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The correct ep0 maxpacket size is also reported, as defined by the underlying controller driver. Drivers must make sure the endpoint descriptors match any hardware constraints. This function chooses the right descriptors for a given endpoint according to gadget speed and saves it in the endpoint desc field. Except for the driver data, all fields in this structure are read-only to the gadget driver.
Controller Drivers Drivers for several different usb device chips are gadgetts.
The API standardizes a platform-neutral boundary between two software layers, but the software stack usually has several higher layers. Therefore both entries become the same id assign. There are significant hardware features, such as device-to-device DMA without temporary storage in a memory buffer that would be added using hardware-specific APIs. If no more functions are delaying their activation, the gadget driver will respond to host enumeration procedures.
Other operating systems use other names for this component, such as a "USB Client driver". Slightly more complex gadgets may have more than one single-function configuration at a given speed; or have configurations that only gsdgetfs at one speed. Some hardware also constrains other descriptors. For example, building configuration descriptors from vectors of descriptors for the configurations interfaces and endpoints is now automated, and many drivers now use autoconfiguration to choose hardware endpoints and initialize their descriptors.
USB Gadget API for Linux — The Linux Kernel documentation
Support for other kinds of gadget is expected to be developed and contributed over time, as this driver framework evolves. That liux involve alternate settings or configurations, unless the hardware prevents such operation.
CDC WMC devices are an example where functions often depend on other functions, with some functions subsidiary to others. Description This copies descriptors into the response buffer, building a descriptor for that configuration.
HNP support should be reported through a user interface two LEDs could sufficeand is triggered in some cases when the host suspends the peripheral.
This is the first such API released on Linux to address a number of important problems, including: Because such hardware varies widely in capabilities and restrictions, and is used in embedded environments where space is at a premium, the gadget driver is often configured at compile time to work with endpoints supported by one particular controller.
One of the standards for cable modem interoperability even specifies the use of this ethernet model as one of two mandatory options. It may be suspended and resumed several times before being disconnected. Drivers for functions, configurations, or gadgets will then copy IDs from the string table to the appropriate descriptors and string table for other languages. You can generate a current version of that yourself directly with commands like "make pdfdocs", or use a pre-generated version which may not be as up-to-date as what you make from current kernel sources.
At this writing, there are people at work on drivers in this framework for several other USB device controllers, with plans to make many of them be widely available.
Drivers will normally be arranged so that just loading the gadget driver module or statically linking it into a Linux kernel allows the peripheral device to be enumerated, but some drivers will defer enumeration until some higher level component like a user mode daemon enables it. 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.
Discussions, patches, and similar work should be on the linux-usb-devel mailing list for now.
Near-term plans include converting all of them, except for gadgetfs. It's easy to backport current 2.
USB/Linux USB Layers/GadgetFs
The gadget API does support such drivers. The endpoint maxpacket field is updated according to the chosen descriptor. These utilities include endpoint autoconfiguration. The pxa allows only configurations 1, 2, or 3.
Gadgetfe Drivers At this writing there are several public "gadget drivers", each implementing a single common USB function so it will work with virtually any USB peripheral controller.
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