Input subsystem of Linux driver subsystem (5)

Input subsystem of Linux driver subsystem (5)

5. Summary

5.1 Event Reporting Process Analysis

L General reporting process: Device Driver layer-> core layer-> event processing layer-> Application Layer

L specific called functions (taking evdev as an example): input_event ()-> input_handle_event ()-> input_pass_event ()-> handle-> Handler-> event (handle, type, code, value)-> evdev_event ()-> evdev_pass_event (), and then assign the value to the client (struct evdev_client) through client-> buffer [client-> head ++] = * event)

It is strange that this is not still in the kernel space and is not passed to the application space at all. Don't forget that the event driver layer also implements a file_operations. Let's take a look at the evdev_read function:

Static ssize_t evdev_read (struct file * file, char _ User * buffer,

Size_t count, loff_t * PPOs)

{

Struct evdev_client * client = file-> private_data;

Struct evdev * evdev = client-> evdev;

Struct input_eventevent;

 

While (retval + input_event_size () <= count &&

Evdev_fetch_next_event (client, & event )){

 

If (input_event_to_user (buffer + retval, & event ))

Return-efault;

 

Retval + = input_event_size ();

}

}

You can see it. Use input_event_to_user ()-> copy_to_user () to transfer the information to the user space.

 

5.2 relationship between input_dev, input_handler, and input_handle

L relationship between input_dev, input_handler, and input_handle: