Android中Input型输入设备驱动原理分析<二>

来源：互联网发布：网络用语wtf什么意思编辑：程序博客网时间：2024/04/29 16:03

驱动层只是把输入设备注册到输入子系统中,驱动层的代码本身是没有创建设备节点的,而是由EventHander层调用InputCore中的函数来实现,当某个事件触发时都将通过input _event()来将input event传送到input.c中,再由input.c分配事件到每一个"input handler"

2)input _event()是怎么实现的

void input_event(struct input_dev *dev,unsigned int type, unsigned int code, int value)
{
   unsigned long flags;
   if (is_event_supported(type, dev->evbit, EV_MAX)) {
       spin_lock_irqsave(&dev->event_lock, flags);
       add_input_randomness(type, code, value);
       input_handle_event(dev, type, code, value);
       spin_unlock_irqrestore(&dev->event_lock, flags);
   }
}

static void input_handle_event(struct input_dev *dev,unsigned int type, unsigned int code, int value)
{
   int disposition = INPUT_IGNORE_EVENT;
   switch (type) {
   case EV_SYN:
       switch (code) {
       case SYN_CONFIG:
           disposition = INPUT_PASS_TO_ALL;
           break;
       case SYN_REPORT:
           if (!dev->sync) {
               dev->sync = true;
               disposition = INPUT_PASS_TO_HANDLERS;
           }
           break;
       case SYN_MT_REPORT:
           dev->sync = false;
           disposition = INPUT_PASS_TO_HANDLERS;
           break;
       }
       break;
   case EV_KEY:
       if (is_event_supported(code, dev->keybit, KEY_MAX) &&
            !!test_bit(code, dev->key) != value) {
           if (value != 2) {
               __change_bit(code, dev->key);
               if (value)
                   input_start_autorepeat(dev, code);
               else
                   input_stop_autorepeat(dev);
           }
           disposition = INPUT_PASS_TO_HANDLERS;
       }
       break;
   case EV_SW:
       if (is_event_supported(code, dev->swbit, SW_MAX) &&
            !!test_bit(code, dev->sw) != value) {
           __change_bit(code, dev->sw);
           disposition = INPUT_PASS_TO_HANDLERS;
       }
       break;

   case EV_ABS:
       if (is_event_supported(code, dev->absbit, ABS_MAX))
           disposition = input_handle_abs_event(dev, code, &value);
       break;
   case EV_REL:
       if (is_event_supported(code, dev->relbit, REL_MAX) && value)
           disposition = INPUT_PASS_TO_HANDLERS;
       break;
   case EV_MSC:
       if (is_event_supported(code, dev->mscbit, MSC_MAX))
           disposition = INPUT_PASS_TO_ALL;
       break;
   case EV_LED:
       if (is_event_supported(code, dev->ledbit, LED_MAX) &&
            !!test_bit(code, dev->led) != value) {
           __change_bit(code, dev->led);
           disposition = INPUT_PASS_TO_ALL;
       }
       break;
   case EV_SND:
       if (is_event_supported(code, dev->sndbit, SND_MAX)) {
           if (!!test_bit(code, dev->snd) != !!value)
               __change_bit(code, dev->snd);
           disposition = INPUT_PASS_TO_ALL;
       }
       break;
   case EV_REP:
       if (code <= REP_MAX && value >= 0 && dev->rep[code] != value) {
           dev->rep[code] = value;
           disposition = INPUT_PASS_TO_ALL;
       }
       break;
   case EV_FF:
       if (value >= 0)
           disposition = INPUT_PASS_TO_ALL;
       break;
   case EV_PWR:
       disposition = INPUT_PASS_TO_ALL;
       break;
   }
   if (disposition != INPUT_IGNORE_EVENT && type != EV_SYN)
       dev->sync = false;
   if ((disposition & INPUT_PASS_TO_DEVICE) && dev->event)
       dev->event(dev, type, code, value);
   if (disposition & INPUT_PASS_TO_HANDLERS)
       input_pass_event(dev, type, code, value);
}