2.6内核输入子系统分析-续

上文介绍了input_dev、input_handle、input_handler三者是如何联系起来了，现在继续介绍如何通过它们来传递信息。

在开始之前还是先引用一位大侠的帖子：

引：

现在看用户获取触摸屏输入的一个流程(以tsdev为例/drivers/input/tsdev.c)：
static struct file_operations tsdev_fops = {
         .owner =         THIS_MODULE,
         .open =          tsdev_open,
         .release =       tsdev_release,
         .read =          tsdev_read,
         .poll =          tsdev_poll,
         .fasync =        tsdev_fasync,
         .ioctl =         tsdev_ioctl,
};
假设所有初始化早已完成，用户open该设备后，使用read系统调用进入内核，系统
转移控制到tsdev_read，使用wait_event_interruptible等待事件。

此时驱动层得到用户输入，于是调用input_report_abs，input_report_abs只是
input_event的简单包装：
static inline void input_report_abs(struct input_dev *dev, 
                                      unsigned int code, int value)
{
         input_event(dev, EV_ABS, code, value);
}

void input_event(struct input_dev *dev, unsigned int type, 
                                   unsigned int code, int value)
{
     ...
     switch (type) {
         ...
         case EV_ABS:
             ...
             break;
         ...
     }
     ...

     if (dev->grab)
         dev->grab->handler->event(dev->grab, type, code, value);
     else
         list_for_each_entry(handle, &dev->h_list, d_node)
             if (handle->open)
                 handle->handler->event(handle, type, code, value);
}
前面的处理关系具体设备，见最后对handler函数的调用，就是从input_dev的h_list链
上的input_handle获得每一个相关input_handler，并调用其中的event函数，对tsdev
来说：
static struct input_handler tsdev_handler = {
         .event =         tsdev_event,
         .connect =       tsdev_connect,
         .disconnect =    tsdev_disconnect,
         .fops =          &tsdev_fops,
         .minor =         TSDEV_MINOR_BASE,
         .name =          "tsdev",
         .id_table =      tsdev_ids,
};
即调用tsdev_event函数，接着看：
static void tsdev_event(struct input_handle *handle, unsigned int type,
                         unsigned int code, int value)
{
     ...
     switch (type) {
         case EV_ABS:
             break;
     ...
     list_for_each_entry(list, &tsdev->list, node) {
         int x, y, tmp;
         do_gettimeofday(&time);
         list->event[list->head].millisecs = time.tv_usec / 100;
         list->event[list->head].pressure = tsdev->pressure;

         x = tsdev->x;
         y = tsdev->y;
         /* Calibration */
         if (!list->raw) {
             x = ((x * tsdev->cal.xscale) >> 8) + tsdev->cal.xtrans;
             y = ((y * tsdev->cal.yscale) >> 8) + tsdev->cal.ytrans;
             if (tsdev->cal.xyswap) {
                 tmp = x; x = y; y = tmp;
             }
         }

         list->event[list->head].x = x;
         list->event[list->head].y = y;
         list->head = (list->head + 1) & (TSDEV_BUFFER_SIZE - 1);
         kill_fasync(&list->fasync, SIGIO, POLL_IN);
     }
     wake_up_interruptible(&tsdev->wait);
}
它填充数据，并唤醒等待着的请求。于是前面等待着的read请求就可继续了，
回到tsdev_read中，copy_to_user拷贝数据，最后返回用户层。


一个简单流程就结束了。

注：
    原文请看以下网址：


看了以上的内容，相信你对2.6内核的输入子系统的消息传递过程应该有个大概的了解了，现在我就如何通过input_dev、input_handle、input_handler这三者传递信息进行详细的分析：
################
从开始
################
static ssize_t tsdev_read(struct file *file, char __user *buffer, size_t count,
                          loff_t * ppos)
{
        struct tsdev_list *list = file->private_data;
        int retval = 0;

    /* 设备存在(exist=1:在tsdev_connect函数里设置)，但缓冲中无数据，而又配置为非阻塞读取方式，直接返回 */
        if (list->head == list->tail && list->tsdev->exist && (file->f_flags & O_NONBLOCK))
                return -EAGAIN;
    /* 否则睡眠等待数据都来临 */
        retval = wait_event_interruptible(list->tsdev->wait,
                        list->head != list->tail || !list->tsdev->exist);
    /* 被信号中断唤醒，直接返回 */
        if (retval)
                return retval;
    /* 检查设备是否还存在，不存在(exist=0:在tsdev_disconnect函数中设置)的话直接返回 */
        if (!list->tsdev->exist)
                return -ENODEV;
    /* 有数据，循环读取用户所需要都数据 */
        while (list->head != list->tail &&
               retval + sizeof (struct ts_event) <= count) {
                if (copy_to_user (buffer + retval, list->event + list->tail,
                                  sizeof (struct ts_event)))
                        return -EFAULT;
                list->tail = (list->tail + 1) & (TSDEV_BUFFER_SIZE - 1);//更新读指针
                retval += sizeof (struct ts_event);//更新读字节数
        }

        return retval;
}

#################

#################
        input_report_abs(&ts.dev, ABS_X, ts.xp);
        input_report_abs(&ts.dev, ABS_Y, ts.yp);

        input_report_key(&ts.dev, BTN_TOUCH, 1);
        input_report_abs(&ts.dev, ABS_PRESSURE, 1);
        input_sync(&ts.dev);

###########################

###########################
static inline void input_report_abs(struct input_dev *dev, unsigned int code, int value)
{
        input_event(dev, EV_ABS, code, value);
}


##########################

##########################
void input_event(struct input_dev *dev, unsigned int type, unsigned int code, int value)
{
struct input_handle *handle;
........................................................................................................
        switch (type) {
                case EV_ABS:

                        if (code > ABS_MAX || !test_bit(code, dev->absbit))//一些条件测试
                                return;

                        if (dev->absfuzz[code]) {
                                if ((value > dev->abs[code] - (dev->absfuzz[code] >> 1)) &&
                                    (value < dev->abs[code] + (dev->absfuzz[code] >> 1)))
                                        return;

                                if ((value > dev->abs[code] - dev->absfuzz[code]) &&
                                    (value < dev->abs[code] + dev->absfuzz[code]))
                                        value = (dev->abs[code] * 3 + value) >> 2;

                                if ((value > dev->abs[code] - (dev->absfuzz[code] << 1)) &&
                                    (value < dev->abs[code] + (dev->absfuzz[code] << 1)))
                                        value = (dev->abs[code] + value) >> 1;
                        }

                        if (dev->abs[code] == value)//比较当前值与上一次都值是否相同，相同则不作处理
                                return;

                        dev->abs[code] = value;//备份当前值，以便下一次作比较
                        break;
...............................................................................................................
        if (type != EV_SYN)
                dev->sync = 0;

        if (dev->grab)
                dev->grab->handler->event(dev->grab, type, code, value);
        else
                list_for_each_entry(handle, &dev->h_list, d_node)//通过input_dev找出与其联系的input_handle
                        if (handle->open)//相应的接口设备(比如tsdev)被打开(通过调用tsdev.c的tsdev_open函数进而调用input_open_device
                        函数增加handle->open的计数值)
                                handle->handler->event(handle, type, code, value);//调用该接口设备的event函数对数据进行处理
}

################
在结束
################
static void tsdev_event(struct input_handle *handle, unsigned int type,
                        unsigned int code, int value)
{
        struct tsdev *tsdev = handle->private;
        struct tsdev_list *list;
        struct timeval time;

        switch (type) {
        case EV_ABS:
                switch (code) {
                case ABS_X:
                        tsdev->x = value;//记录x坐标值
                        break;
                case ABS_Y:
                        tsdev->y = value;//记录y坐标值
                        break;
                case ABS_PRESSURE:
                        if (value > handle->dev->absmax[ABS_PRESSURE])
                                value = handle->dev->absmax[ABS_PRESSURE];
                        value -= handle->dev->absmin[ABS_PRESSURE];
                        if (value < 0)
                                value = 0;
                        tsdev->pressure = value;//记录触摸屏的按压状态
                        break;
                }
                break;
...................................................................................................
        if (type != EV_SYN || code != SYN_REPORT)//键值的传递以EV_SYN为结束标志(通过input_sync函数)，等到数据都填充好tsdev结构后再统一发送出去，否则直接返回，继续填充另一个数据
                return;

        list_for_each_entry(list, &tsdev->list, node) {    //通过tsdev获取struct tsdev_list结构(在tsdev_open函数中定义):
                                //list_add_tail(&list->node, &tsdev_table[i]->list);
                int x, y, tmp;

                do_gettimeofday(&time);            //填充事件的时间
                list->event[list->head].millisecs = time.tv_usec / 100;
                list->event[list->head].pressure = tsdev->pressure;//填充触摸屏的状态

                x = tsdev->x;
                y = tsdev->y;

                /* Calibration */
                if (!list->raw) {
                        x = ((x * tsdev->cal.xscale) >> 8) + tsdev->cal.xtrans;
                        y = ((y * tsdev->cal.yscale) >> 8) + tsdev->cal.ytrans;
                        if (tsdev->cal.xyswap) {
                                tmp = x; x = y; y = tmp;
                        }
                }

                list->event[list->head].x = x;        //填充x坐标值
                list->event[list->head].y = y;        //填充y坐标值
                list->head = (list->head + 1) & (TSDEV_BUFFER_SIZE - 1);//更新写指针
                kill_fasync(&list->fasync, SIGIO, POLL_IN);
        }
        wake_up_interruptible(&tsdev->wait);//唤醒睡眠在tsdev->wait下等待数据都进程读取数据。至此，数据传递过程结束，开始新一轮的数据传递。
}