My environment : - Yocto v2.19.0 - USB Webcam logitech HD WEBCAM C525
sorry I don't know where can I revise the code you say in the first 1. Enable the following kernel config.
Device Drivers --> Multimedia support ---> [*] Media USB Adapters [*] USB Video Class (UVC) [*] UVC input events device support (NEW)
Please refer to the chapter 2.3.2 of https://www.yoctoproject.org/docs/1.6.1/kernel-dev/kernel-dev.html