Linux /dev/uinput

1. 简介

    uinput可在以下情况大显身手：

    1) 不需要自己写驱动

     2) 用户态向/dev/input/eventX写入事件，即用户向Kernel注入数据

2. 使用流程

2.1 打开UInput Device

APP：

char *dev = "/dev/uinput“;
open(dev, O_WRONLY | O_NDELAY);

Kernel：

     static int uinput_open(struct inode *inode, struct file *file)
    参数inode对应的是 主设备为10,子设备为223的node(即位用户态的dev)
    参数file对应打开的文件。
    动作：
       创建了newdev-- uinput_device结构。
       newdev->state = UIST_NEW_DEVICE; 
       file->private_data = newdev;
 
 

2.2 设置UInput Device

APP:    

    ioctl(fd, UI_SET_EVBIT, EV_KEY);

Kernel：
     static long uinput_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
      参数file对应打开的文件。
      参数cmd 对应用户态ioctl参数2。UI_SET_EVBIT
      参数arg对应用户态ioctl参数3。EV_KEY
   动作：
      将driver参数传递过来。
      udev = file->private_data;
      udev->dev 是个input_dev 类型数据。 此时，它未初始化。
      如果udev->dev为空，则使用 uinput_allocate_device(udev);申请input_dev结构
 
    具体到CMD=UI_SET_EVBIT
       uinput_set_bit(arg, evbit, EV_MAX);
       首先判断newdev->state为UIST_CREATED，则返回错误码。
       这就说明：设置bit，需要在create input device 之前。
       具体动作为：udev->dev->evbit 设为EV_KEY.
 
注意：此处input device的evbit:
      一个是evbit表示设备所支持的动作.:
      #define EV_KEY   0x01  // 按键
      #define EV_REL   0x02  // 释放
 

    其它设置如下:
    ret = ioctl(fd, UI_SET_RELBIT, REL_X); //鼠标
    ret = ioctl(fd, UI_SET_RELBIT, REL_Y);
    ret = ioctl(fd, UI_SET_EVBIT, EV_ABS);
    ret = ioctl(fd, UI_SET_ABSBIT, ABS_X);
    ret = ioctl(fd, UI_SET_ABSBIT, ABS_Y);
    ret = ioctl(fd, UI_SET_ABSBIT, ABS_PRESSURE);
    以上设置了Input Device关心或者说会产生的消息。
 

 2.3 写入设备信息

APP: 

struct uinput_user_dev uinput;
uinput.id.version = 4;
uinput.id.bustype = BUS_USB;
uinput.absmin[ABS_X] = 0;
uinput.absmax[ABS_X] = 65535; //sam 把屏幕设为0-65535
uinput.absmin[ABS_Y] = 0;
uinput.absmax[ABS_Y] = 65535;
uinput.absmin[ABS_PRESSURE] = 0;
uinput.absmax[ABS_PRESSURE] = 0xfff;
ret = write(fd, &uinput, sizeof(uinput));

Kernel:

      Device status为UIST_NEW_DEVICE
     并将udev->dev 这个input device 具体化。初始化该input_dev,之后，改变状态：
     udev->state = UIST_SETUP_COMPLETE;

2.4 创建Input Device

APP:   

   注意，此处是创建了Input Device。而不是UInput Device。
      ioctl(fd, UI_DEV_CREATE)；
 Kernel：
     input_register_device(udev->dev); //向子系统注册该设备，之后中断时input_event（）向子系统报告事件
     udev->state = UIST_CREATED;
 

2.5 向Input Device发送Event

APP:

 struct input_event event = {0};
 gettimeofday(&event.time, NULL);
 event.type  = EV_KEY;
 event.code  = key;
 event.value = press ? 1:0;
 write(fd, &event, sizeof(event));

Kernel:
     static ssize_t uinput_write(struct file *file, const char __user *buffer, size_t count, loff_t *ppos)
     因为此时state为UIST_CREATED
     input_event(udev->dev, ev.type, ev.code, ev.value);    // 发送event.
 

 3. 总结

使用UInput的步骤为：
1. 打开设备。
2. 使用ioctl() 配置设备。
3. 使用write() 将input device信息设置好。
4. 使用ioctl(UI_DEV_CREATE)创建Input Device。（即使用write设置的）
5. 再使用write() 写入event.

4. 实例

/* Globals */ 
static int uinp_fd = -1; 
struct uinput_user_dev uinp; // uInput device structure 
struct input_event event; // Input device structure 
/* Setup the uinput device */ 
int setup_uinput_device() 
{ 
   // Temporary variable 
   int i=0; 
   
   // Open the input device 
   uinp_fd = open("/dev/uinput", O_WRONLY | O_NDELAY); 
   if (uinp_fd == NULL) 
   { 
      Dashboard January 2007 Issue 
      printf("Unable to open /dev/uinput/n"); 
      return -1; 
   } 
   
   memset(&uinp,0,sizeof(uinp)); // Intialize the uInput device to NULL 
   strncpy(uinp.name, "PolyVision Touch Screen", UINPUT_MAX_NAME_SIZE); 
   uinp.id.version = 4; 
   uinp.id.bustype = BUS_USB; 
   
   // Setup the uinput device 
   ioctl(uinp_fd, UI_SET_EVBIT, EV_KEY); 
   ioctl(uinp_fd, UI_SET_EVBIT, EV_REL); 
   ioctl(uinp_fd, UI_SET_RELBIT, REL_X); 
   ioctl(uinp_fd, UI_SET_RELBIT, REL_Y); 
   for (i=0; i < 256; i++) { 
      ioctl(uinp_fd, UI_SET_KEYBIT, i); 
   } 
   
   ioctl(uinp_fd, UI_SET_KEYBIT, BTN_MOUSE); 
   ioctl(uinp_fd, UI_SET_KEYBIT, BTN_TOUCH); 
   ioctl(uinp_fd, UI_SET_KEYBIT, BTN_MOUSE); 
   ioctl(uinp_fd, UI_SET_KEYBIT, BTN_LEFT); 
   ioctl(uinp_fd, UI_SET_KEYBIT, BTN_MIDDLE); 
   ioctl(uinp_fd, UI_SET_KEYBIT, BTN_RIGHT); 
   ioctl(uinp_fd, UI_SET_KEYBIT, BTN_FORWARD); 
   ioctl(uinp_fd, UI_SET_KEYBIT, BTN_BACK); 
   
   /* Create input device into input sub-system */ 
   write(uinp_fd, &uinp, sizeof(uinp)); 
   if (ioctl(uinp_fd, UI_DEV_CREATE)) 
   { 
      printf("Unable to create UINPUT device."); 
      return -1; 
   } 
   return 1; 
} 

void send_click_events( ) 
{ 
   // Move pointer to (100,100) location 
   memset(&event, 0, sizeof(event)); 
   gettimeofday(&event.time, NULL); 
   event.type = EV_REL; 
   event.code = REL_X; 
   event.value = 100; 
   write(uinp_fd, &event, sizeof(event)); 

   event.type = EV_REL; 
   event.code = REL_Y; 
   event.value = 100; 
   write(uinp_fd, &event, sizeof(event)); 

   event.type = EV_SYN; 
   event.code = SYN_REPORT; 
   event.value = 0; 
   write(uinp_fd, &event, sizeof(event)); 

   // Report BUTTON CLICK - PRESS event 
   memset(&event, 0, sizeof(event)); 
   gettimeofday(&event.time, NULL); 
   event.type = EV_KEY; 
   event.code = BTN_LEFT; 
   event.value = 1; 
   write(uinp_fd, &event, sizeof(event)); 
   
   event.type = EV_SYN; 
   event.code = SYN_REPORT; 
   event.value = 0; 
   write(uinp_fd, &event, sizeof(event)); 
   
   // Report BUTTON CLICK - RELEASE event 
   memset(&event, 0, sizeof(event)); 
   gettimeofday(&event.time, NULL); 
   event.type = EV_KEY; 
   event.code = BTN_LEFT; 
   event.value = 0; 
   
   write(uinp_fd, &event, sizeof(event)); 
   event.type = EV_SYN; 
   event.code = SYN_REPORT; 
   event.value = 0; 
   write(uinp_fd, &event, sizeof(event)); 
} 

void send_a_button() 
{ 
   // Report BUTTON CLICK - PRESS event 
   memset(&event, 0, sizeof(event)); 
   gettimeofday(&event.time, NULL); 
   event.type = EV_KEY; 
   event.code = KEY_A; 
   event.value = 1; 
   write(uinp_fd, &event, sizeof(event)); 
   
   event.type = EV_SYN; 
   event.code = SYN_REPORT; 
   event.value = 0; 
   write(uinp_fd, &event, sizeof(event)); 
   
   // Report BUTTON CLICK - RELEASE event 
   memset(&event, 0, sizeof(event)); 
   gettimeofday(&event.time, NULL); 
   event.type = EV_KEY; 
   event.code = KEY_A; 
   event.value = 0; 
   
   write(uinp_fd, &event, sizeof(event)); 
   event.type = EV_SYN; 
   event.code = SYN_REPORT; 
   event.value = 0; 
   write(uinp_fd, &event, sizeof(event)); 
} 

/* This function will open the uInput device. Please make 
sure that you have inserted the uinput.ko into kernel. */ 
int main() 
{ 
   // Return an error if device not found. 
   if (setup_uinput_device() < 0) 
   { 
   printf("Unable to find uinput device/n"); 
   return -1; 
   } 
   
   send_a_button(); // Send a "A" key 
   send_click_events(); // Send mouse event 
   
   /* Destroy the input device */ 
   ioctl(uinp_fd, UI_DEV_DESTROY); 
   
   /* Close the UINPUT device */ 
   close(uinp_fd); 
}

 
 
 
UInput添加的Input Device在/proc的反应：
#cat /proc/bus/input/device
I: Bus=0003 Vendor=0000 Product=0000 Version=0004
N: Name="uinput"
P: Phys=
S: Sysfs=/class/input/input6
H: Handlers=event1 mouse1
B: EV=f
B: KEY=400 0 670000 ffff ffffffff ffffffff ffffffff ffffffff ffffffff ffffffff ffffffff
B: REL=3
B: ABS=1000003
解释如下：
Bus=0003 Vendor=0000 Product=0000 Version=0004
这是在第一次write时设置的：
uinp.id.version = 4;
uinp.id.bustype = BUS_USB;
struct input_id {
 __u16 bustype;
 __u16 vendor;
 __u16 product;
 __u16 version;
};
 
EV=f
 


后记:
后来的工作中,Sam又看到Hi3716C中,如何使用Driver将红外遥控器模拟成一个Keyboard.
http://blog.sina.com.cn/s/blog_602f877001019wtx.html


其实原理非常类似．　都需要指出支持什么Type的Event.
注3：不同类型的Input Event：
#define EV_SYN          0x00    表示设备支持所有的事件
#define EV_KEY          0x01    键盘或者按键，表示一个键码  
#define EV_REL          0x02    鼠标设备，表示一个相对的光标位置结果
#define EV_ABS          0x03    手写板产生的值，其是一个绝对整数值 
#define EV_MSC          0x04    其他类型 
#define EV_LED          0x11    LED灯设备
#define EV_SND          0x12    蜂鸣器，输入声音 
#define EV_REP          0x14    允许重复按键类型 
#define EV_PWR          0x16    电源管理事件 
#define EV_FF_STATUS 0x17
#define EV_MAX 0x1f
#define EV_CNT (EV_MAX+1)


也要指出每种Type的Event中又分别支持什么具体值.
然后才是创建Device.