Belkin F8E211 Guida Utente Scaricare il pdf (Pagina 22)

class of device, just as if they’d been started by the enumerator. When a device is

removed, the enumerator will shut down the class driver.

For more information about device enumeration, see the Controlling How Neutrino

Starts chapter of the Neutrino User’s Guide.

How a class driver works

A class driver typically performs the following operations:

1 Connect to the USB stack (usbd

connect()) and provide two callbacks: one for

insertion and one for removal.

2 In the insertion callback:

2a Connect to the USB device (usbd

attach()).

2b Get descriptors (usbd

descriptor()).

2c Select the conﬁguration (usbd

select

conﬁg()) and interface

(usbd

select

interface()).

2d Set up communications pipes to the appropriate endpoint

(usbd

open

pipe()).

3 In the removal callback, detach from the USB device (usbd

detach()).

4 Set up all data communications (e.g. reading and writing data, sending and

receiving control information, etc.) via the usbd

setup

*() functions

(usbd

setup

bulk(), usbd

setup

interrupt(), etc.).

5 Initiate data transfer using the usbd

io() function (with completion callbacks if

required).

In this context, the term “pipe” is a USB-speciﬁc term that has nothing to do with

standard POSIX “pipes” (as used, for example, in the command line

ls | more). In

USB terminology, a “pipe” is simply a handle; something that identiﬁes a connection

to an endpoint.

8 Chapter 2 • Overview September 10, 2007

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Belkin F8E211 Guida Utente Pagina 22

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