Belkin F8E211 Guia do Utilizador descarregar pdf (Página 76)

usbd

parse

(ROOT)

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

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

(INTERFACE) - ..... (INTERFACE)

(ENDPOINT) - ..... (ENDPOINT)

Any vendor-speciﬁc or class-speciﬁc descriptors that are embedded into the standard

descriptor output are also inserted into this tree at the appropriate point.

Although a descriptor for endpoint 0 (control) isn’t present on the wire, one is

constructed and placed in the tree (to simplify enumeration within the class driver).

You use type for specifying the type of descriptor to ﬁnd; index is the nth occurrence.

Note that type 0 will match any descriptor type; you can use it to retrieve any

embedded class or vendor-speciﬁc descriptors if you don’t know their type.

Here’s an example that will walk all endpoints for an interface:

for (eix = 0; (desc = usbd_parse_descriptors(device, ifc, USB_DESC_ENDPOINT,

eix, &ept)) != NULL; ++eix)

;

where ifc is the appropriate (INTERFACE) node (found by a previous call to

usbd

parse

descriptors() or usbd

interface

descriptor().

Returns:

A pointer to the descriptor on success, or NULL on error.

Classiﬁcation:

QNX Neutrino, QNX 4

Safety

Cancellation point No

Interrupt handler No

Signal handler No

Thread Yes

See also:

usbd

args

lookup(), usbd

conﬁguration

descriptor(), usbd

descriptor(),

usbd

device

lookup(), usbd

device

extra(), usbd

device

descriptor(),

usbd

endpoint

descriptor(), usbd

hcd

info(), usbd

hub

descriptor(),

usbd

interface

descriptor(), usbd

languages

descriptor(), usbd

string(),

usbd

urb

status()

62 Chapter 4 • USB Library Reference September 10, 2007

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