Embedded Linux Conference + Android Builders Summit

Media devices can be very complex to support in software - for example, a small USB TV stick is packed with several components providing the functionality to tune, stream analog and/or digital video and audio. Some hybrid devices support both analog, and digital TV tuning
capability with or without a remote control capability. A single TV device, which connects to the PC on a USB bus, could have one or more I2C buses internally to implement tuning and remote control features. Media devices appear to the kernel as a group of independent devices. Each device implements a function which could be shared by one or more functions. As a result these devices depend on each other to provide a complete media service. For instance, Tuner is shared by analog and digital TV functions.

Linux Media drivers that drive one single media TV stick are a diversified group. Drivers that provide Analog and digital TV functions have to coordinate access to their shared functions. Further more, some devices provide multiple almost-independent functions. USB and PCI core work to allow multiple drivers to handle those almost-independent functions. For instance, snd-usb-audio driver will handle USB Audio Class devices, including some em28x devices, as it provides an independent UAC interface, while analog and digital TV are provided via another interface.

This talk will go over the existing media driver sharing constructs, their deficiencies, and discuss what is being done to solve the sharing problems across media drivers as well as cases when non-media drivers such as the snd-usb-audio driver is in the mix.