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