linux驱动——input输入子系统（1）—输入子系统核心层（Input Core）

h101com

　　1、
　　

　　上图是input输入子系统框架，输入子系统由输入子系统核心层（ Input Core ），驱动层和事件处理层（EventHandler）三部份组成。一个输入事件，如鼠标移动，键盘按键按下，joystick的移动等等通过 inputdriver -> Input core ->Event handler -> userspace 到达用户空间传给应用程序。


　　subsys_initcall(input_init);
module_exit(input_exit);

static int __init input_init(void)
{
int err;

err = class_register(&input_class);//注册一个名为input的类
　　其中有：

• struct class input_class = {
  
  
• .name = "input",
  
  
• };
  
  
• if (err) {
  
  
• printk(KERN_ERR "input: unable to register input_dev class\n");
  
  
• return err;
  
  
• }
  
  
• 
  
  
• err = input_proc_init();
  
  
• if (err)
  
  
• goto fail1;
  

　　err = register_chrdev(INPUT_MAJOR, "input", &input_fops);注册了主设备号为INPUT_MAJOR的字符设备，操作函数集是：input_fops，如下所示：

• static const struct file_operations input_fops = {
  
  
• .owner = THIS_MODULE,
  
  
• .open = input_open_file,
  
  
• };
  
  
• if (err) {
  
  
• printk(KERN_ERR "input: unable to register char major %d", INPUT_MAJOR);
  
  
• goto fail2;
  
  
• }
  
  
• 
  
  
• return 0;
  
  
• 
  
  
• 
  
  
• fail2: input_proc_exit();
  
  
• fail1: class_unregister(&input_class);
  
  
• return err;
  
  
• }
  
  
• static void __exit input_exit(void)  //做和input_init函数做相反的工作
  
  
• {
  
  
• input_proc_exit();
  
  
• unregister_chrdev(INPUT_MAJOR, "input");
  
  
• class_unregister(&input_class);
  
  
• }
  

　　2.1、接着看下input_open_file函数，源码如下：

• static int input_open_file(struct inode *inode, struct file *file)
  
  
• {
  
  
• struct input_handler *handler;
  
  
• const struct file_operations *old_fops, *new_fops = NULL;
  
  
• int err;
  
  
• 
  
  
• lock_kernel();
  
  
• /* No load-on-demand here? */
  
  
• handler = input_table[iminor(inode) >> 5];
  

　　其中iminor(inode)为打开文件所对应的次设备号。input_table是一个structinput_handler全局数组，只有8个元素，其定义为：
static struct input_handler *input_table[8];
　　首先将设备结点的次设备号右移5位做为索引值到input_table中取对应项，从这里也可以看到，一个handler代表32（1> 5] = handler，其将handler赋给了input_table数组，所使用的规则也是右移5位。

　　/**
* struct input_handler - implements one of interfaces for input devices
* @private: driver-specific data
* @event: event handler. This method is being called by input core with
* interrupts disabled and dev->event_lock spinlock held and so
* it may not sleep
* @connect: called when attaching a handler to an input device
* @disconnect: disconnects a handler from input device
* @start: starts handler for given handle. This function is called by
* input core right after connect() method and also when a process
* that "grabbed" a device releases it
* @fops: file operations this driver implements
* @minor: beginning of range of 32 minors for devices this driver
* can provide
* @name: name of the handler, to be shown in /proc/bus/input/handlers
* @id_table: pointer to a table of input_device_ids this driver can
* handle
* @blacklist: pointer to a table of input_device_ids this driver should
* ignore even if they match @id_table
* @h_list: list of input handles associated with the handler
* @node: for placing the driver onto input_handler_list
*
* Input handlers attach to input devices and create input handles. There
* are likely several handlers attached to any given input device at the
* same time. All of them will get their copy of input event generated by
* the device.
*
* Note that input core serializes calls to connect() and disconnect()
* methods.
*/
struct input_handler {


void *private;


void (*event)(struct input_handle *handle, unsigned int type, unsigned int code, int value);
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);


const struct file_operations *fops;
int minor;
const char *name;


const struct input_device_id *id_table;
const struct input_device_id *blacklist;


struct list_head h_list;
struct list_head node;
};


if (!handler || !(new_fops = fops_get(handler->fops))) {
//检查handler是否存在
err = -ENODEV;
goto out;
}


/*
* That's _really_ odd. Usually NULL ->open means "nothing special",
* not "no device". Oh, well...
*/
if (!new_fops->open) {  //判断new_fops->open是否存在
fops_put(new_fops);
err = -ENODEV;
goto out;
}
old_fops = file->f_op;
file->f_op = new_fops;


err = new_fops->open(inode, file);  //使用新的open函数重新打开设备


if (err) {
fops_put(file->f_op);
file->f_op = fops_get(old_fops);
}
fops_put(old_fops);
out:
unlock_kernel();
return err;
}