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Add description of uinput module with a few examples. Signed-off-by: Marcos Paulo de Souza <marcos.souza.org@gmail.com> Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
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@@ -18,4 +18,5 @@ Linux Input Subsystem userspace API | |
gamepad | ||
ff | ||
joydev/index | ||
uinput | ||
userio |
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============= | ||
uinput module | ||
============= | ||
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Introduction | ||
============ | ||
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uinput is a kernel module that makes it possible to emulate input devices | ||
from userspace. By writing to /dev/uinput (or /dev/input/uinput) device, a | ||
process can create a virtual input device with specific capabilities. Once | ||
this virtual device is created, the process can send events through it, | ||
that will be delivered to userspace and in-kernel consumers. | ||
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Interface | ||
========= | ||
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:: | ||
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linux/uinput.h | ||
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The uinput header defines ioctls to create, set up, and destroy virtual | ||
devices. | ||
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libevdev | ||
======== | ||
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libevdev is a wrapper library for evdev devices that provides interfaces to | ||
create uinput devices and send events. libevdev is less error-prone than | ||
accessing uinput directly, and should be considered for new software. | ||
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For examples and more information about libevdev: | ||
https://www.freedesktop.org/software/libevdev/doc/latest/ | ||
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Examples | ||
======== | ||
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Keyboard events | ||
--------------- | ||
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This first example shows how to create a new virtual device, and how to | ||
send a key event. All default imports and error handlers were removed for | ||
the sake of simplicity. | ||
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.. code-block:: c | ||
#include <linux/uinput.h> | ||
void emit(int fd, int type, int code, int val) | ||
{ | ||
struct input_event ie; | ||
ie.type = type; | ||
ie.code = code; | ||
ie.value = val; | ||
/* timestamp values below are ignored */ | ||
ie.time.tv_sec = 0; | ||
ie.time.tv_usec = 0; | ||
write(fd, &ie, sizeof(ie)); | ||
} | ||
int main(void) | ||
{ | ||
struct uinput_setup usetup; | ||
int fd = open("/dev/uinput", O_WRONLY | O_NONBLOCK); | ||
/* | ||
* The ioctls below will enable the device that is about to be | ||
* created, to pass key events, in this case the space key. | ||
*/ | ||
ioctl(fd, UI_SET_EVBIT, EV_KEY); | ||
ioctl(fd, UI_SET_KEYBIT, KEY_SPACE); | ||
memset(&usetup, 0, sizeof(usetup)); | ||
usetup.id.bustype = BUS_USB; | ||
usetup.id.vendor = 0x1234; /* sample vendor */ | ||
usetup.id.product = 0x5678; /* sample product */ | ||
strcpy(usetup.name, "Example device"); | ||
ioctl(fd, UI_DEV_SETUP, &usetup); | ||
ioctl(fd, UI_DEV_CREATE); | ||
/* | ||
* On UI_DEV_CREATE the kernel will create the device node for this | ||
* device. We are inserting a pause here so that userspace has time | ||
* to detect, initialize the new device, and can start listening to | ||
* the event, otherwise it will not notice the event we are about | ||
* to send. This pause is only needed in our example code! | ||
*/ | ||
sleep(1); | ||
/* Key press, report the event, send key release, and report again */ | ||
emit(fd, EV_KEY, KEY_SPACE, 1); | ||
emit(fd, EV_SYN, SYN_REPORT, 0); | ||
emit(fd, EV_KEY, KEY_SPACE, 0); | ||
emit(fd, EV_SYN, SYN_REPORT, 0); | ||
/* | ||
* Give userspace some time to read the events before we destroy the | ||
* device with UI_DEV_DESTOY. | ||
*/ | ||
sleep(1); | ||
ioctl(fd, UI_DEV_DESTROY); | ||
close(fd); | ||
return 0; | ||
} | ||
Mouse movements | ||
--------------- | ||
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This example shows how to create a virtual device that behaves like a physical | ||
mouse. | ||
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.. code-block:: c | ||
#include <linux/uinput.h> | ||
/* emit function is identical to of the first example */ | ||
int main(void) | ||
{ | ||
struct uinput_setup usetup; | ||
int i = 50; | ||
int fd = open("/dev/uinput", O_WRONLY | O_NONBLOCK); | ||
/* enable mouse button left and relative events */ | ||
ioctl(fd, UI_SET_EVBIT, EV_KEY); | ||
ioctl(fd, UI_SET_KEYBIT, BTN_LEFT); | ||
ioctl(fd, UI_SET_EVBIT, EV_REL); | ||
ioctl(fd, UI_SET_RELBIT, REL_X); | ||
ioctl(fd, UI_SET_RELBIT, REL_Y); | ||
memset(&usetup, 0, sizeof(usetup)); | ||
usetup.id.bustype = BUS_USB; | ||
usetup.id.vendor = 0x1234; /* sample vendor */ | ||
usetup.id.product = 0x5678; /* sample product */ | ||
strcpy(usetup.name, "Example device"); | ||
ioctl(fd, UI_DEV_SETUP, &usetup); | ||
ioctl(fd, UI_DEV_CREATE); | ||
/* | ||
* On UI_DEV_CREATE the kernel will create the device node for this | ||
* device. We are inserting a pause here so that userspace has time | ||
* to detect, initialize the new device, and can start listening to | ||
* the event, otherwise it will not notice the event we are about | ||
* to send. This pause is only needed in our example code! | ||
*/ | ||
sleep(1); | ||
/* Move the mouse diagonally, 5 units per axis */ | ||
while (i--) { | ||
emit(fd, EV_REL, REL_X, 5); | ||
emit(fd, EV_REL, REL_Y, 5); | ||
emit(fd, EV_SYN, SYN_REPORT, 0); | ||
usleep(15000); | ||
} | ||
/* | ||
* Give userspace some time to read the events before we destroy the | ||
* device with UI_DEV_DESTOY. | ||
*/ | ||
sleep(1); | ||
ioctl(fd, UI_DEV_DESTROY); | ||
close(fd); | ||
return 0; | ||
} | ||
uinput old interface | ||
-------------------- | ||
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Before uinput version 5, there wasn't a dedicated ioctl to set up a virtual | ||
device. Programs supportinf older versions of uinput interface need to fill | ||
a uinput_user_dev structure and write it to the uinput file descriptor to | ||
configure the new uinput device. New code should not use the old interface | ||
but interact with uinput via ioctl calls, or use libevdev. | ||
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.. code-block:: c | ||
#include <linux/uinput.h> | ||
/* emit function is identical to of the first example */ | ||
int main(void) | ||
{ | ||
struct uinput_user_dev uud; | ||
int version, rc, fd; | ||
fd = open("/dev/uinput", O_WRONLY | O_NONBLOCK); | ||
rc = ioctl(fd, UI_GET_VERSION, &version); | ||
if (rc == 0 && version >= 5) { | ||
/* use UI_DEV_SETUP */ | ||
return 0; | ||
} | ||
/* | ||
* The ioctls below will enable the device that is about to be | ||
* created, to pass key events, in this case the space key. | ||
*/ | ||
ioctl(fd, UI_SET_EVBIT, EV_KEY); | ||
ioctl(fd, UI_SET_KEYBIT, KEY_SPACE); | ||
memset(&uud, 0, sizeof(uud)); | ||
snprintf(uud.name, UINPUT_MAX_NAME_SIZE, "uinput old interface"); | ||
write(fd, &uud, sizeof(uud)); | ||
ioctl(fd, UI_DEV_CREATE); | ||
/* | ||
* On UI_DEV_CREATE the kernel will create the device node for this | ||
* device. We are inserting a pause here so that userspace has time | ||
* to detect, initialize the new device, and can start listening to | ||
* the event, otherwise it will not notice the event we are about | ||
* to send. This pause is only needed in our example code! | ||
*/ | ||
sleep(1); | ||
/* Key press, report the event, send key release, and report again */ | ||
emit(fd, EV_KEY, KEY_SPACE, 1); | ||
emit(fd, EV_SYN, SYN_REPORT, 0); | ||
emit(fd, EV_KEY, KEY_SPACE, 0); | ||
emit(fd, EV_SYN, SYN_REPORT, 0); | ||
/* | ||
* Give userspace some time to read the events before we destroy the | ||
* device with UI_DEV_DESTOY. | ||
*/ | ||
sleep(1); | ||
ioctl(fd, UI_DEV_DESTROY); | ||
close(fd); | ||
return 0; | ||
} | ||