1 ====================== 2 FunctionFS Descriptors 3 ====================== 4 5 Some of the descriptors that can be written to the FFS gadget are 6 described below. Device and configuration descriptors are handled 7 by the composite gadget and are not written by the user to the 8 FFS gadget. 9 10 Descriptors are written to the "ep0" file in the FFS gadget 11 following the descriptor header. 12 13 .. kernel-doc:: include/uapi/linux/usb/functionfs.h 14 :doc: descriptors 15 16 Interface Descriptors 17 --------------------- 18 19 Standard USB interface descriptors may be written. The class/subclass of the 20 most recent interface descriptor determines what type of class-specific 21 descriptors are accepted. 22 23 Class-Specific Descriptors 24 -------------------------- 25 26 Class-specific descriptors are accepted only for the class/subclass of the 27 most recent interface descriptor. The following are some of the 28 class-specific descriptors that are supported. 29 30 DFU Functional Descriptor 31 ~~~~~~~~~~~~~~~~~~~~~~~~~ 32 33 When the interface class is USB_CLASS_APP_SPEC and the interface subclass 34 is USB_SUBCLASS_DFU, a DFU functional descriptor can be provided. 35 The DFU functional descriptor is a described in the USB specification for 36 Device Firmware Upgrade (DFU), version 1.1 as of this writing. 37 38 .. kernel-doc:: include/uapi/linux/usb/functionfs.h 39 :doc: usb_dfu_functional_descriptor
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