This page is about kernel development, specifically targeted at device drivers and real-time video and audio development, such as hacking and improving drivers for webcams, developing jack and syphon-like (video jack) functionality.
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The two major books on linux driver development are fairly outdated and contain little information on video development. Therefore the main up-to-date resources you will find are online.
General series on linux drivers: http://www.linuxforu.com/tag/linux-device-drivers-series
Be sure to familiarize yourself with ioctl's.
Write and Submit your first Kernel Patch
- Documentation/HOWTO has very good material 
- The book Linux Kernel in a Nutshell is free and describes compiling the kernel etc.
- Coding style: 8 space-tabs, K&R style
- Scripts subdir: scripts to show maintainers, test style of a file, etc.
Video driver development resources
v4l2 is the current API.