usbd_attach()

Attach to a USB device

Synopsis:

#include <sys/usbdi.h>

int usbd_attach( struct usbd_connection *connection, 
                 usbd_device_instance_t *instance, 
                 size_t extra, 
                 struct usbd_device **device );

Arguments:

connection

An opaque handle that identifies the USB stack (from usbd_connect()).

instance

Describes which device you wish to attach to.

extra

The size of additional memory you'd like allocated with the device. You can use usbd_device_extra() later to get a pointer to this additional memory. Typically, the class driver would store various status/config/device-specific details in here (if needed).

device

An opaque handle used to identify the device in later calls.

Library:

libusbdi

Description:

You use the usbd_attach() function to attach to a USB device. Typically, you do this out of the insertion callback (made when the device matched your filter), which will give you the connection and instance parameters involved. The insertion callback is prototyped as follows:

void (*insertion)(struct usbd_connection *, usbd_device_instance_t *instance)

The usbd_device_instance_t structure looks like this:

typedef struct usbd_device_instance {
    _uint8                    path;
    _uint8                    devno;
    _uint16                   generation;
    usbd_device_ident_t       ident;
    _uint32                   config;
    _uint32                   iface;
    _uint32                   alternate;
} usbd_device_instance_t;

Looping

Another way to attach is to loop and attach to all devices (in which case you build the instance yourself). For example:

for (busno = 0; busno < 10; ++busno) {
    for (devno = 0; devno < 64; ++devno) {
        memset(&instance, USBD_CONNECT_WILDCARD, sizeof(usbd_device_instance_t));
        instance.path = busno, instance.devno = devno;
        if (usbd_attach(connection, &instance, 0, &device) == EOK) {
          ......
        }
    }
}

The degree of "attachedness" depends on how you connected:

• If you specified insertion/removal callback functions, then you'll get exclusive access to the device and can make I/O to it.
• If you didn't use callbacks and you attached as in the loop above, you get shared access, so you can only read device configuration.

Returns:

EOK

Success.

ENODEV

Specified device doesn't exist. If in a loop, then there's nothing at that devno. If from a callback, then the device has since been removed.

EBUSY

A shared/exclusive conflict.

ENOMEM

No memory for internal device structures.

Classification:

QNX Neutrino, QNX 4

See also:

usbd_connect(), usbd_detach(), usbd_device_extra(), usbd_disconnect()