uhid-example.c
/*
* UHID Example
*
* Copyright (c) 2012-2013 David Herrmann <dh.herrmann@gmail.com>
*
* The code may be used by anyone for any purpose,
* and can serve as a starting point for developing
* applications using uhid.
*/
/*
* UHID Example
* This example emulates a basic 3 buttons mouse with wheel over UHID. Run this
* program as root and then use the following keys to control the mouse:
* q: Quit the application
* 1: Toggle left button (down, up, ...)
* 2: Toggle right button
* 3: Toggle middle button
* a: Move mouse left
* d: Move mouse right
* w: Move mouse up
* s: Move mouse down
* r: Move wheel up
* f: Move wheel down
*
* Additionally to 3 button mouse, 3 keyboard LEDs are also supported (LED_NUML,
* LED_CAPSL and LED_SCROLLL). The device doesn't generate any related keyboard
* events, though. You need to manually write the EV_LED/LED_XY/1 activation
* input event to the evdev device to see it being sent to this device.
*
* If uhid is not available as /dev/uhid, then you can pass a different path as
* first argument.
* If <linux/uhid.h> is not installed in /usr, then compile this with:
* gcc -o ./uhid_test -Wall -I./include ./samples/uhid/uhid-example.c
* And ignore the warning about kernel headers. However, it is recommended to
* use the installed uhid.h if available.
*/
#include <errno.h>
#include <fcntl.h>
#include <poll.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <termios.h>
#include <unistd.h>
#include <linux/uhid.h>
/*
* HID Report Desciptor
* We emulate a basic 3 button mouse with wheel and 3 keyboard LEDs. This is
* the report-descriptor as the kernel will parse it:
*
* INPUT(1)[INPUT]
* Field(0)
* Physical(GenericDesktop.Pointer)
* Application(GenericDesktop.Mouse)
* Usage(3)
* Button.0001
* Button.0002
* Button.0003
* Logical Minimum(0)
* Logical Maximum(1)
* Report Size(1)
* Report Count(3)
* Report Offset(0)
* Flags( Variable Absolute )
* Field(1)
* Physical(GenericDesktop.Pointer)
* Application(GenericDesktop.Mouse)
* Usage(3)
* GenericDesktop.X
* GenericDesktop.Y
* GenericDesktop.Wheel
* Logical Minimum(-128)
* Logical Maximum(127)
* Report Size(8)
* Report Count(3)
* Report Offset(8)
* Flags( Variable Relative )
* OUTPUT(2)[OUTPUT]
* Field(0)
* Application(GenericDesktop.Keyboard)
* Usage(3)
* LED.NumLock
* LED.CapsLock
* LED.ScrollLock
* Logical Minimum(0)
* Logical Maximum(1)
* Report Size(1)
* Report Count(3)
* Report Offset(0)
* Flags( Variable Absolute )
*
* This is the mapping that we expect:
* Button.0001 ---> Key.LeftBtn
* Button.0002 ---> Key.RightBtn
* Button.0003 ---> Key.MiddleBtn
* GenericDesktop.X ---> Relative.X
* GenericDesktop.Y ---> Relative.Y
* GenericDesktop.Wheel ---> Relative.Wheel
* LED.NumLock ---> LED.NumLock
* LED.CapsLock ---> LED.CapsLock
* LED.ScrollLock ---> LED.ScrollLock
*
* This information can be verified by reading /sys/kernel/debug/hid/<dev>/rdesc
* This file should print the same information as showed above.
*/
static unsigned char rdesc[] = {
0x05, 0x01, /* USAGE_PAGE (Generic Desktop) */
0x09, 0x02, /* USAGE (Mouse) */
0xa1, 0x01, /* COLLECTION (Application) */
0x09, 0x01, /* USAGE (Pointer) */
0xa1, 0x00, /* COLLECTION (Physical) */
0x85, 0x01, /* REPORT_ID (1) */
0x05, 0x09, /* USAGE_PAGE (Button) */
0x19, 0x01, /* USAGE_MINIMUM (Button 1) */
0x29, 0x03, /* USAGE_MAXIMUM (Button 3) */
0x15, 0x00, /* LOGICAL_MINIMUM (0) */
0x25, 0x01, /* LOGICAL_MAXIMUM (1) */
0x95, 0x03, /* REPORT_COUNT (3) */
0x75, 0x01, /* REPORT_SIZE (1) */
0x81, 0x02, /* INPUT (Data,Var,Abs) */
0x95, 0x01, /* REPORT_COUNT (1) */
0x75, 0x05, /* REPORT_SIZE (5) */
0x81, 0x01, /* INPUT (Cnst,Var,Abs) */
0x05, 0x01, /* USAGE_PAGE (Generic Desktop) */
0x09, 0x30, /* USAGE (X) */
0x09, 0x31, /* USAGE (Y) */
0x09, 0x38, /* USAGE (WHEEL) */
0x15, 0x81, /* LOGICAL_MINIMUM (-127) */
0x25, 0x7f, /* LOGICAL_MAXIMUM (127) */
0x75, 0x08, /* REPORT_SIZE (8) */
0x95, 0x03, /* REPORT_COUNT (3) */
0x81, 0x06, /* INPUT (Data,Var,Rel) */
0xc0, /* END_COLLECTION */
0xc0, /* END_COLLECTION */
0x05, 0x01, /* USAGE_PAGE (Generic Desktop) */
0x09, 0x06, /* USAGE (Keyboard) */
0xa1, 0x01, /* COLLECTION (Application) */
0x85, 0x02, /* REPORT_ID (2) */
0x05, 0x08, /* USAGE_PAGE (Led) */
0x19, 0x01, /* USAGE_MINIMUM (1) */
0x29, 0x03, /* USAGE_MAXIMUM (3) */
0x15, 0x00, /* LOGICAL_MINIMUM (0) */
0x25, 0x01, /* LOGICAL_MAXIMUM (1) */
0x95, 0x03, /* REPORT_COUNT (3) */
0x75, 0x01, /* REPORT_SIZE (1) */
0x91, 0x02, /* Output (Data,Var,Abs) */
0x95, 0x01, /* REPORT_COUNT (1) */
0x75, 0x05, /* REPORT_SIZE (5) */
0x91, 0x01, /* Output (Cnst,Var,Abs) */
0xc0, /* END_COLLECTION */
};
static int uhid_write(int fd, const struct uhid_event *ev)
{
ssize_t ret;
ret = write(fd, ev, sizeof(*ev));
if (ret < 0) {
fprintf(stderr, "Cannot write to uhid: %m\n");
return -errno;
} else if (ret != sizeof(*ev)) {
fprintf(stderr, "Wrong size written to uhid: %ld != %lu\n",
ret, sizeof(ev));
return -EFAULT;
} else {
return 0;
}
}
static int create(int fd)
{
struct uhid_event ev;
memset(&ev, 0, sizeof(ev));
ev.type = UHID_CREATE;
strcpy((char*)ev.u.create.name, "test-uhid-device");
ev.u.create.rd_data = rdesc;
ev.u.create.rd_size = sizeof(rdesc);
ev.u.create.bus = BUS_USB;
ev.u.create.vendor = 0x15d9;
ev.u.create.product = 0x0a37;
ev.u.create.version = 0;
ev.u.create.country = 0;
return uhid_write(fd, &ev);
}
static void destroy(int fd)
{
struct uhid_event ev;
memset(&ev, 0, sizeof(ev));
ev.type = UHID_DESTROY;
uhid_write(fd, &ev);
}
/* This parses raw output reports sent by the kernel to the device. A normal
* uhid program shouldn't do this but instead just forward the raw report.
* However, for ducomentational purposes, we try to detect LED events here and
* print debug messages for it. */
static void handle_output(struct uhid_event *ev)
{
/* LED messages are adverised via OUTPUT reports; ignore the rest */
if (ev->u.output.rtype != UHID_OUTPUT_REPORT)
return;
/* LED reports have length 2 bytes */
if (ev->u.output.size != 2)
return;
/* first byte is report-id which is 0x02 for LEDs in our rdesc */
if (ev->u.output.data[0] != 0x2)
return;
/* print flags payload */
fprintf(stderr, "LED output report received with flags %x\n",
ev->u.output.data[1]);
}
static int event(int fd)
{
struct uhid_event ev;
ssize_t ret;
memset(&ev, 0, sizeof(ev));
ret = read(fd, &ev, sizeof(ev));
if (ret == 0) {
fprintf(stderr, "Read HUP on uhid-cdev\n");
return -EFAULT;
} else if (ret < 0) {
fprintf(stderr, "Cannot read uhid-cdev: %m\n");
return -errno;
} else if (ret != sizeof(ev)) {
fprintf(stderr, "Invalid size read from uhid-dev: %ld != %lu\n",
ret, sizeof(ev));
return -EFAULT;
}
switch (ev.type) {
case UHID_START:
fprintf(stderr, "UHID_START from uhid-dev\n");
break;
case UHID_STOP:
fprintf(stderr, "UHID_STOP from uhid-dev\n");
break;
case UHID_OPEN:
fprintf(stderr, "UHID_OPEN from uhid-dev\n");
break;
case UHID_CLOSE:
fprintf(stderr, "UHID_CLOSE from uhid-dev\n");
break;
case UHID_OUTPUT:
fprintf(stderr, "UHID_OUTPUT from uhid-dev\n");
handle_output(&ev);
break;
case UHID_OUTPUT_EV:
fprintf(stderr, "UHID_OUTPUT_EV from uhid-dev\n");
break;
default:
fprintf(stderr, "Invalid event from uhid-dev: %u\n", ev.type);
}
return 0;
}
static bool btn1_down;
static bool btn2_down;
static bool btn3_down;
static signed char abs_hor;
static signed char abs_ver;
static signed char wheel;
static int send_event(int fd)
{
struct uhid_event ev;
memset(&ev, 0, sizeof(ev));
ev.type = UHID_INPUT;
ev.u.input.size = 5;
ev.u.input.data[0] = 0x1;
if (btn1_down)
ev.u.input.data[1] |= 0x1;
if (btn2_down)
ev.u.input.data[1] |= 0x2;
if (btn3_down)
ev.u.input.data[1] |= 0x4;
ev.u.input.data[2] = abs_hor;
ev.u.input.data[3] = abs_ver;
ev.u.input.data[4] = wheel;
return uhid_write(fd, &ev);
}
static int keyboard(int fd)
{
char buf[128];
ssize_t ret, i;
ret = read(STDIN_FILENO, buf, sizeof(buf));
if (ret == 0) {
fprintf(stderr, "Read HUP on stdin\n");
return -EFAULT;
} else if (ret < 0) {
fprintf(stderr, "Cannot read stdin: %m\n");
return -errno;
}
for (i = 0; i < ret; ++i) {
switch (buf[i]) {
case '1':
btn1_down = !btn1_down;
ret = send_event(fd);
if (ret)
return ret;
break;
case '2':
btn2_down = !btn2_down;
ret = send_event(fd);
if (ret)
return ret;
break;
case '3':
btn3_down = !btn3_down;
ret = send_event(fd);
if (ret)
return ret;
break;
case 'a':
abs_hor = -20;
ret = send_event(fd);
abs_hor = 0;
if (ret)
return ret;
break;
case 'd':
abs_hor = 20;
ret = send_event(fd);
abs_hor = 0;
if (ret)
return ret;
break;
case 'w':
abs_ver = -20;
ret = send_event(fd);
abs_ver = 0;
if (ret)
return ret;
break;
case 's':
abs_ver = 20;
ret = send_event(fd);
abs_ver = 0;
if (ret)
return ret;
break;
case 'r':
wheel = 1;
ret = send_event(fd);
wheel = 0;
if (ret)
return ret;
break;
case 'f':
wheel = -1;
ret = send_event(fd);
wheel = 0;
if (ret)
return ret;
break;
case 'q':
return -ECANCELED;
default:
fprintf(stderr, "Invalid input: %c\n", buf[i]);
}
}
return 0;
}
int main(int argc, char **argv)
{
int fd;
const char *path = "/dev/uhid";
struct pollfd pfds[2];
int ret;
struct termios state;
ret = tcgetattr(STDIN_FILENO, &state);
if (ret) {
fprintf(stderr, "Cannot get tty state\n");
} else {
state.c_lflag &= ~ICANON;
state.c_cc[VMIN] = 1;
ret = tcsetattr(STDIN_FILENO, TCSANOW, &state);
if (ret)
fprintf(stderr, "Cannot set tty state\n");
}
if (argc >= 2) {
if (!strcmp(argv[1], "-h") || !strcmp(argv[1], "--help")) {
fprintf(stderr, "Usage: %s [%s]\n", argv[0], path);
return EXIT_SUCCESS;
} else {
path = argv[1];
}
}
fprintf(stderr, "Open uhid-cdev %s\n", path);
fd = open(path, O_RDWR | O_CLOEXEC);
if (fd < 0) {
fprintf(stderr, "Cannot open uhid-cdev %s: %m\n", path);
return EXIT_FAILURE;
}
fprintf(stderr, "Create uhid device\n");
ret = create(fd);
if (ret) {
close(fd);
return EXIT_FAILURE;
}
pfds[0].fd = STDIN_FILENO;
pfds[0].events = POLLIN;
pfds[1].fd = fd;
pfds[1].events = POLLIN;
fprintf(stderr, "Press 'q' to quit...\n");
while (1) {
ret = poll(pfds, 2, -1);
if (ret < 0) {
fprintf(stderr, "Cannot poll for fds: %m\n");
break;
}
if (pfds[0].revents & POLLHUP) {
fprintf(stderr, "Received HUP on stdin\n");
break;
}
if (pfds[1].revents & POLLHUP) {
fprintf(stderr, "Received HUP on uhid-cdev\n");
break;
}
if (pfds[0].revents & POLLIN) {
ret = keyboard(fd);
if (ret)
break;
}
if (pfds[1].revents & POLLIN) {
ret = event(fd);
if (ret)
break;
}
}
fprintf(stderr, "Destroy uhid device\n");
destroy(fd);
return EXIT_SUCCESS;
}
