嵌入式Linux—输入子系统

输入系统

常见的输入设备有键盘、鼠标、遥控杆、书写板、触摸屏等等,用户通过这些输入设备与Linux系统进行数据交换。

内核中怎样表示一个输入设备

// include/linux/input.h
struct input_dev {
	const char *name;  //设备名称
	const char *phys;  //设备物理路径
	const char *uniq;  //设备唯一标识码
	struct input_id id;

	unsigned long propbit[BITS_TO_LONGS(INPUT_PROP_CNT)];

	unsigned long evbit[BITS_TO_LONGS(EV_CNT)];   //支持什么类型的输入事件
	unsigned long keybit[BITS_TO_LONGS(KEY_CNT)]; //支持按键输入事件的话,支持哪些按键(键盘)
	unsigned long relbit[BITS_TO_LONGS(REL_CNT)]; //支持相对位移事件的话,支持哪些
	unsigned long absbit[BITS_TO_LONGS(ABS_CNT)];
	unsigned long mscbit[BITS_TO_LONGS(MSC_CNT)];
	unsigned long ledbit[BITS_TO_LONGS(LED_CNT)];
	unsigned long sndbit[BITS_TO_LONGS(SND_CNT)];
	unsigned long ffbit[BITS_TO_LONGS(FF_CNT)];
	unsigned long swbit[BITS_TO_LONGS(SW_CNT)];
	
	.......
	
	};

查看所有的输入设备:

ls /dev/input/* -l

查看输入设备的信息:

cat /proc/bus/input/devices

得到如下信息:

[root@imx6ull:~]# cat /proc/bus/input/devices
I: Bus=0019 Vendor=0000 Product=0000 Version=0000
N: Name="20cc000.snvs:snvs-powerkey"
P: Phys=snvs-pwrkey/input0
S: Sysfs=/devices/soc0/soc/2000000.aips-bus/20cc000.snvs/20cc000.snvs:snvs-powerkey/input/input0
U: Uniq=
H: Handlers=kbd event0 evbug
B: PROP=0
B: EV=3
B: KEY=100000 0 0 0

I: Bus=0018 Vendor=dead Product=beef Version=28bb  //设备ID(定义在input.h的struct input_id结构体)
N: Name="goodix-ts"      //名称
P: Phys=input/ts         //物理地址
S: Sysfs=/devices/virtual/input/input1  //sys系统地址
U: Uniq=          //标识号(无)
H: Handlers=event1 evbug
B: PROP=2        //设备属性
B: EV=b          //支持何种输入事件 
B: KEY=1c00 0 0 0 0 0 0 0 0 0 0   //设备具有的键
B: ABS=6e18000 0

I: Bus=0019 Vendor=0001 Product=0001 Version=0100
N: Name="gpio-keys"
P: Phys=gpio-keys/input0
S: Sysfs=/devices/soc0/gpio-keys/input/input2
U: Uniq=
H: Handlers=kbd event2 evbug
B: PROP=0
B: EV=3
B: KEY=c

APP可以获得什么数据

// include/linux/input.h
struct input_value {
	__u16 type;   //当前数据的事件类型
	__u16 code;   //当前事件类型下的哪一个事件
	__s32 value;  //
};

Type的内容:

// include/uapi/linux/input-event-codes.h
/*
 * Event types
 */

#define EV_SYN			0x00  //同步事件
#define EV_KEY			0x01  //键盘事件
#define EV_REL			0x02  //相对位移事件
#define EV_ABS			0x03  //绝对位移事件
#define EV_MSC			0x04
#define EV_SW			0x05
#define EV_LED			0x11
#define EV_SND			0x12
#define EV_REP			0x14
#define EV_FF			0x15
#define EV_PWR			0x16
#define EV_FF_STATUS		0x17
#define EV_MAX			0x1f
#define EV_CNT			(EV_MAX+1)

code的内容(以EV_KEY举例)

// include/uapi/linux/input-event-codes.h
#define KEY_RESERVED		0
#define KEY_ESC			1
#define KEY_1			2
#define KEY_2			3
#define KEY_3			4
#define KEY_4			5
#define KEY_5			6
#define KEY_6			7
#define KEY_7			8
#define KEY_8			9
#define KEY_9			10
#define KEY_0			11

获取输入设备信息实例

两个ioctl的request参数说明(input.h)
request 说明
EVIOCGID 返回输入设备ID
EVIOCGBIT(ev,len) 获取输入设备支持的事件类型列表

ev值的说明:ev参数表示要获取的事件类型,它是一个整数值

  • 当ev=0,表示要获取输入设备支持的所有事件类型列表,包括键盘事件、鼠标事件、相对事件、绝对事件、事件同步、杂项事件等。
  • 当ev=1,表示要获取输入设备支持的键盘事件类型列表。
  • 当ev=2,表示要获取输入设备支持的相对事件类型列表。

EVIOCGBIT的iotcl调用说明:必须使用

len = ioctl(fd, EVIOCGBIT(0, sizeof(evbit)), evbit);    
//len是evbit的实际读取大小,如果单独使用sizeof(evbit)得到len,将发生段错误
源码:
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>
#include <sys/ioctl.h>
#include <linux/input.h>

/* 用法:./get_input_info /dev/input/event0 */
int main(int argc, char const **argv)
{
	int fd;
	struct input_id id;
	int err;
	unsigned char byte;
	unsigned int evbit[2];
	int i;
	int bit;
	unsigned int len;
	char *ev_names[] = {
		"EV_SYN ",
		"EV_KEY ",
		"EV_REL ",
		"EV_ABS ",
		"EV_MSC ",
		"EV_SW	",
		"NULL ",
		"NULL ",
		"NULL ",
		"NULL ",
		"NULL ",
		"NULL ",
		"NULL ",
		"NULL ",
		"NULL ",
		"NULL ",
		"NULL ",
		"EV_LED ",
		"EV_SND ",
		"NULL ",
		"EV_REP ",
		"EV_FF	",
		"EV_PWR ",
	};

	if(argc != 2) 
	{
		printf("Usage: %s <dev>\n", argv[0]);
		return -1;
	}
	fd = open(argv[1], O_RDWR);
	if(fd == -1) 
	{
		printf("can not open %s\n", argv[1]);
		return -1;
	}
	err = ioctl(fd, EVIOCGID, &id);      //返回输入设备ID
	if(err == 0)
	{
		printf("bustype = 0x%x\n", id.bustype );
		printf("vendor	= 0x%x\n", id.vendor  );
		printf("product = 0x%x\n", id.product );
		printf("version = 0x%x\n", id.version );
	}
	len = ioctl(fd, EVIOCGBIT(0,sizeof(evbit)), evbit);   //返回输入事件类型
	printf("support ev type:\n");
	for(i = 0;i < len;i++)
	{
		byte = ((unsigned char *)evbit)[i];
		for(bit = 0;bit < 8;bit++)
		{
			if(byte & (1<<bit))
			{
				printf("%s \n", ev_names[i*8 + bit]);
			}
		}

	}
	return 0;

}

实验结果:
[root@imx6ull:/mnt]# ./get_input_info /dev/input/event0
bustype = 0x19
vendor  = 0x0
product = 0x0
version = 0x0
support ev type:
EV_SYN
EV_KEY
[root@imx6ull:/mnt]# ./get_input_info /dev/input/event1
bustype = 0x18
vendor  = 0xdead
product = 0xbeef
version = 0x28bb
support ev type:
EV_SYN
EV_KEY
EV_ABS
[root@imx6ull:~]# cat /proc/bus/input/devices
I: Bus=0019 Vendor=0000 Product=0000 Version=0000
N: Name="20cc000.snvs:snvs-powerkey"
P: Phys=snvs-pwrkey/input0
S: Sysfs=/devices/soc0/soc/2000000.aips-bus/20cc000.snvs/20cc000.snvs:snvs-powerkey/input/input0
U: Uniq=
H: Handlers=kbd event0 evbug
B: PROP=0
B: EV=3
B: KEY=100000 0 0 0

I: Bus=0018 Vendor=dead Product=beef Version=28bb
N: Name="goodix-ts"
P: Phys=input/ts
S: Sysfs=/devices/virtual/input/input1
U: Uniq=
H: Handlers=event1 evbug
B: PROP=2
B: EV=b
B: KEY=1c00 0 0 0 0 0 0 0 0 0 0
B: ABS=6e18000 0

I: Bus=0019 Vendor=0001 Product=0001 Version=0100
N: Name="gpio-keys"
P: Phys=gpio-keys/input0
S: Sysfs=/devices/soc0/gpio-keys/input/input2
U: Uniq=
H: Handlers=kbd event2 evbug
B: PROP=0
B: EV=3
B: KEY=c

结论:EV值与程序输出的type结果一致

查询和休眠唤醒方式读输入事件

所谓的阻塞与非阻塞,是在open处声明。当设置为阻塞方式,如果没有输入事件,整个进程都在阻塞态

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>
#include <sys/ioctl.h>
#include <linux/input.h>
#include <unistd.h>
#include <string.h>


/* 用法:./get_input_info /dev/input/event0 */
int main(int argc, char const **argv)
{
	int fd;
	unsigned int len;
	struct input_event event;   //read读到的是input_event类型的结构体

	if(argc < 2) 
	{
		printf("Usage: %s <dev> [noblock]\n", argv[0]);
		return -1;
	}
	if(argc == 3 && !strcmp(argv[2], "noblock"))
	{
		fd = open(argv[1], O_RDWR | O_NONBLOCK);  //非阻塞(查询)
	}
	else
	{
		fd = open(argv[1], O_RDWR);
	}
	if(fd == -1) 
	{
		printf("can not open %s\n", argv[1]);
		return -1;
	}

	while(1)
	{
		len = read(fd, &event, sizeof(event));     //阻塞方式下,进程阻塞在此
		if(len == sizeof(event))
		{
			printf("type = 0x%x, code = 0x%x, value = 0x%x", event.type, event.code, event.value);
		}
		else
		{
			printf("read err %d", len);
		}
	}
	return 0;

}

实验现象:
  • 查询方式(非阻塞):反复查询,输出"read err",直到操作输入设备时,输出内容更改为输入事件内容
  • 休眠-唤醒方式(阻塞):只有操作屏幕,才会输出事件内容

POLL方式读输入事件

poll会在设定的时间内进行监听,当改时间内有输入事件返回或超过设定时间没有事件返回,poll都将唤醒。poll/select函数可以监测多个文件,可以监测多种事件。

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>
#include <sys/ioctl.h>
#include <linux/input.h>
#include <unistd.h>
#include <string.h>
#include <poll.h>


/* 用法:./get_input_info /dev/input/event0 */
int main(int argc, char const **argv)
{
	int fd;
	struct input_event event;   //read读到的是input_event类型的结构体
	struct pollfd pollfd;
	nfds_t nfds = 1;      //同时打开一个文件

	if(argc != 2) 
	{
		printf("Usage: %s <dev>\n", argv[0]);
		return -1;
	}
	fd = open(argv[1], O_RDWR | O_NONBLOCK);  //非阻塞(查询)
	if(fd == -1) 
	{
		printf("can not open %s\n", argv[1]);
		return -1;
	}
	while(1)
	{
		pollfd.fd = fd;
		pollfd.events = POLLIN;
		pollfd.revents = 0;     //revents初始化为0,当有输入事件传入,内核改写revents
		poll(&pollfd, nfds, 3000);    //poll等待时间为3s
		if(pollfd.revents == POLLIN)      //只有poll函数返回了数据,才调用read
		{
			while(read(fd, &event, sizeof(event)) == sizeof(event))    //把一次获取到的数据读完再退出
			{
				printf("type = 0x%x, code = 0x%x, value = 0x%x\n", event.type, event.code, event.value);
			}
		}
		else if(pollfd.revents == 0)
		{
			printf("time out\n");
		}
		else
		{
			printf("read err\n");
		}
	}
	return 0;

}
关于POLL实现多路复用IO
struct pollfd pollfd[n];    //n为文件个数
nfds_t nfds = n;      //同时打开n个文件

.......

if(pollfd[0].revents == POLLIN){}     //依次访问revents
if(pollfd[1].revents == POLLIN){}

.......

异步通知方式读输入事件

[补充]fcntl的五个功能:

  • 复制一个现有的描述符(cmd=F_DUPFD).
  • 获得/设置文件描述符标记(cmd=F_GETFD或F_SETFD).
  • 获得/设置文件状态标记(cmd=F_GETFL或F_SETFL).
  • 获得/设置异步I/O所有权(cmd=F_GETOWN或F_SETOWN).
  • 获得/设置记录锁(cmd=F_GETLK , F_SETLK或F_SETLKW).
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdio.h>
#include <sys/ioctl.h>
#include <linux/input.h>
#include <unistd.h>
#include <string.h>
#include <signal.h>

int fd;

void sig_func(int sig)
{
	struct input_event event;
	while(read(fd, &event, sizeof(event)) == sizeof(event))
	{
		printf("type = 0x%x, code = 0x%x, value = 0x%x\n", event.type, event.code, event.value);
	}
}


/* 用法:./get_input_info /dev/input/event0 */
int main(int argc, char const **argv)
{	
	int count = 0;
	unsigned short flag;
	if(argc != 2) 
	{
		printf("Usage: %s <dev>\n", argv[0]);
		return -1;
	}
	signal(SIGIO, sig_func);   //1.注册信号处理函数(信号类型为IO类型)
	fd = open(argv[1], O_RDWR | O_NONBLOCK);  //2.打开驱动(一定要用非阻塞方式,否则无输入事件进程一直被阻塞)
	if(fd == -1) 
	{
		printf("can not open %s\n", argv[1]);
		return -1;
	}
	fcntl(fd ,F_SETOWN, getpid());   //3.告知驱动程序app进程ID
	flag = fcntl(fd, F_GETFL);       //4.获得文件状态标记
	fcntl(fd, F_SETFL, flag | FASYNC); //5.设置文件状态标记(将进程添加到驱动fasync事件等待队列)
	
	while(1)
	{
		printf("count = %d\n", count++);
		sleep(2);
	}
	return 0;

}

实验结果:
[root@imx6ull:/mnt]# ./get_input_info /dev/input/event1
count = 0
count = 1
count = 2               //无输入事件时正常计数
type = 0x3, code = 0x39, value = 0x6
type = 0x3, code = 0x35, value = 0x1a6
type = 0x3, code = 0x36, value = 0x131
type = 0x3, code = 0x30, value = 0x1f
type = 0x3, code = 0x3a, value = 0x1f
type = 0x1, code = 0x14a, value = 0x1
type = 0x0, code = 0x0, value = 0x0
count = 3
type = 0x3, code = 0x35, value = 0x1a7
type = 0x0, code = 0x0, value = 0x0
count = 4
type = 0x3, code = 0x35, value = 0x1a9
type = 0x0, code = 0x0, value = 0x0
count = 5
type = 0x3, code = 0x35, value = 0x1a8
type = 0x0, code = 0x0, value = 0x0
count = 6

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