Usb descriptor definition (.dsc) files, Structure, Usb d – Teledyne LeCroy USB Chief - File Based Decode Manual User Manual

Page 29: Dsc) f, Escriptor, Efinition, Iles

OMPUTER

CCESS

ECHNOLOGY

ORPORATION

USB D

ESCRIPTOR

EFINITION

DSC

) F

ILES

Reference Manual

USB D

ESCRIPTOR

EFINITION

(.dsc) F

ILES

Descriptor definition (.dsc) files are used to configure decoding of class- or vendor-
specific descriptors of any protocol. A .dsc file is a set of instructions that contains
definitions that describe, in USB-specific terms, how to take blocks of data and
break them into fields with consecutive decoding of each field. The descriptor def-
inition files are text-based files that are identifiable by their .dsc extension. Custom-
ized decoding of USB descriptors is possible by editing or creating new definition
files.

The .dsc files work in conjunction with .req files in order to display descriptor in-
formation in a trace. A descriptor can be referred to by its

DescriptorType

when a

GET_DESCRIPTOR

standard request (or any class- or vendor-specific

Get

SetDescriptor

request, such as

GET_HUB_DESCRIPTOR

) is executed.

Also, when a

CONFIGURATION

descriptor is requested by the

GET_DESCRIPTOR

standard request, a set of descriptors is supposed to be

returned by the USB device. This includes some standard descriptors (e.g.,

INTERFACE

and

ENDPOINT

) and also can include class- and vendor-specific de-

scriptors. The .dsc definitions will work for both of those cases, using the

DescriptorType

values and/or some other defined values, such as

DescriptorSubtype

ClassCode

and

Subclasscode

This document describes the components of a .dsc file and the format for writing or
editing a .dsc file.

Please refer to the Universal Serial Bus Specification, version 1.1 for details about
USB protocol. The USB specification is available from the USB Implementers
Forum (USB-IF) at http://www.usb.org/.

Structure

Descriptor definition files are structured very similarly to request definition files;
however, a .dsc file can contain multiple descriptor definitions (inlcuding the
header,

AllOffsets

, and

Offset

structures), whereas a request file can contain

only one set of definitions.

Here is the basic structure for a .dsc file:

DescriptorName=<name>
DescriptorType=<wValue>
[DescriptorSubtype=< ? >]

opt

[ClassCode=<class code>]

opt

[SubclassCode=<subclass code>]

opt