The Development Of USB Graphics Card For Linux Based Multiseat Platform

Since the1990s, Linux system has been developed rapidly. Due to design as the core of the network inherited from UNIX and the modular design of the structure, Linux has a very wide range of application as the popular operation system on PC or server and in the embedded environment. Meanwhile, computer’s hardware has also made a rapid development. But for the domestic consumer, it is hard to make a full use of the hardware resources. Such as in the electronic reading room, users need extremely limited hardware resources. And providing each user with one computer may lead to waste of resources and more cost of power; While for students in the remote areas, they need to learn and use computer. But providing each student with a computer is also a great burden. USB graphics multiseat platform technology based on Linux system can enable a computer to support multiple users independently. Each user equipped with a monitor, keyboard and mouse, can log in with his own account and password to use the computer resources without influence other users only by connecting to the USB device. USB graphics multiseat platform significantly reduces hardware costs, and power consumption. The paper is based on a company’s project about the development of USB graphics card for Linux based multiseat platform. The project is mainly included the following contents: Determination of the overall implementation of USB device multiseat platform; Selection of the suitable hardware of the graphics chip and the USB chip; Design of the USB graphics device driver of Xorg module and kernel module based on Linux system; Building multiseat platform to install the driver for software debugging; Trial production and so on.Specifically, the paper focus on the following aspects: First, to list the project requirements according to the product definition book, to determine the hardware and driver design solution based on the existing platform so as to achieve all functional requirements and the most cost-effective design, and then to confirm the graphics chip and USB chip according to the datasheet. Second, based on the analysis of the Linux system and the X Window System release version, to design the USB graphics Xorg driver which agrees with X Window System protocol and the X Window System regulatory requirements, and to verify the validity of Xorg driver on USB graphics multiseat platform; To analysis the architecture and implementation principles of Framebuffer and principles of USB driver in Linux system. Through the Framebuffer driver interface, user-mode process X Server can regard Framebuffer as an image of hardware memory. After be mapped into the process address space, X Server can do the operation on Framebuffer which is equivalent to completion of the operation on the graphics hardware, just like the process transformed into kernel mode. Finally, to compile, install and debug the USB graphics driver based on the Linux system. By setting breakpoints and following the function, to verify the communication between the USB card user platform and Linux hosts.The paper is based on the Linux system and develops the Xorg driver module and the kernel driver module for USB graphics device. It can support the multiseat platform stable and reliable. For the function of the drive module, user-mode process X Server can be transformed for the operation of Framebuffer by the Xorg driver module, just like the process transformed into kernel mode. The kernel driver can do the operation to the hardware directly. Finally, the paper introduces the process and debugging method in GDB environment. At present, the project is being on mass production stage.