【Zhengdian Atom Rockchip RV1126 Review】 5 input subsystem

damiaa

【Zhengdian Atom Rockchip RV1126 Review】 5 input subsystem [Copy link]

 

【Review of the 5-input subsystem】

1. Introduction to input subsystem

The input subsystem in Linux is a device framework for managing different types of input devices, including the input driver layer, input core layer, and input event processing layer, providing a unified interface for applications to access these devices.

The Input subsystem supports multiple types of input devices, such as keyboards, mice, touch screens, game controllers, sensors, etc., but they allow user space applications and device drivers to interact with input devices through a unified interface and framework to obtain and process input data.

2. Let’s talk about the input subsystem of the RV1126 development board and do some experiments.

There are four buttons on the board, which are implemented by the input subsystem.

We can plug in the mouse and buttons to view the mouse and button events in the input subsystem.

The Linux system manages input devices (buttons, mouse, touch screen, game joystick, etc.) through the input subsystem. After the corresponding driver is installed and connected to the corresponding interface ( USB device should be plugged into the USB device port), the system will generate the corresponding device in / dev / input / , as shown below:

You can also see the following information in / proc/bus/input :

When there is no mouse or keyboard plugged in, it looks like this:

Plug in the mouse and keyboard as follows:

When an event occurs on the input device, the kernel reports the event to the device file. The event data is stored in the device file in the unit of struct input_event . This structure is used to read the event data : /linux/input.h

struct input_event {

struct timeval time; //The time when the event occurred

__u16 type; //Event type

__u16 code; //Event code

__s32 value; //Event value

};

The application only needs to care about the content of this structure.

/*

* There are many types of Event

*/

#define EV_SYN0x00

#define EV_KEY0x01

#define EV_REL0x02

#define EV_ABS0x03

#define EV_MSC0x04

#define EV_SW0x05

#define EV_LED0x11

#define EV_SND0x12

#define EV_REP0x14

#define EV_FF0x15

#define EV_PWR0x16

#define EV_FF_STATUS0x17

#define EV_MAX0x1f

#define EV_CNT(EV_MAX+1)

For example, the keyboard event type EV_KEY

The event code describes the event more specifically, such as the value of a keyboard key (which key), the position of a mouse, the information of a scroll wheel, and the position of a touch screen.

Value describes the event in more detail, such as whether a button is pressed or released, the x and y values of the mouse, several values of the touch screen, etc.

We will now use a test program to demonstrate the event situation.

1. Plug in a wireless keyboard and mouse (I have a two-in-one, but anything will do, as long as it’s a keyboard and mouse).

2. Cross-compile the following example program, push it to the board using adb, and modify the execution properties.

/* 
 * Copyright 2002 Red Hat Inc., Durham, North Carolina. 
 * 
 * All Rights Reserved. 
 * 
 * Permission is hereby granted, free of charge, to any person obtaining 
 * a copy of this software and associated documentation files (the 
 * "Software"), to deal in the Software without restriction, including 
 * without limitation on the rights to use, copy, modify, merge, 
 * publish, distribute, sublicense, and/or sell copies of the Software, 
 * and to permit persons to whom the Software is furnished to do so, 
 * subject to the following conditions: 
 * 
 * The above copyright notice and this permission notice (including the 
 * next paragraph) shall be included in all copies or substantial 
 * portions of the Software. 
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF 
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND 
 * NON-INFRINGEMENT.  IN NO EVENT SHALL RED HAT AND/OR THEIR SUPPLIERS 
 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN 
 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN 
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE 
 * SOFTWARE. 
 * 
 * This is a simple test program that reads from /dev/input/event*, 
 * decoding events into a human readable form. 
 */  

/* 
 * Authors: 
 *   Rickard E. (Rik) Faith <faith@redhat.com> 
 * 
 */ 

#include <stdio.h>  
#include <stdlib.h>  
#include <unistd.h>  
#include <string.h>  
#include <sys/types.h>  
#include <fcntl.h>  
#include <errno.h>  
#include <time.h>  
#include <linux/input.h>  

struct input_event event;  

int main(int argc, char **argv)  
{  
    char          name[64];           /* RATS: Use ok, but could be better */  
    char          buf[256] = { 0, };  /* RATS: Use ok */  
    unsigned char mask[EV_MAX/8 + 1]; /* RATS: Use ok */  
    int           version;  
    int           fd = 0;  
    int           rc;  
    int           i, j;  
    char          *tmp;  

#define test_bit(bit) (mask[(bit)/8] & (1 << ((bit)%8)))  

    for (i = 0; i < 32; i++) {  
        sprintf(name, "/dev/input/event%d", i);  
        if ((fd = open(name, O_RDONLY, 0)) >= 0) {  
            ioctl(fd, EVIOCGVERSION, &version);  
            ioctl(fd, EVIOCGNAME(sizeof(buf)), buf);  
            ioctl(fd, EVIOCGBIT(0, sizeof(mask)), mask);  
            printf("%s\n", name);  
            printf("    evdev version: %d.%d.%d\n",  
                   version >> 16, (version >> 8) & 0xff, version & 0xff);  
            printf("    name: %s\n", buf);  
            printf("    features:");  
            for (j = 0; j < EV_MAX; j++) {  
                if (test_bit(j)) {  
                    const char *type = "unknown";  
                    switch(j) {  
                    case EV_KEY: type = "keys/buttons"; break;  
                    case EV_REL: type = "relative";     break;  
                    case EV_ABS: type = "absolute";     break;  
                    case EV_MSC: type = "reserved";     break;  
                    case EV_LED: type = "leds";         break;  
                    case EV_SND: type = "sound";        break;  
                    case EV_REP: type = "repeat";       break;  
                    case EV_FF:  type = "feedback";     break;  
                    }  
                    printf(" %s", type);  
                }  
            }  
            printf("\n");  
            close(fd);  
        }  
    }  

    if (argc > 1) {  
        sprintf(name, "/dev/input/event%d", atoi(argv[1]));  
        if ((fd = open(name, O_RDWR, 0)) >= 0) {  
            printf("%s: open, fd = %d\n", name, fd);  
            for (i = 0; i < LED_MAX; i++) {  
                event.time.tv_sec  = time(0);  
                event.time.tv_usec = 0;  
                event.type         = EV_LED;  
                event.code         = i;  
                event.value        = 0;  
                write(fd, &event, sizeof(event));  
            }  

            while ((rc = read(fd, &event, sizeof(event))) > 0) {  
                printf("%-24.24s.%06lu type 0x%04x; code 0x%04x;"  
                       " value 0x%08x; ",  
                       ctime(&event.time.tv_sec),  
                       event.time.tv_usec,  
                       event.type, event.code, event.value);  
                switch (event.type) {  
                case EV_KEY:  
                    if (event.code > BTN_MISC) {  
                        printf("Button %d %s",  
                               event.code & 0xff,  
                               event.value ? "press" : "release");  
                    } else {  
                        printf("Key %d (0x%x) %s",  
                               event.code & 0xff,  
                               event.code & 0xff,  
                               event.value ? "press" : "release");  
                    }  
                    break;  
                case EV_REL:  
                    switch (event.code) {  
                    case REL_X:      tmp = "X";       break;  
                    case REL_Y:      tmp = "Y";       break;  
                    case REL_HWHEEL: tmp = "HWHEEL";  break;  
                    case REL_DIAL:   tmp = "DIAL";    break;  
                    case REL_WHEEL:  tmp = "WHEEL";   break;  
                    case REL_MISC:   tmp = "MISC";    break;  
                    default:         tmp = "UNKNOWN"; break;  
                    }  
                    printf("Relative %s %d", tmp, event.value);  
                    break;  
                case EV_ABS:  
                    switch (event.code) {  
                    case ABS_X:        tmp = "X";        break;  
                    case ABS_Y:        tmp = "Y";        break;  
                    case ABS_Z:        tmp = "Z";        break;  
                    case ABS_RX:       tmp = "RX";       break;  
                    case ABS_RY:       tmp = "RY";       break;  
                    case ABS_RZ:       tmp = "RZ";       break;  
                    case ABS_THROTTLE: tmp = "THROTTLE"; break;  
                    case ABS_RUDDER:   tmp = "RUDDER";   break;  
                    case ABS_WHEEL:    tmp = "WHEEL";    break;  
                    case ABS_GAS:      tmp = "GAS";      break;  
                    case ABS_BRAKE:    tmp = "BRAKE";    break;  
                    case ABS_HAT0X:    tmp = "HAT0X";    break;  
                    case ABS_HAT0Y:    tmp = "HAT0Y";    break;  
                    case ABS_HAT1X:    tmp = "HAT1X";    break;  
                    case ABS_HAT1Y:    tmp = "HAT1Y";    break;  
                    case ABS_HAT2X:    tmp = "HAT2X";    break;  
                    case ABS_HAT2Y:    tmp = "HAT2Y";    break;  
                    case ABS_HAT3X:    tmp = "HAT3X";    break;  
                    case ABS_HAT3Y:    tmp = "HAT3Y";    break;  
                    case ABS_PRESSURE: tmp = "PRESSURE"; break;  
                    case ABS_DISTANCE: tmp = "DISTANCE"; break;  
                    case ABS_TILT_X:   tmp = "TILT_X";   break;  
                    case ABS_TILT_Y:   tmp = "TILT_Y";   break;  
                    case ABS_MISC:     tmp = "MISC";     break;  
					case ABS_MT_SLOT:  tmp = "MT_SLOT";     break;  
					case ABS_MT_TRACKING_ID: tmp = "MT_TRACKING_ID";     break;  
					case ABS_MT_POSITION_X:  tmp = "MT_X";     break;  
					case ABS_MT_POSITION_Y:  tmp = "MT_Y";     break;  
                    default:           tmp = "UNKNOWN";  break;  
                    }  
                    printf("Absolute %s %d", tmp, event.value);  
                    break;  
                case EV_MSC: printf("Misc"); break;  
                case EV_LED: printf("Led");  break;  
                case EV_SND: printf("Snd");  break;  
                case EV_REP: printf("Rep");  break;  
                case EV_FF:  printf("FF");   break;  
                    break;  
                }  
                printf("\n");  
            }  
            printf("rc = %d, (%s)\n", rc, strerror(errno));  
            close(fd);  
        }  
    }  
    return 0;  
}

3. Run ./inputeventtest to see the prompts:

4. Run ./inputeventtest 1 to test the yellow row of keys and observe the printed data.

5. Run ./inputeventtest 2 to test pressing keyboard keys and observe the printed data.

6. Run ./inputeventtest 3 to test the mouse (left click, right click, scroll wheel, etc.) and observe the printed data.

At this point, we have a clearer understanding of the application of input.

Demo Video

a

Thank you everyone, see you next time.

LitchiCheng

Then you can make a custom handle application based on this, non-bus type

damiaa

LitchiCheng posted on 2024-2-18 09:31 Then you can make a custom handle application based on this, non-bus type

Input is really powerful, and most input applications should be able to use it.