| According to the State Council promulgated the "national long-term science and technology development plan(2006-2020)" in 2006, "Core High Base" is one of the 16 major science and technology projects. “Core High Base” is the core of electronic devices, high-end general chips and basic software products for short, the operating system is an important part of the basic software products. The desktop operating system based on Linux plays an important role in data security sensitive department. Connecting external VGA monitor is one of the basic functions of the operating system for laptop. In desktop operating system adaptation development, due to the video card driver(a closed source driver) is not perfect, system and hardware(VIA platform) existing compatibility problems, the VGA display mode(extended mode, copy mode, only the laptop mode, only VGA mode) does not automatically restore after hotplug, and the external screen may has a black area.This papper makes a research of the principle and supplement of VGA device hotpluging mechanism from the following aspects. First, the analysis of VGA hotplug support mechanism of kernel, through the analysis of the kernel related equipment and interrupt handling mechanism, including the interface and interface implementation principle of applications running on user mode provided by kernel. Second, the analysis of VGA hotplug support mechanism of system level user mode applications, such as initrd, DBUS, ACPI, udev, X and colord, including the related information transfer and preservation methods of VGA display. Third, analyze the application level user mode application of VGA display mode control mechanism, through the analysis of gnome-settings-daemon, cinnamon-controlcenter, cinnamon and Xrandr which is related of VGA display control method.With some experiments, I analyse the VGA hotplug mechanism provided by kernel and two method of controlling VGA display mode supported by desktop applications. I find a solution of making the two method of controlling communicate with each other and a solution to restore VGA display mode automatically and display normally after rebooting, hotpluging, resuming from suspend and closing the lid.The solutions above has been tested and applied in 32 bit and 64 bit laptop adaption project, and it proves that the solution is feasible. |
PDF Full Text Request