Open Source Summit North America 2022

The Linux media subsystem provides a comprehensive Video for Linux API framework (V4L version 2 or V4L2 in short) to support video capture devices. For example USB webcams, cameras, streaming from M2M devices as well as display devices. The framework provides utilities and test functions to verify the driver implementations or user applications. This presentation covers video device enumeration and the controls provided by V4L2 framework for camera devices. Below is typical flow of video device enumeration: • The video devices should be defined in device tree according to the features it supports • The user controls specific to the video devices should be implemented • All such controls needs to be well documented This talk explores various V4L2 controls exposed to the user space and their implementation in the kernel space. We will also look into the controls that are applicable to video devices and associated video sub-devices. From user space perspective we will look into how the v4l2-ctl tool can be used to verify conformance of the driver and the user controls provided by the device. At the end of the talk, we hope the audience will have better understanding about V4L2 Controls implementation for Video capture devices.