the device's path in /sys;
 *                    the buffer may be reallocated by the function
 * @param   sizep     Pointer to the allocation size of `*syspath`; may be
 *                    updated by the function
 * @param   typep     Output parameter for the attachment event type; in the
 *                    event that this value is set to `LIBGAMEPAD_REMOVED`, the
 *                    device is not necessarily on supported by this library
 * @return            1 on success, 0 if the received event was suppressed
 *                    by the library, -1 on failure
 * 
 * This function may fail for any reason specified for
 * realloc(3) or udev_monitor_receive_device(3); notable,
 * this function may set `errno` to `EAGAIN` or `EINTR`
 */
int libgamepad_get_attachment_event(LIBGAMEPAD_ATTACHMENT_MONITOR *, char **, size_t *, enum libgamepad_attachment_event_type *);


/**
 * Open a subdevice
 * 
 * @param   devicep  Output parameter for the device information and handles;
 *                   deallocated with `libgamepad_close_device`
 * @param   dirfd    File descriptor to path that `path` is relative to
 *                   (unless it is an absolute path), or `AT_FDCWD` for the
 *                   current working directory
 * @param   path     The path to the device, if `NULL` or empty, `dirfd`
 *                   will be used as the file descriptor to the device,
 *                   in which case the application must keep it open until
 *                   the device is closed, and then close it manually, and
 *                   `mode` is ignored
 * @param   mode     Mode to open the device in, normally `O_RDONLY`,
 *                   `O_RDONLY|O_NONBLOCK`, `O_RDWR`, or `O_RDWR|O_NONBLOCK`
 * @return           0 on success, -1 on failure
 * 
 * This function may fail for any reason specified for
 * malloc(3), openat(3) or libevdev_new_from_fd(3)
 */
int libgamepad_open_device(struct libgamepad_device *, int, const char *, int);

/**
 * Close a subdevice
 * 
 * @param  device  Device information and handles, may be `NULL`
 */
void libgamepad_close_device(struct libgamepad_device *);

/**
 * Get the next event on a subdevice
 * 
 * NB! events may be queued internally (by libevdev), therefore
 * an application must either call this function in a loop in
 * its own thread, or have the device opened in non-blocking
 * mode and even the poll the device's file descriptor for
 * read-readyness and when it is ready clal this function in
 * a loop until it sets `errno` to `EAGAIN`.
 * 
 * @param   device  Device to read an event from
 * @param   eventp  Output parameter for the event
 * @return          1 if an event was returned,
 *                  0 if no event was returned,
 *                  -1 on failure
 * 
 * This function may fail for any reason specified for
 * libevdev_next_event(3), including:
 * -  EAGAIN  no more data currently available (non-blocking mode)
 * -  EINTR   system call was interrupted, try again
 * -  ENODEV  device has been unplugged or access has been revoked
 */
int libgamepad_next_event(struct libgamepad_device *, struct libgamepad_input_event *);


/**
 * Get the name of a button/key
 * 
 * @param   code  The button/key
 * @return        The button/key's name
 */
inline const char *
libgamepad_get_button_name(uint16_t code)
{
	return libevdev_event_code_get_name(EV_KEY, (unsigned int)code);
}

/**
 * Get the name of an absolute axis
 * 
 * @param   code  The axis
 * @return        The axis' name
 */
inline const char *
libgamepad_get_absolute_axis_name(uint16_t code)
{
	return libevdev_event_code_get_name(EV_ABS, (unsigned int)code);
}

/**
 * Get the name of a relative axis
 * 
 * @param   code  The axis
 * @return        The axis' name
 */
inline const char *
libgamepad_get_relative_axis_name(uint16_t code)
{
	return libevdev_event_code_get_name(EV_REL, (unsigned int)code);
}

/**
 * Get whether a button/key is pressed down or not
 *
 * @param   device  The device to retrieve the information for
 * @param   code    The button/key
 * @return          1 if the button/key is pressed down,
 *                  0 otherwise
 */
inline int
libgamepad_get_button_is_pressed(struct libgamepad_device *device, uint16_t code)
{
	return libevdev_get_event_value(device->dev, EV_KEY, (unsigned int)code);
}

/**
 * Get information about an absolute axis
 *
 * @param   device  The device to retrieve the information for
 * @param   code    The axis
 * @return          Information about the axis
 */
inline const struct input_absinfo * /* `struct input_absinfo` is defined in <linux/input.h> */
libgamepad_get_absolute_axis_info(struct libgamepad_device *device, uint16_t code)
{
	return libevdev_get_abs_info(device->dev, (unsigned int)code);
}


/**
 * Grab a subdevice, if not already grabbed
 *
 * This is supposed to block out clients from
 * retrieving events for the device, but it
 * does not necessarily stop them from reading
 * the device state
 * 
 * @param   device  The device to grab
 * @return          0 on success, -1 on failure
 * 
 * In the event that the device is already grabbed by
 * via another open file descriptor (duplicates share
 * grab), this function will return -1 and set `errno`
 * to `EBUSY`
 */
inline int
libgamepad_grab(struct libgamepad_device *device)
{
	return ioctl(device->fd, EVIOCGRAB, (void *)1);
}

/**
 * Ungrab a subdevice, unless not currently grabbed
 * 
 * @param   device  The device to ungrab
 * @return          0 on success, -1 on failure
 */
inline int
libgamepad_ungrab(struct libgamepad_device *device)
{
	return ioctl(device->fd, EVIOCGRAB, (void *)0);
}


/**
 * Set the clock that event timestamps shall be reported in
 * 
 * @param   device   The device to configure
 * @param   clockid  The clock to use on event timestamps
 * @return           0 on success, -1 on failure
 */
inline int
libgamepad_set_clock(struct libgamepad_device *device, clockid_t clockid)
{
	return ioctl(device->fd, EVIOCSCLOCKID, &clockid);
}


/**
 * Install a force feedback effect that can be played back later
 * 
 * @param   device  The device to configure
 * @param   effect  The effect to install; will be edited, specifically the ID
 *                  will be set (need not be set before calling this function)
 * @return          0 on success, -1 on failure
 */
inline int /* `struct ff_effect` is defined in <linux/input.h> */
libgamepad_install_force_feedback_effect(struct libgamepad_device *device, struct ff_effect *effect)
{
	effect->id = -1;
	return ioctl(device->fd, EVIOCSFF, effect);
}

/**
 * Reconfigure an already installed force feedback effect
 * 
 * @param   device  The device to configure
 * @param   effect  The effect to update, the ID must be set to the ID of a
 *                  previously installed effect
 * @return          0 on success, -1 on failure
 */
inline int
libgamepad_update_force_feedback_effect(struct libgamepad_device *device, struct ff_effect *effect)
{
	return ioctl(device->fd, EVIOCSFF, effect);
}

/**
 * Uninstall an installed force feedback effect
 * 
 * @param   device  The device to configure
 * @param   effect  The effect to remove, the ID must be set to the ID of a
 *                  previously installed effect and will be reset
 * @return          0 on success, -1 on failure
 */
inline int
libgamepad_uninstall_force_feedback_effect(struct libgamepad_device *device, struct ff_effect *effect)
{
	int ret = ioctl(device->fd, EVIOCRMFF, effect);
	effect->id = -1;
	return ret;
}

/**
 * Get the number of force feedback effects that can be played concurrently
 * 
 * @param   device  The device to configure
 * @return          The number of maximum number concurrent effects, -1 on failure
 */
inline int
libgamepad_get_force_feedback_max_concurrency(struct libgamepad_device *device)
{
	int num;
	return ioctl(device->fd, EVIOCGEFFECTS, &num) ? -1 : num;
}

/**
 * Play a force feedback effect
 * 
 * @param   device  The device to play the force feedback effect on
 * @param   effect  The force feedback effect to play, must already be installed
 *                  with `libgamepad_install_force_feedback_effect`
 * @return          0 on success, -1 on failure
 */
inline int
libgamepad_play_force_feedback_effect(struct libgamepad_device *device, const struct ff_effect *effect)
{
	struct input_event message;
	message.type = EV_FF;
	message.code = (uint16_t)effect->id;
	message.value = 1;
	return write(device->fd, &message, sizeof(message)) < 0 ? -1 : 0;
}

/**
 * Stop playing a force feedback effect
 * 
 * @param   device  The device playing the force feedback effect on
 * @param   effect  The force feedback effect to play, must already be installed
 *                  with `libgamepad_install_force_feedback_effect`
 * @return          0 on success, -1 on failure
 */
inline int
libgamepad_stop_force_feedback_effect(struct libgamepad_device *device, const struct ff_effect *effect)
{
	struct input_event message;
	message.type = EV_FF;
	message.code = (uint16_t)effect->id;
	message.value = 0;
	return write(device->fd, &message, sizeof(message)) < 0 ? -1 : 0;
}

/**
 * Check if a force feedback effect or waveform is supported
 *
 * @param   device  The device to check force feedback support on
 * @param   effect  The force feedback effect or waveform
 * @return          1 if the effect/waveform is supported, 0 otherwise
 */
inline int
libgamepad_is_force_feedback_effect_supported(struct libgamepad_device *device, uint16_t effect)
{
	return effect < sizeof(device->force_feedback_support) * 8 &&
	       ((device->force_feedback_support[effect / 8] >> (effect % 8)) & 1);
}

/**
 * Set the force feedback master gain on a device
 * 
 * Requires support for `FF_GAIN` (check with
 * `libgamepad_is_force_feedback_effect_supported`)
 * 
 * @param   device  The device to configure
 * @param   gain    The master gain, shall be a value in [0, 0xFFFF]
 * @return          0 on success, -1 on failure
 */
inline int
libgamepad_set_force_feedback_master_gain(struct libgamepad_device *device, uint16_t gain)
{
	struct input_event message;
	message.type = EV_FF;
	message.code = FF_GAIN;
	message.value = (int16_t)gain;
	return write(device->fd, &message, sizeof(message)) < 0 ? -1 : 0;
}

/**
 * Set the autocenter force feedback on a device
 * 
 * Requires support for `FF_AUTOCENTER` (check with
 * `libgamepad_is_force_feedback_effect_supported`)
 * 
 * @param   device      The device to configure
 * @param   autocenter  Autocenter strength, shall be a value in [0, 0xFFFF], select 0 to
 *                      disable (you can also use `libgamepad_disable_force_feedback_autocenter`)
 * @return              0 on success, -1 on failure
 */
inline int
libgamepad_set_force_feedback_autocenter(struct libgamepad_device *device, uint16_t autocenter)
{
	struct input_event message;
	message.type = EV_FF;
	message.code = FF_AUTOCENTER;
	message.value = (int16_t)autocenter;
	return write(device->fd, &message, sizeof(message)) < 0 ? -1 : 0;
}

/**
 * Disable the autocenter force feedback on a device
 * 
 * Requires support for `FF_AUTOCENTER` (check with
 * `libgamepad_is_force_feedback_effect_supported`)
 * 
 * @param   device  device to configure
 * @return          0 on success, -1 on failure
 */
inline int
libgamepad_disable_force_feedback_autocenter(struct libgamepad_device *device)
{
	struct input_event message;
	message.type = EV_FF;
	message.code = FF_AUTOCENTER;
	message.value = 0;
	return write(device->fd, &message, sizeof(message)) < 0 ? -1 : 0;
}

/**
 * Construct a rumble force-feedback effect
 * 
 * Requires support for `FF_RUMBLE` (check with
 * `libgamepad_is_force_feedback_effect_supported`)
 * 
 * This function will set the following values to
 * zero if `from` is `NULL`, see <linux/input.h>
 * for more details:
 * -  effectp->trigger.button
 * -  effectp->trigger.interval
 * -  effectp->replay.delay
 * 
 * @param  effectp    Output parameter for the effect
 * @param  from       Effect to reconfigure, `NULL` to create a new effect
 * @param  direction  The direction of the force feedback (if directional), where
 *                    values are measure clockwise and both 0 and 1 are upwards
 * @param  length     The number of milliseconds the effect is played
 * @param  effect     Effect specific details:
 *                    - .strong_magnitude  Heavy motor strength, unsigned 16-bit integer
 *                    - .weak_magnitude    Light motor strength, unsigned 16-bit integer
 */
inline void
libgamepad_construct_rumble_force_feedback_effect(struct ff_effect *effectp, const struct ff_effect *from,
                                                  double direction, uint16_t length, const struct ff_rumble_effect *effect)
{
	libgamepad_construct_force_feedback_effect__(effectp, from, direction, length, FF_RUMBLE);
	memcpy(&effectp->u.rumble, effect, sizeof(effectp->u.rumble));
}

/**
 * Construct a constant force-feedback effect
 * 
 * Requires support for `FF_CONSTANT` (check with
 * `libgamepad_is_force_feedback_effect_supported`)
 * 
 * This function will set the following values to
 * zero if `from` is `NULL`, see <linux/input.h>
 * for more details:
 * -  effectp->trigger.button
 * -  effectp->trigger.interval
 * -  effectp->replay.delay
 * 
 * @param  effectp    Output parameter for the effect
 * @param  from       Effect to reconfigure, `NULL` to create a new effect
 * @param  direction  The direction of the force feedback (if directional), where
 *                    values are measure clockwise and both 0 and 1 are upwards
 * @param  length     The number of milliseconds the effect is played
 * @param  effect     Effect specific details:
 *                    - .level                     Strength, signed 16-bit integer
 *                    - .envelope.attack_strength  Strength at beginning, unsigned 16-bit integer
 *                    - .envelope.fade_strength    Strength at end, unsigned 16-bit integer
 *                    - .envelope.attack_length    The number of milliseconds the strength shall
 *                                                 transition from `.envelope.attack_strength`
 *                                                 to `.level`, unsigned 16-bit integer
 *                    - .envelope.fade_length      The number of milliseconds the strength shall
 *                                                 transition to `.envelope.fade_strength`
 *                                                 from `.level`, unsigned 16-bit integer
 */
inline void
libgamepad_construct_constant_force_feedback_effect(struct ff_effect *effectp, const struct ff_effect *from,
                                                    double direction, uint16_t length, const struct ff_constant_effect *effect)
{
	libgamepad_construct_force_feedback_effect__(effectp, from, direction, length, FF_CONSTANT);
	memcpy(&effectp->u.constant, effect, sizeof(effectp->u.constant));
}

/**
 * Construct a ramp force-feedback effect
 * 
 * Requires support for `FF_RAMP` (check with
 * `libgamepad_is_force_feedback_effect_supported`)
 * 
 * This function will set the following values to
 * zero if `from` is `NULL`, see <linux/input.h>
 * for more details:
 * -  effectp->trigger.button
 * -  effectp->trigger.interval
 * -  effectp->replay.delay
 * 
 * @param  effectp    Output parameter for the effect
 * @param  from       Effect to reconfigure, `NULL` to create a new effect
 * @param  direction  The direction of the force feedback (if directional), where
 *                    values are measure clockwise and both 0 and 1 are upwards
 * @param  length     The number of milliseconds the effect is played
 * @param  effect     Effect specific details:
 *                    - .start_level               Strength at beginning, signed 16-bit integer
 *                    - .end_level                 Strength at end, signed 16-bit integer
 *                    - .envelope.attack_strength  Strength at beginning, unsigned 16-bit integer
 *                    - .envelope.fade_strength    Strength at end, unsigned 16-bit integer
 *                    - .envelope.attack_length    The number of milliseconds the strength shall
 *                                                 transition from `.envelope.attack_strength`,
 *                                                 unsigned 16-bit integer
 *                    - .envelope.fade_length      The number of milliseconds the strength shall
 *                                                 transition to `.envelope.fade_strength`,
 *                                                 unsigned 16-bit integer
 */
inline void
libgamepad_construct_ramp_force_feedback_effect(struct ff_effect *effectp, const struct ff_effect *from,
                                                double direction, uint16_t length, const struct ff_ramp_effect *effect)
{
	libgamepad_construct_force_feedback_effect__(effectp, from, direction, length, FF_RUMBLE);
	memcpy(&effectp->u.ramp, effect, sizeof(effectp->u.ramp));
}

/**
 * Construct a periodic force-feedback effect
 * 
 * Requires support for `FF_PERIODIC` and the selected waveform
 * (check with `libgamepad_is_force_feedback_effect_supported`)
 * 
 * This function will set the following values to
 * zero if `from` is `NULL`, see <linux/input.h>
 * for more details:
 * -  effectp->trigger.button
 * -  effectp->trigger.interval
 * -  effectp->replay.delay
 * 
 * @param  effectp    Output parameter for the effect
 * @param  from       Effect to reconfigure, `NULL` to create a new effect
 * @param  direction  The direction of the force feedback (if directional), where
 *                    values are measure clockwise and both 0 and 1 are upwards
 * @param  length     The number of milliseconds the effect is played
 * @param  effect     Effect specific details:
 *                    - .waveform                  `FF_SQUARE`, `FF_TRIANGLE`, `FF_SINE`, `FF_SAW_UP`,
 *                                                 `FF_SAW_DOWN`, or `FF_CUSTOM`
 *                    - .period                    The period of the wave, in milliseconds (unsigned 16-bit integer)
 *                    - .magnitude                 The peak value, signed 16-bit integer
 *                    - .offset                    The rough mean value, signed 16-bit integer
 *                    - .phase                     Horiztonal wave-shift, in milliseconds (unsigned 16-bit integer)
 *                    - .envelope.attack_strength  Strength at beginning, unsigned 16-bit integer
 *                    - .envelope.fade_strength    Strength at end, unsigned 16-bit integer
 *                    - .envelope.attack_length    The number of milliseconds the strength shall
 *                                                 transition from `.envelope.attack_strength`,
 *                                                 unsigned 16-bit integer
 *                    - .envelope.fade_length      The number of milliseconds the strength shall
 *                                                 transition to `.envelope.fade_strength`,
 *                                                 unsigned 16-bit integer
 *                    - .custom_len                Set to zero unless you are using (`FF_CUSTOM`)
 *                    - .custom_data               Set to `NULL` unless you are using (`FF_CUSTOM`)
 */
inline void
libgamepad_construct_periodic_force_feedback_effect(struct ff_effect *effectp, const struct ff_effect *from,
                                                   double direction, uint16_t length, const struct ff_periodic_effect *effect)
{
	libgamepad_construct_force_feedback_effect__(effectp, from, direction, length, FF_PERIODIC);
	memcpy(&effectp->u.periodic, effect, sizeof(effectp->u.periodic));
}

/**
 * Construct a spring force-feedback effect
 * 
 * Requires support for `FF_SPRING` (check with
 * `libgamepad_is_force_feedback_effect_supported`)
 * 
 * This function will set the following values to
 * zero if `from` is `NULL`, see <linux/input.h>
 * for more details:
 * -  effectp->trigger.button
 * -  effectp->trigger.interval
 * -  effectp->replay.delay
 * 
 * @param  effectp    Output parameter for the effect
 * @param  from       Effect to reconfigure, `NULL` to create a new effect
 * @param  direction  The direction of the force feedback (if directional), where
 *                    values are measure clockwise and both 0 and 1 are upwards
 * @param  length     The number of milliseconds the effect is played
 * @param  effect     Effect specific details (one of each axis):
 *                    - .right_saturation  Maximum level at end of axis, unsigned 16-bit integer
 *                    - .left_saturation   Maximum level at beginning of axis, unsigned 16-bit integer
 *                    - .right_coeff       Growth coefficient after the dead zone, signed 16-bit integer
 *                    - .left_coeff        Growth coefficient before the dead zone, signed 16-bit integer
 *                    - .deadband          Size of the dead zone
 *                    - .center            The position of the center of the dead zone
 */
inline void
libgamepad_construct_spring_force_feedback_effect(struct ff_effect *effectp, const struct ff_effect *from,
                                                  double direction, uint16_t length, const struct ff_condition_effect effect[2])
{
	libgamepad_construct_force_feedback_effect__(effectp, from, direction, length, FF_SPRING);
	memcpy(effectp->u.condition, effect, sizeof(effectp->u.condition));
}

/**
 * Construct a friction force-feedback effect
 * 
 * Requires support for `FF_FRICTION` (check with
 * `libgamepad_is_force_feedback_effect_supported`)
 * 
 * This function will set the following values to
 * zero if `from` is `NULL`, see <linux/input.h>
 * for more details:
 * -  effectp->trigger.button
 * -  effectp->trigger.interval
 * -  effectp->replay.delay
 * 
 * @param  effectp    Output parameter for the effect
 * @param  from       Effect to reconfigure, `NULL` to create a new effect
 * @param  direction  The direction of the force feedback (if directional), where
 *                    values are measure clockwise and both 0 and 1 are upwards
 * @param  length     The number of milliseconds the effect is played
 * @param  effect     Effect specific details (one of each axis):
 *                    - .right_saturation  Maximum level at end of axis, unsigned 16-bit integer
 *                    - .left_saturation   Maximum level at beginning of axis, unsigned 16-bit integer
 *                    - .right_coeff       Growth coefficient after the dead zone, signed 16-bit integer
 *                    - .left_coeff        Growth coefficient before the dead zone, signed 16-bit integer
 *                    - .deadband          Size of the dead zone
 *                    - .center            The position of the center of the dead zone
 */
inline void
libgamepad_construct_friction_force_feedback_effect(struct ff_effect *effectp, const struct ff_effect *from,
                                                    double direction, uint16_t length, const struct ff_condition_effect effect[2])
{
	libgamepad_construct_force_feedback_effect__(effectp, from, direction, length, FF_FRICTION);
	memcpy(effectp->u.condition, effect, sizeof(effectp->u.condition));
}

/**
 * Construct a damper force-feedback effect
 * 
 * Requires support for `FF_DAMPER` (check with
 * `libgamepad_is_force_feedback_effect_supported`)
 * 
 * This function will set the following values to
 * zero if `from` is `NULL`, see <linux/input.h>
 * for more details:
 * -  effectp->trigger.button
 * -  effectp->trigger.interval
 * -  effectp->replay.delay
 * 
 * @param  effectp    Output parameter for the effect
 * @param  from       Effect to reconfigure, `NULL` to create a new effect
 * @param  direction  The direction of the force feedback (if directional), where
 *                    values are measure clockwise and both 0 and 1 are upwards
 * @param  length     The number of milliseconds the effect is played
 * @param  effect     Effect specific details (one of each axis):
 *                    - .right_saturation  Maximum level at end of axis, unsigned 16-bit integer
 *                    - .left_saturation   Maximum level at beginning of axis, unsigned 16-bit integer
 *                    - .right_coeff       Growth coefficient after the dead zone, signed 16-bit integer
 *                    - .left_coeff        Growth coefficient before the dead zone, signed 16-bit integer
 *                    - .deadband          Size of the dead zone
 *                    - .center            The position of the center of the dead zone
 */
inline void
libgamepad_construct_damper_force_feedback_effect(struct ff_effect *effectp, const struct ff_effect *from,
                                                  double direction, uint16_t length, const struct ff_condition_effect effect[2])
{
	libgamepad_construct_force_feedback_effect__(effectp, from, direction, length, FF_DAMPER);
	memcpy(effectp->u.condition, effect, sizeof(effectp->u.condition));
}

/**
 * Construct a inertia force-feedback effect
 * 
 * Requires support for `FF_INERTIA` (check with
 * `libgamepad_is_force_feedback_effect_supported`)
 * 
 * This function will set the following values to
 * zero if `from` is `NULL`, see <linux/input.h>
 * for more details:
 * -  effectp->trigger.button
 * -  effectp->trigger.interval
 * -  effectp->replay.delay
 * 
 * @param  effectp    Output parameter for the effect
 * @param  from       Effect to reconfigure, `NULL` to create a new effect
 * @param  direction  The direction of the force feedback (if directional), where
 *                    values are measure clockwise and both 0 and 1 are upwards
 * @param  length     The number of milliseconds the effect is played
 * @param  effect     Effect specific details (one of each axis):
 *                    - .right_saturation  Maximum level at end of axis, unsigned 16-bit integer
 *                    - .left_saturation   Maximum level at beginning of axis, unsigned 16-bit integer
 *                    - .right_coeff       Growth coefficient after the dead zone, signed 16-bit integer
 *                    - .left_coeff        Growth coefficient before the dead zone, signed 16-bit integer
 *                    - .deadband          Size of the dead zone
 *                    - .center            The position of the center of the dead zone
 */
inline void
libgamepad_construct_inertia_force_feedback_effect(struct ff_effect *effectp, const struct ff_effect *from,
                                                   double direction, uint16_t length, const struct ff_condition_effect effect[2])
{
	libgamepad_construct_force_feedback_effect__(effectp, from, direction, length, FF_INERTIA);
	memcpy(effectp->u.condition, effect, sizeof(effectp->u.condition));
}


#endif