Signed-off-by: Marcos Paulo de Souza <marcos.souza....@gmail.com> --- Documentation/input/uinput.rst | 196 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 196 insertions(+) create mode 100644 Documentation/input/uinput.rst
diff --git a/Documentation/input/uinput.rst b/Documentation/input/uinput.rst new file mode 100644 index 0000000..eb79b77 --- /dev/null +++ b/Documentation/input/uinput.rst @@ -0,0 +1,196 @@ +============= +uinput module +============= + +Introduction +============ + +uinput is a kernel module that makes possible to create and handle input devices +from userspace. By writing to the module's /dev/uinput (or /dev/input/uinput), a +process can create a virtual device with specific capabilities. +Once created, the process can send events through that virtual device. + +Interface +========= + +:: + + linux/uinput.h + +The uinput header defines ioctls to create, setup and destroy virtual devices. + +libevdev +======== + +libevdev is a wrapper library for evdev devices, making uinput setup easier +by skipping a lot of ioctl calls. When dealing with uinput, libevdev is the best +alternative over accessing uinput directly, and it is less error prone. + +For examples and more information about libevdev: +https://cgit.freedesktop.org/libevdev + +Examples +======== + +1.0 Keyboard events +------------------- + +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. + +.. code-block:: c + + #include <linux/uinput.h> + + int fd; + + void emit(int type, int code, int val) + { + struct input_event ie; + + ie.type = type; + ie.code = code; + ie.value = val; + /* below timestamp values are ignored */ + ie.time.tv_sec = 0; + ie.time.tv_usec = 0; + + write(fd, &ie, sizeof(ie)); + } + + int main() { + struct uinput_setup usetup; + + fd = open("/dev/uinput", O_WRONLY | O_NONBLOCK); + + /* the ioctls below enables the to be created device to 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 */ + strcpy(usetup.name, "Example device"); + + ioctl(fd, UI_DEV_SETUP, &usetup); + ioctl(fd, UI_DEV_CREATE); + + /* UI_DEV_CREATE causes the kernel to create the device nodes for this + * device. Insert a pause so that userspace has time to detect, + * initialize the new device, and can start to listen to events from + * this device + **/ + + /* key press, report the event, send key release, and report again */ + emit(EV_KEY, KEY_SPACE, 1); + emit(EV_SYN, SYN_REPORT, 0); + emit(EV_KEY, KEY_SPACE, 0); + emit(EV_SYN, SYN_REPORT, 0); + + ioctl(fd, UI_DEV_DESTROY); + close(fd); + + return 0; + } + +2.0 Mouse movements +------------------- + +This example shows how to create a virtual device that behaves like a physical +mouse. + +.. code-block:: c + + #include <linux/uinput.h> + + /* emit function is identical to of the first example */ + + struct uinput_setup usetup; + int i = 50; + + 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 */ + strcpy(usetup.name, "Example device"); + + ioctl(fd, UI_DEV_SETUP, &usetup); + ioctl(fd, UI_DEV_CREATE); + + /* UI_DEV_CREATE causes the kernel to create the device nodes for this + * device. Insert a pause so that userspace has time to detect, + * initialize the new device, and can start to listen to events from + * this device + **/ + + /* moves the mouse diagonally, 5 units per axis */ + while (i--) { + emit(EV_REL, REL_X, 5); + emit(EV_REL, REL_Y, 5); + emit(EV_SYN, SYN_REPORT, 0); + usleep(15000); + } + + ioctl(fd, UI_DEV_DESTROY); + close(fd); + + return 0; + +3.0 uinput old interface +------------------------ + +Before kernel 4.5, uinput didn't have an ioctl to setup a virtual device. When +running a version prior to 4.5, the user needs to fill a different struct and +call write on the uinput file descriptor. + +.. code-block:: c + + #include <linux/uinput.h> + + /* emit function is identical to of the first example */ + + struct uinput_user_dev uud; + + fd = open("/dev/uinput", O_WRONLY | O_NONBLOCK); + + /* the ioctls below enables the to be created device to 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); + + /* UI_DEV_CREATE causes the kernel to create the device nodes for this + * device. Insert a pause so that userspace has time to detect, + * initialize the new device, and can start to listen to events from + * this device + **/ + + /* key press, report the event, send key release, and report again */ + emit(EV_KEY, KEY_SPACE, 1); + emit(EV_SYN, SYN_REPORT, 0); + emit(EV_KEY, KEY_SPACE, 0); + emit(EV_SYN, SYN_REPORT, 0); + + ioctl(fd, UI_DEV_DESTROY); + close(fd); + + return 0; + -- 2.9.3
