Nunchuk-Mouse - Experimenting with Raspberry Pi - page 56

An example populating these structures is provided next. If you plan to inject
EV_ABS events, you must also populate the abs members, mentioned in the “Configure
EV_ABS ” section.

struct uinput_user_dev uinp;
int rc;

memset(&uinp,0,sizeof uinp);

strncpy(uinp.name,"nunchuk",UINPUT_MAX_NAME_SIZE);

uinp.id.bustype = BUS_USB;
uinp.id.vendor = 0x1;
uinp.id.product = 0x1;
uinp.id.version = 1;

// uinp.absmax[ABS_X] = 1023; / EV_ABS only /

∗ ∗

// ...

rc = write(fd,&uinp,sizeof(uinp));
assert(rc == sizeof(uinp));

The call to write(2) passes all of this important information to the uinput driver.
Now all that remains is to request a device node to be created for application use:

int rc;

rc = ioctl(fd,UI_DEV_CREATE);
assert(!rc);

This step causes the uinput driver to make a device node appear in the pseudo
directory /dev/input . An example is shown here:

$ ls -l /dev/input
total 0
drwxr−xr−x 2 root root 120 Dec 31 1969 by−id
drwxr−xr−x 2 root root 120 Dec 31 1969 by−path
crw−rw−−−T 1 root input 13, 64 Dec 31 1969 event0
crw−rw−−−T 1 root input 13, 65 Dec 31 1969 event1
crw−rw−−−T 1 root input 13, 66 Dec 31 1969 event2
crw−rw−−−T 1 root input 13, 67 Feb 23 13:40 event3
crw−rw−−−T 1 root input 13, 63 Dec 31 1969 mice
crw−rw−−−T 1 root input 13, 32 Dec 31 1969 mouse0
crw−rw−−−T 1 root input 13, 33 Feb 23 13:40 mouse1

The device /dev/input/event3 was the Nunchuck's created uinput node, when the
program was run.