This is just a basic linux device driver. This will explain about the poll linux example device driver.

Please refer this URL for the complete tutorial of this source code.

Poll - https://embetronicx.com/tutorials/linux/device-drivers/poll-linux-example-device-driver/

Select - https://embetronicx.com/tutorials/linux/device-drivers/select-linux-example-device-driver/

e-Poll - https://embetronicx.com/tutorials/linux/device-drivers/epoll-in-linux-device-driver/