核心层主要都是在input.c中处理。这里会处理各种Event,各种sensor,触摸事件,按键事件等等。流程图如下,
input_event方法直接调用input_handle_event方法进行处理,
void input_event(struct input_dev *dev, unsigned int type, unsigned int code, int value) { unsigned long flags; //判断是否是注册时的event类型，驱动probe时注册input_dev时设置了能响应的event类型 if (is_event_supported(type, dev->evbit, EV_MAX)) { spin_lock_irqsave(&dev->event_lock, flags); //自旋锁枷锁 input_handle_event(dev, type, code, value); spin_unlock_irqrestore(&dev->event_lock, flags); //解锁 } }input_handle_event首先调用input_get_disposition方法获取发送Event的类型,然后根据类型分别处理。
在上个小节中,发送加速度值的类型时EV_ABS,发送时间的值是EV_SYN。
input_get_disposition方法有关sensor代码如下,
case EV_SYN: switch (code) { case SYN_CONFIG: case SYN_TIME_SEC: case SYN_TIME_NSEC: disposition = INPUT_PASS_TO_ALL; break; ••• case EV_ABS: if (is_event_supported(code, dev->absbit, ABS_MAX)) disposition = input_handle_abs_event(dev, code, &value); break;由此可见,sensor的时间事件返回的是INPUT_PASS_TO_ALL
对于sensor事件, input_handle_abs_event 一般返回INPUT_PASS_TO_HANDLERS。
这些值的定义如下,
#define INPUT_IGNORE_EVENT 0 #define INPUT_PASS_TO_HANDLERS 1 #define INPUT_PASS_TO_DEVICE 2 #define INPUT_SLOT 4 #define INPUT_FLUSH 8 #define INPUT_PASS_TO_ALL (INPUT_PASS_TO_HANDLERS | INPUT_PASS_TO_DEVICE)input_handle_event方法最后会调用input_pass_values方法进行处理,
input_pass_values(dev, dev->vals, dev->num_vals);最后的input_to_handler主要逻辑如下,
if (handler->events) handler->events(handle, vals, count); else if (handler->event) for (v = vals; v != end; v++) handler->event(handle, v->type, v->code, v->value);input_to_handler()调用handler->events()和handler->event()，不同的handler，handler->event()函数不同，
这样input_event()就把事件上报给device或handler处理了，整个inputcore层的工作完成了。具体的处理是
handler做的事情。
evdev是/kernel/drivers/input下众多事件处理器handler其中的一个,其对应的init方法是evdev_init,如下,
static int __init evdev_init(void) { return input_register_handler(&evdev_handler); }初始化就是往input核心中注册一个input_handler类型的evdev_handler，定义如下,
static struct input_handler evdev_handler = { .event = evdev_event, .events = evdev_events, .connect = evdev_connect, .disconnect = evdev_disconnect, .legacy_minors = true, .minor = EVDEV_MINOR_BASE, .name = "evdev", .id_table = evdev_ids, };基本是一个input和evdev方法的对应关系。整个调用流程图如下,
input.c的input_register_handler方法如下,
int input_register_handler(struct input_handler *handler) { struct input_dev *dev; int error; error = mutex_lock_interruptible(&input_mutex); if (error) return error; INIT_LIST_HEAD(&handler->h_list); list_add_tail(&handler->node, &input_handler_list); //添加进handler 链表 //遍历input_dev这个链表，依次调用下面的input_attach_handler去匹配input_dev list_for_each_entry(dev, &input_dev_list, node) input_attach_handler(dev, handler); input_wakeup_procfs_readers(); mutex_unlock(&input_mutex); return 0; } EXPORT_SYMBOL(input_register_handler);最后input_attach_handler会回调evdev.c的connect方法, connect指向的函数为evdev_connect，在该方法中,
会初始化evdev结构,
evdev = kzalloc(sizeof(struct evdev), GFP_KERNEL); ••• dev_set_name(&evdev->dev, "event%d", dev_no); evdev->handle.dev = input_get_device(dev); evdev->handle.name = dev_name(&evdev->dev); evdev->handle.handler = handler; evdev->handle.private = evdev; evdev->dev.devt = MKDEV(INPUT_MAJOR, minor); evdev->dev.class = &input_class; evdev->dev.parent = &dev->dev; evdev->dev.release = evdev_free; device_initialize(&evdev->dev);初始化完成之后,将handle 注册到input核心中去
error = input_register_handle(&evdev->handle);最后将device 添加到/sys/class/input/下面，所以可以看到/dev/input下面看到：event0等 字样字符设备文件，
error = device_add(&evdev->dev);evdev结构体如下,
struct evdev { int open; //打开标志 struct input_handle handle; //包含的handle结构 wait_queue_head_t wait; struct evdev_client __rcu *grab;// evdev_client结构 //evdev_client 链表，这说明一个evdev设备可以处理多个evdev_client，可以有多个进程访问evdev设备 struct list_head client_list; spinlock_t client_lock; /* protects client_list */ struct mutex mutex; struct device dev; struct cdev cdev; bool exist; };evdev_client结构体如下,
struct evdev_client { unsigned int head; //buffer数组的索引头 unsigned int tail; //buffer数组的索引尾 unsigned int packet_head; /* [future] position of the first element of next packet */ spinlock_t buffer_lock; /* protects access to buffer, head and tail */ struct wake_lock wake_lock; bool use_wake_lock; char name[28]; struct fasync_struct *fasync; //异步通知函数 struct evdev *evdev; struct list_head node; //链表 int clkid; unsigned int bufsize; //input_event数据结构的数组，input_event代表一个事件，基本成员：类型（type），编码（code），值（value） struct input_event buffer[]; };evdev.c 方法中的对应关系如下,
static struct input_handler evdev_handler = { .event = evdev_event, .events = evdev_events, .connect = evdev_connect, .disconnect = evdev_disconnect, .legacy_minors = true, .minor = EVDEV_MINOR_BASE, .name = "evdev", .id_table = evdev_ids, };event对应的evdev_event方法最后还是会调用evdev_events方法进行处理, evdev_events方法的处理流程图如下,
每当input device上报一个事件时,会将其交给和它匹配的handler的event函数处理.在evdev中这个event函数。
__pass_event 方法如下,
static void __pass_event(struct evdev_client *client, const struct input_event *event) { client->buffer[client->head++] = *event; 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 (client->use_wake_lock) wake_unlock(&client->wake_lock); } if (event->type == EV_SYN && event->code == SYN_REPORT) { client->packet_head = client->head; if (client->use_wake_lock) wake_lock(&client->wake_lock); kill_fasync(&client->fasync, SIGIO, POLL_IN); } }这里的操作很简单.就是将event(上传数据)保存到client->buffer中.而client->head就是当前的数据位置.注意这里
是一个环形缓存区.写数据是从client->head写.而读数据则是从client->tail中读.
和Framework进行交互一般都是evdev.c,对应的方法如下,
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, ••• };例如,上层调用read 方法读取对应sysfs文件节点的数据时,调用的是evdev_read方法,
static ssize_t evdev_read(struct file *file, char __user *buffer, size_t count, loff_t *ppos) { //这个客户端结构在打开的时候分配并保存在file->private_data中 struct evdev_client *client = file->private_data; struct evdev *evdev = client->evdev; struct input_event event; size_t read = 0; int error; if (count != 0 && count < input_event_size()) return -EINVAL; for (;;) { if (!evdev->exist) return -ENODEV; if (client->packet_head == client->tail && (file->f_flags & O_NONBLOCK)) return -EAGAIN; /* * count == 0 is special - no IO is done but we check * for error conditions (see above). */ if (count == 0) break; while (read + input_event_size() <= count && evdev_fetch_next_event(client, &event)) { //将事件复制到用户空间 if (input_event_to_user(buffer + read, &event)) return -EFAULT; read += input_event_size(); } if (read) break; if (!(file->f_flags & O_NONBLOCK)) { //如果设置了非阻塞操作，则会立刻返回 error = wait_event_interruptible(evdev->wait, client->packet_head != client->tail || !evdev->exist); if (error) return error; } } return read; }和上面__pass_event方法刚好相反。这样,通过read方法,就可以将数据从内核态复制到用户态。
