Research And Development Of User Space Driver For USB Video Device Under Linux

Linux device drivers usually run in kernel space. Recent years, in order to improve the driver development efficiency, some researchers propose the user space driver development concept. Compare to kernel space driver, user-space driver has the following advantages: 1, convenience of debugging; 2, the user space driver error will not cause system crashes; 3, the user space drivers can use the C language library, simplify driver development; 4, user-space drivers are less dependent on the kernel, so have better portability, and can release closed source drivers.The application uses the system calls to communicate with kernel driver, while in user space driver, there needs an appropriate framework to facilitate the interaction between application and driver. In this paper, considering the characteristics of video equipment, it designs and implements the user space V4L2 interaction framework. Using this framework, the application can communicate with user-space drivers under V4L2 standard easily, and also reduces the workload of the user space driver development.Video device has complex working mechanisms and data formats, develop its driver in user space and improve the develop efficiency and reduce debugging difficulty. This article uses Libusb library to design and implement a user space USB video device driver, and uses the C + +, with object-oriented idea to the organize driver development, and realizes a reused transmission buffer module. C++'s more safety in language can increase the driver stability.