AD7879-I2C touchscreen 中事件的处理过程

接着上次AD7879-I2C对事件的处理过程分析
1.设置事件
2.上报事件
先看设置事件部分
	__set_bit(EV_ABS, input_dev->evbit);
	__set_bit(ABS_X, input_dev->absbit);
	__set_bit(ABS_Y, input_dev->absbit);
	__set_bit(ABS_PRESSURE, input_dev->absbit);

	__set_bit(EV_KEY, input_dev->evbit);
 __set_bit(BTN_TOUCH, input_dev->keybit);
	input_set_abs_params(input_dev, ABS_X,
			pdata->x_min ? : 0,
			pdata->x_max ? : MAX_12BIT,
			0, 0);
	input_set_abs_params(input_dev, ABS_Y,
			pdata->y_min ? : 0,
			pdata->y_max ? : MAX_12BIT,
			0, 0);
	input_set_abs_params(input_dev, ABS_PRESSURE,
 pdata->pressure_min, pdata->pressure_max, 0, 0);
上面的代码可以看到主要设置input_dev结构体下面的evbit和absbit两个成员数组。
evbit：这个数组以位掩码的形式，代表这个设备支持事件的类型。
absbit：这个数组以位掩码的形式，代表这个这个事件支持的编码。具体设置这个事件编码可以通过 input_set_abs_params来设置。
Abs这个事件编码可以由下面这个结构体描述
struct input_absinfo {
	__s32 value;
	__s32 minimum;
	__s32 maximum;
	__s32 fuzz;
	__s32 flat;
	__s32 resolution;
};
所以input_set_abs_params主要是完成 input_absinfo的设置
void input_set_abs_params(struct input_dev *dev, unsigned int axis,
			  int min, int max, int fuzz, int flat)
{
	struct input_absinfo *absinfo;
	input_alloc_absinfo(dev);
	if (!dev->absinfo)
		return;
	absinfo = &dev->absinfo[axis];
	absinfo->minimum = min;
	absinfo->maximum = max;
	absinfo->fuzz = fuzz;
	absinfo->flat = flat;
	dev->absbit[BIT_WORD(axis)] |= BIT_MASK(axis);
}
EXPORT_SYMBOL(input_set_abs_params);
接着看上报事件部分
	input_report_key(input_dev, BTN_TOUCH, 1);
	input_report_abs(input_dev, ABS_X, ts->x);
	input_report_abs(input_dev, ABS_Y, ts->y);
	input_report_abs(input_dev, ABS_PRESSURE, ts->Rt);
 input_sync(input_dev);
主要完成了相应事件的上报，最后input_sync主要完成事件的同步上报，
static inline void input_sync(struct input_dev *dev)
{
	input_event(dev, EV_SYN, SYN_REPORT, 0);
}
在input.h中可以看到，真正完成上报的是函数 input_event，这个函数在input.c中
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)) {//判断是否支持此种事件类型及事件类型中的编码类型

		spin_lock_irqsave(&dev->event_lock, flags);
		add_input_randomness(type, code, value);//对系统随机熵池有贡献，因为这也是一个随机过程
		input_handle_event(dev, type, code, value);//事件处理函数
		spin_unlock_irqrestore(&dev->event_lock, flags);
	}
}
EXPORT_SYMBOL(input_event);
事件的处理在 input_handle_event完成的
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);
}
通过对事件类型的判断分别进行相应的处理，互不干扰，首先看这几个东东
#define INPUT_IGNORE_EVENT	0
#define INPUT_PASS_TO_HANDLERS	1
#define INPUT_PASS_TO_DEVICE	2
#define INPUT_PASS_TO_ALL (INPUT_PASS_TO_HANDLERS | INPUT_PASS_TO_DEVICE)
它们是事件传递的方式，系统默认是INPUT_IGNORE_EVENT，忽略这个事件， INPUT_PASS_TO_HANDLERS表示事件传递给处理器， INPUT_PASS_TO_DEVICE表示事件传递给设备。触摸屏是通过input_handle_abs_event函数来设置的
static int input_handle_abs_event(struct input_dev *dev,
				  unsigned int code, int *pval)
{
	bool is_mt_event;
	int *pold;
	if (code == ABS_MT_SLOT) {
		/*
		 * "Stage" the event; we'll flush it later, when we
		 * get actual touch data.
		 */
		if (*pval >= 0 && *pval < dev->mtsize)
			dev->slot = *pval;
		return INPUT_IGNORE_EVENT;
	}
	is_mt_event = code >= ABS_MT_FIRST && code <=  ABS_MT_LAST;
	if (!is_mt_event) {//单点触控
		pold = &dev->absinfo[code].value;
	} else if (dev->mt) {//多点触控
		struct input_mt_slot *mtslot = &dev->mt[dev->slot];
		pold = &mtslot->abs[code - ABS_MT_FIRST];
	} else {
		/*
		 * Bypass filtering for multi-touch events when
		 * not employing slots.
		 */
		pold = NULL;
	}
	if (pold) {
		*pval = input_defuzz_abs_event(*pval, *pold,
						dev->absinfo[code].fuzz);
		if (*pold == *pval)
			return INPUT_IGNORE_EVENT;
		*pold = *pval;
	}
	/* Flush pending "slot" event */
	if (is_mt_event && dev->slot != input_abs_get_val(dev, ABS_MT_SLOT)) {
		input_abs_set_val(dev, ABS_MT_SLOT, dev->slot);
		input_pass_event(dev, EV_ABS, ABS_MT_SLOT, dev->slot);
	}
	return INPUT_PASS_TO_HANDLERS;
}
这里主要看 input_pass_event描述事件是怎么被处理的，还有看返回值INPUT_PASS_TO_HANDLERS
static void input_pass_event(struct input_dev *dev,
			     unsigned int type, unsigned int code, int value)
{
	struct input_handler *handler;
	struct input_handle *handle;
	rcu_read_lock();
	handle = rcu_dereference(dev->grab);
	if (handle)//如果是绑定的handle
		handle->handler->event(handle, type, code, value);//调用绑定的handle->handler->event函数
	else {//如果没有绑定	，则遍历dev的h_list链表，寻找handle，如果handle已经打开，说明有进程读取关联的evdev
		bool filtered = false;
		list_for_each_entry_rcu(handle, &dev->h_list, d_node) {
			if (!handle->open)
				continue;
			handler = handle->handler;
			if (!handler->filter) {
				if (filtered)
					break;
				handler->event(handle, type, code, value);//调用事件处理器的event函数，进行事件处理
			} else if (handler->filter(handle, type, code, value))
				filtered = true;
		}
	}
	rcu_read_unlock();
}
这里看到真正完成事件处理是由evdev中的event来完成的。对于触摸屏来说，对应的事件处理器是evdev，所以到evdev.c中找到evdev_event函数
static void evdev_event(struct input_handle *handle,
			unsigned int type, unsigned int code, int value)
{
	struct evdev *evdev = handle->private;
	struct evdev_client *client;
	struct input_event event;
	/*将传过来的事件，赋值给input_event结构*/
	do_gettimeofday(&event.time);
	event.type = type;
	event.code = code;
	event.value = value;
	rcu_read_lock();
	client = rcu_dereference(evdev->grab);
	if (client)
		evdev_pass_event(client, &event);//如果evdev绑定了client，那么处理这个客户端，触摸屏没有绑定
	else
		list_for_each_entry_rcu(client, &evdev->client_list, node)//遍历client链表，调用evdev_pass_event函数
			evdev_pass_event(client, &event);
	rcu_read_unlock();
	if (type == EV_SYN && code == SYN_REPORT)
		wake_up_interruptible(&evdev->wait);//唤醒等待的进程
}
这个函数主要完成client和event的绑定，然后调用 evdev_pass_event函数
static void evdev_pass_event(struct evdev_client *client,
			     struct input_event *event)
{
	/* Interrupts are disabled, just acquire the lock. */
	spin_lock(&client->buffer_lock);
	client->buffer[client->head++] = *event;//将事件赋值给客户端的input_event数组
	client->head &= client->bufsize - 1;
	if (unlikely(client->head == client->tail)) {
		/*
		 * This effectively "drops" all unconsumed events, leaving
		 * EV_SYN/SYN_DROPPED plus the newest event in the queue.
		 */
		client->tail = (client->head - 2) & (client->bufsize - 1);
		client->buffer[client->tail].time = event->time;
		client->buffer[client->tail].type = EV_SYN;
		client->buffer[client->tail].code = SYN_DROPPED;
		client->buffer[client->tail].value = 0;
		client->packet_head = client->tail;
	}
	if (event->type == EV_SYN && event->code == SYN_REPORT) {
		client->packet_head = client->head;
		kill_fasync(&client->fasync, SIGIO, POLL_IN);
	}
	spin_unlock(&client->buffer_lock);
}
这个函数中最重要的意见事情就是把事件赋值给了client的input_event数组，只需要将这个数组传给用户空间，进程就能收到触摸屏按下的信息了。下面看evdev.c下面提供的操作函数集
static const struct file_operations evdev_fops = {
	.owner		= THIS_MODULE,
	.read		= evdev_read,
	.write		= evdev_write,
	.poll		= evdev_poll,
	.open		= evdev_open,
	.release	= evdev_release,
	.unlocked_ioctl	= evdev_ioctl,
#ifdef CONFIG_COMPAT
	.compat_ioctl	= evdev_ioctl_compat,
#endif
	.fasync		= evdev_fasync,
	.flush		= evdev_flush,
	.llseek		= no_llseek,
};
其中 evdev_read的具体实现如下
static ssize_t evdev_read(struct file *file, char __user *buffer,
			  size_t count, loff_t *ppos)
{
	struct evdev_client *client = file->private_data;//client在打开的时候分配并保存再file->private_data中
	struct evdev *evdev = client->evdev;
	struct input_event event;
	int retval = 0;
	if (count < input_event_size())//每次读取的字节数，不要少于input_event结构的大小
		return -EINVAL;
	if (!(file->f_flags & O_NONBLOCK)) {//如果设置了事件阻塞操作
		retval = wait_event_interruptible(evdev->wait,//没有事件就会睡眠在evdev的等待队列上	，等待条件是有事件来或者evdev不存在了，即设备关闭了
				client->packet_head != client->tail ||
				!evdev->exist);
		if (retval)//说明有事件传来或者设备被关闭了，或者内核发过来终止信号
			return retval;
	}
	if (!evdev->exist)
		return -ENODEV;
	while (retval + input_event_size() <= count &&
	       evdev_fetch_next_event(client, &event)) {//evdev_fetch_next_event遍历client里面的input_event buffer数组
		if (input_event_to_user(buffer + retval, &event))//将事件复制到用户空间
			return -EFAULT;
		retval += input_event_size();
	}
	if (retval == 0 && (file->f_flags & O_NONBLOCK))
		return -EAGAIN;
	return retval;//返回复制的数据字节数
}
当有事件传过来的时候，会调用event函数，对input_event buffer进行赋值，然后会通过evdev提供的操作函数集和用户空间进行交互。