When it comes to using USB peripherals with your Linux system, you may wonder where the input events from non-mouse/keyboard devices are sent. Whether it's a game controller, a joystick, or any other USB device, Linux has a mechanism in place to handle input events from these peripherals.
In Linux, input events from non-mouse/keyboard USB peripherals are sent to the /dev/input directory. This directory acts as a hub for all input devices connected to your system, including both traditional and non-traditional input devices.
Within the /dev/input directory, each input device is represented by a separate file. These files are named in the following format: eventX, where X is a number assigned to each input device. For example, event0 represents the first input device, event1 represents the second input device, and so on.
Now that you know where the input events are sent, you might be wondering how to access and utilize them. The good news is that Linux provides a variety of tools and libraries to make it easy for developers to work with input events from non-mouse/keyboard USB peripherals.
One popular library for handling input events in Linux is libevdev. This library provides a simple and efficient API for reading and interpreting input events from various devices. It abstracts the low-level details of handling input events and allows developers to focus on their application logic.
To use libevdev, you first need to open the input device file located in /dev/input. This can be done using the open() system call in C or the equivalent function in your preferred programming language. Once the device file is open, you can create a libevdev device using the libevdev_new_from_fd() function.
#include <libevdev/libevdev.h>
int main() {
int fd = open("/dev/input/eventX", O_RDONLY);
struct libevdev *dev = NULL;
if (fd < 0) {
printf("Failed to open input device
");
return -1;
}
int err = libevdev_new_from_fd(fd, &dev);
if (err < 0) {
printf("Failed to create libevdev device
");
return -1;
}
// Now you can start reading and interpreting input events
// using libevdev functions
libevdev_free(dev);
close(fd);
return 0;
}
Once you have a libevdev device, you can start reading input events using functions like libevdev_next_event(). This function retrieves the next input event from the device and provides you with information such as the event type, event code, and event value.
With this information, you can handle the input events according to your application's needs. For example, if you're building a game, you can map joystick movements to in-game actions or control the game using a game controller.
It's important to note that the specific handling of input events may vary depending on the type of USB peripheral you're using. Each device may have its own set of event codes and values, so you'll need to consult the device's documentation or specific programming guides for accurate interpretation.
Overall, Linux provides a robust infrastructure for handling input events from non-mouse/keyboard USB peripherals. The /dev/input directory acts as a central hub for these devices, and libraries like libevdev simplify the process of reading and interpreting input events. With the right tools and resources, you can make the most out of your USB peripherals in Linux.
References
| Source | Link |
|---|---|
| libevdev documentation | https://www.freedesktop.org/software/libevdev/doc/latest/ |
| Linux Input Subsystem Documentation | https://www.kernel.org/doc/html/latest/input/ |