(2.4.27 is the first 2.4 kernel to bundle RNDIS support, and some other framework improvements.) At this writing, other than architecture- or board-specific setup, and the header files, all the gadget code is in the drivers/usb/gadget directory. The 'gadget' framework is available in 2.6 kernels, as well as 2.4.23 and later. Kernel trees that support specific System-on-Chip platforms often include a driver for that platform’s USB Peripheral Controller. The website includes pointers to a number of these a USB network link can be extremely useful. There may be other public trees with controller or gadget drivers too. The BitKeeper trees are no longer current, but the 'mm' patchsets or various other GIT trees may well have more current code than the current mainstream kernel. The API and several supporting drivers are included in current 2.4 and 2.6 Linux kernels, available through as tarballs, or from vendors supporting customized Linux distributions. Otherwise, a Net2280 PCI card lets you work on a standard PC, developing or debugging gadget drivers on computers you may already own. If you’re comfortable working with embedded Linux platforms, many ARM systems already have Linux support for their integrated USB controllers. Many developers have asked about easy ways to start working with this API. Tests are available too, which can speed hardware bringup substantially. It a good base for integrating and re-using this type of driver code. It’s designed for flexibility: the API handles simple devices, composite (multi-function) ones, multiple configurations, class (or vendor) specific functionality, and more. This is the first such 'USB Gadget' framework on GNU/Linux to support high speed (USB 2.0) devices and arbitrary numbers of endpoints, sharing core models and data structures with the 'host side' USB API. Sometimes it will be the only option there are Linux devices that rely on USB even for their power supplies. Smart gadgets like PDAs, printers, cell phones, cash registers, and network routers often rely on this type of 'Device Controller' USB link as one of their basic connectivity options. But when you’re putting together embedded Linux systems, a USB peripheral controller option is routine it’s often integrated into processors. Many Linux systems will not be able to use it, since they only have PC-style USB Host (master) hardware in a PC, workstation, or server. The drivers implementing and using that API combine to make a useful driver framework for Linux systems that implement USB peripherals. The API makes it easy for peripherals and other devices embedding GNU/Linux system software to act in the USB 'device' (slave) role.

Gadget serial 2.4