Belkin F8E211 Guia do Utilizador descarregar pdf (Página 83)

 2006, QNX Software Systems GmbH & Co. KG. usbd parse descriptors()

Parse device descriptors looking for a speciﬁc entry

Synopsis:

#include <sys/usbdi.h>

usbd

descriptors t *usbd parse descriptors(

struct usbd

device *device,

struct usbd

desc node *root,

uint8 type, int index,

struct usbd

desc node **node );

Description:

When called the ﬁrst time, the usbd parse descriptors() function

loads all the descriptors from the USB device:

device

conﬁguration

interface

endpoint

hub

string

The function uses usdb

descriptor() to get each raw USB descriptor.

The data is then endian-ized, made alignment-safe, and built into an

in-memory tree structure to facilitate future parsing requests.

Each node in this tree is a

struct usbd desc node. The root parameter

lets you say where in the tree to begin parsing (NULL is base). The

node parameter tells you where a descriptor was found to root future

requests from.

The tree looks like this:

(ROOT)

(DEVICE) - (HUB) - (LANGUAGE TABLE)

(CONFIG) - ..... (CONFIG)

November 2, 2006 Chapter 4 USB Library Reference 71

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Belkin F8E211 Guia do Utilizador Página 83