input子系统一 主要数据结构

一、input子系统的分层结构

linux系统实现了很多子系统架构，每个子系统都是分层的；input子系统也不例外，主要分为三层：

(1) 硬件驱动层：与硬件相关，是驱动开发的部分。

(2) 系统核心层：是连接其他两层的纽带，对应的代码为drivers/input/input.c、input-mt.c等。

(3) 事件处理层：真正的事件处理部分，为应用程序提供读写接口；对应的代码为drivers/input/evdev.c、mousedev.c等。

二、主要数据结构

struct input_value {
	__u16 type;
	__u16 code;
	__s32 value;
};

input设备report数据最终调用的函数是void input_event(struct input_dev *dev, unsigned int type, unsigned int code, int value)；这个函数的参数最终会填到上述结构中。

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

	unsigned long propbit[BITS_TO_LONGS(INPUT_PROP_CNT)];

	unsigned long evbit[BITS_TO_LONGS(EV_CNT)];
	unsigned long keybit[BITS_TO_LONGS(KEY_CNT)];
	unsigned long relbit[BITS_TO_LONGS(REL_CNT)];
	unsigned long absbit[BITS_TO_LONGS(ABS_CNT)];
	unsigned long mscbit[BITS_TO_LONGS(MSC_CNT)];
	unsigned long ledbit[BITS_TO_LONGS(LED_CNT)];
	unsigned long sndbit[BITS_TO_LONGS(SND_CNT)];
	unsigned long ffbit[BITS_TO_LONGS(FF_CNT)];
	unsigned long swbit[BITS_TO_LONGS(SW_CNT)];

	unsigned int hint_events_per_packet;

	unsigned int keycodemax;
	unsigned int keycodesize;
	void *keycode;

	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);

	struct ff_device *ff;

	unsigned int repeat_key;
	struct timer_list timer;

	int rep[REP_CNT];

	struct input_mt *mt;

	struct input_absinfo *absinfo;

	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;

	spinlock_t event_lock;
	struct mutex mutex;

	unsigned int users;
	bool going_away;

	struct device dev;

	struct list_head	h_list;
	struct list_head	node;

	unsigned int num_vals;
	unsigned int max_vals;
	struct input_value *vals;

	bool devres_managed;
};

input_dev代表一个输入设备，每个输入设备的驱动文件中都能找到它，h_list用于挂handle，node用于挂自己到全局的list上。

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

struct input_handler {

	void *private;

	void (*event)(struct input_handle *handle, unsigned int type, unsigned int code, int value);
	void (*events)(struct input_handle *handle,
		       const struct input_value *vals, unsigned int count);
	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);

	bool legacy_minors;
	int minor;
	const char *name;

	const struct input_device_id *id_table;

	struct list_head	h_list;
	struct list_head	node;
};

input_handler是一个事件处理，包含各种事件处理方法。h_list用于挂handle，node用于挂自己到全局的list上。

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_handle是连接handler和dev的纽带。d_node用于挂dev，h_node用于挂handler。

在dev和handler匹配成功时，connect的时候会创建evdev->handle结构，handle会分别挂在已经匹配的dev和handler结构中。

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

struct evdev {
	int open;
	struct input_handle handle;
	wait_queue_head_t wait;
	struct evdev_client __rcu *grab;
	struct list_head client_list;
	spinlock_t client_lock; /* protects client_list */
	struct mutex mutex;
	struct device dev;
	struct cdev cdev;
	bool exist;
};

struct evdev_client {
	unsigned int head;
	unsigned int tail;
	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;
	struct evdev *evdev;
	struct list_head node;
	int clkid;
	unsigned int bufsize;
	struct input_event buffer[];
};