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