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mayunteng_1 f3dba6f46f readme

Signed-off-by: mayunteng_1 <mayunteng@huawei.com>
Change-Id: I413a442a67001ad8811ea467ff8df71908c61554

2022-10-09 16:49:44 +08:00

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libevdev - wrapper library for evdev input devices

libevdev is a wrapper library for evdev devices. it moves the common tasks when dealing with evdev devices into a library and provides a library interface to the callers, thus avoiding erroneous ioctls, etc.

The eventual goal is that libevdev wraps all ioctls available to evdev devices, thus making direct access unnecessary.

Directory structure

README.md                   English description
README_zh.md                Chinese description
export_include/libevdev/    API Definition
include/                    Reference header file
libevdev/                   Encapsulation layer implementation
README.OpenSource           Open Source Description

How OpenHarmony integrates libevdev

1.Header file import

#define EVDEV_H
#include <libevdev/libevdev.h>

2.BUILD.gn add Reference

public_deps += ["//third_party/libevdev:libevdev"]

3.Example of calling libevdev function

// Below is a simple example that shows how libevdev could be used. This example opens a device, checks for relative axes and a left mouse button and if it finds them monitors the device to print the event.

// open a device
struct libevdev *dev = NULL;
int fd;
int rc = 1;
 
fd = open("/dev/input/event0", O_RDONLY|O_NONBLOCK);
rc = libevdev_new_from_fd(fd, &dev);
if (rc < 0) {
        fprintf(stderr, "Failed to init libevdev (%s)\n", strerror(-rc));
        exit(1);
}
// print the device info
printf("Input device name: \"%s\"\n", libevdev_get_name(dev));
printf("Input device ID: bus %#x vendor %#x product %#x\n",
       libevdev_get_id_bustype(dev),
       libevdev_get_id_vendor(dev),
       libevdev_get_id_product(dev));
// hecks for relative axes and a left mouse button
if (!libevdev_has_event_type(dev, EV_REL) ||
    !libevdev_has_event_code(dev, EV_KEY, BTN_LEFT)) {
        printf("This device does not look like a mouse\n");
        exit(1);
}
 
 // monitors the device to print the event
do {
        struct input_event ev;
        rc = libevdev_next_event(dev, LIBEVDEV_READ_FLAG_NORMAL, &ev);
        if (rc == 0)
                printf("Event: %s %s %d\n",
                       libevdev_event_type_get_name(ev.type),
                       libevdev_event_code_get_name(ev.type, ev.code),
                       ev.value);
} while (rc == 1 || rc == 0 || rc == -EAGAIN);