How hid-generic driver catch the event from the mouse device

I have some questions regarding the hid-generic and implementing my own driver. Below is the hid-generic source code. hid-generic.c source code My questions are: 1. How does the hid-generic driver report the behavior from the mouse to the kernel? > The source code is too simple. I cannot find which part provides this transformation. 2. What is the actual purpose of the raw_event function within the driver code? Is it necessary to have when implementing the device driver? 3. What would you recommend to set up a test environment for the HID device in order to make sure it functions correctly on a Raspberry Pi? Any tools used for testing in the industrial environment for the HID device driver?