Input之我见01——设备驱动初探

struct input_id {
 __u16 bustype;
 __u16 vendor;
 __u16 product;
 __u16 version;
};

input_event用于存储每一次传输的数据，这是个固定大小的结构体。

struct input_event {
 struct timeval time;
 __u16 type;
 __u16 code;
 __s32 value;
};

其中type定义 在Kernel（3.14）的Input子系统中，定义如下18种Input事件，常用的也就是前面5，6种

/* Events */

#define EV_SYN 0x00 //用于同步
#define EV_KEY 0x01 //用于按键，遥控器等，键值的输入设备
#define EV_REL 0x02 //相对事件，用于鼠标的输入
#define EV_ABS 0x03 //绝对事件，用于触摸屏
#define EV_MSC 0x04
#define EV_LED 0x11
#define EV_SND 0x12
#define EV_REP 0x14
#define EV_FF 0x15
#define EV_PWR 0x16
#define EV_FF_STATUS 0x17
#define EV_MAX 0x1f

EventHub.h
/*
* Input device classes.
*/
enum {
 /* The input device is a keyboard or has buttons. */
INPUT_DEVICE_CLASS_KEYBOARD= 0x00000001,

 /* The input device is an alpha-numeric keyboard (not just a dial pad). */
INPUT_DEVICE_CLASS_ALPHAKEY= 0x00000002,

 /* The input device is a touchscreen or a touchpad (either single-touch or multi-touch). */
INPUT_DEVICE_CLASS_TOUCH= 0x00000004,

...
};
 

struct input_handler{
 void *private;
 void (*event)(struct input_handle*handle, unsigned int type, unsigned int code, int value);
 bool (*filter)(struct input_handle*handle, unsigned int type, unsigned int code, int value);
 bool (*match)(struct input_handler*handler, struct input_dev*dev);
 int (*connect)(struct input_handler*handler, struct input_dev*dev, const struct input_device_id*id);
 void (*disconnect)(struct input_handle*handle);
 void (*start)(struct input_handle*handle);
......
 struct list_head h_list;
 struct list_head node;
};

input_handle：input设备的句柄

struct input_handle {

 void *private;

 int open;
 const char *name;

 struct input_dev *dev;
 struct input_handler *handler;

 struct list_head d_node;
 struct list_head h_node;
};

input_dev：input设备

struct input_dev {
 const char *name;
 const char *phys;
 const char *uniq;
 struct input_id id;

 unsigned long evbit[BITS_TO_LONGS(EV_CNT)];
 unsigned long keybit[BITS_TO_LONGS(KEY_CNT)];
 unsigned long relbit[BITS_TO_LONGS(REL_CNT)];
....
 int (*setkeycode)(struct input_dev *dev,
 const struct input_keymap_entry *ke,
 unsigned int *old_keycode);
 int (*getkeycode)(struct input_dev *dev,
 struct input_keymap_entry *ke);

...

 unsigned long key[BITS_TO_LONGS(KEY_CNT)];
 unsigned long led[BITS_TO_LONGS(LED_CNT)];
 unsigned long snd[BITS_TO_LONGS(SND_CNT)];
 unsigned long sw[BITS_TO_LONGS(SW_CNT)];

 int (*open)(struct input_dev *dev);
 void (*close)(struct input_dev *dev);
 int (*flush)(struct input_dev *dev, struct file *file);
 int (*event)(struct input_dev *dev, unsigned int type, unsigned int code, int value);

 struct input_handle __rcu *grab;
...
 struct device dev;

 struct list_head h_list;
 struct list_head node;
};

这三者 Input_dev，hander，与Hande的关系

input_register_device(remote->input);

=》

int input_register_device(struct input_dev *dev)
{
...
//添加到全局设备
error = device_add(&dev->dev);
...
//添加到设备链表
list_add_tail(&dev->node, &input_dev_list);
//遍历input_handler_list链表，以node为关键字，把dev加入到handler_list中
list_for_each_entry(handler, &input_handler_list, node)
 input_attach_handler(dev, handler);

在input_attach_handler中，

static int input_attach_handler(struct input_dev *dev, struct input_handler *handler)
{

 id = input_match_device(handler, dev);
 if (!id)
 return -ENODEV;
...
 error = handler->connect(handler, dev, id);
...
 return error;
}

通过id进行匹配，第一次的话hander链表中没有dev对应的handler，就进行connect，其实是调用input_register_handle()。把input_dev，input_handler，input_handle关联起来。

input_event(dev,EV_KEY,scancode,type);
input_sync(dev);

主要看input_event

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;

 event.type = type;
 event.code = code;
 event.value = value;
...
 client = rcu_dereference(evdev->grab);
 if (client)
 evdev_pass_event(client, &event);
 else
 list_for_each_entry_rcu(client, &evdev->client_list, node)
 evdev_pass_event(client, &event);

...
 if (type == EV_SYN && code == SYN_REPORT)
 wake_up_interruptible(&evdev->wait);
}

把事件通过evdev_pass_event传递给client，如果是同步事件的话，就调用wait，唤醒相应的监听进行。