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- ======================
- FunctionFS Descriptors
- ======================
- Some of the descriptors that can be written to the FFS gadget are
- described below. Device and configuration descriptors are handled
- by the composite gadget and are not written by the user to the
- FFS gadget.
- Descriptors are written to the "ep0" file in the FFS gadget
- following the descriptor header.
- .. kernel-doc:: include/uapi/linux/usb/functionfs.h
- :doc: descriptors
- Interface Descriptors
- ---------------------
- Standard USB interface descriptors may be written. The class/subclass of the
- most recent interface descriptor determines what type of class-specific
- descriptors are accepted.
- Class-Specific Descriptors
- --------------------------
- Class-specific descriptors are accepted only for the class/subclass of the
- most recent interface descriptor. The following are some of the
- class-specific descriptors that are supported.
- DFU Functional Descriptor
- ~~~~~~~~~~~~~~~~~~~~~~~~~
- When the interface class is USB_CLASS_APP_SPEC and the interface subclass
- is USB_SUBCLASS_DFU, a DFU functional descriptor can be provided.
- The DFU functional descriptor is a described in the USB specification for
- Device Firmware Upgrade (DFU), version 1.1 as of this writing.
- .. kernel-doc:: include/uapi/linux/usb/functionfs.h
- :doc: usb_dfu_functional_descriptor
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