libusb20_dev_open3
Open a usb device to retrieve descriptors and initiate transfers
Usage
library “libusb”
#include <libusb20.h>
int
libusb20_dev_open(struct libusb20_device *pdev, uin16_t transfer_max);
Overview
The libusb20_dev_open function opens a USB device to retrieve descriptors and initiate transfers. libusb20_dev_open accepts a pointer as pdev to a libusb20_device obtained from libusb20_be_device_foreach. A zero for transfer_max limits the device to only control transfers. Call libusb20_dev_close(3) to free resources taken by the open device handle.
Return values
libusb20_dev_open returns one of the following to report success or failure:
- LIBUSB20_SUCCESS,
-
The operation succeeds.
- LIBUSB20_ERROR_BUSY,
-
The device is in use elsewhere.
- LIBUSB20_ERROR_ACCESS,
-
A permissions issue.
- LIBUSB20_ERROR_NO_DEVICE,
-
The device detached.
- LIBUSB20_ERROR_NO_MEM
-
The library couldn't allocate memory.
Errors not listed here may be found in libusb20(3) and ⟨libusb20.h⟩.
Examples
#include <libusb20.h>
struct libusb20_backend *be = libusb20_be_alloc_default(NULL);
struct libusb20_device *device = NULL;
while ( (device = libusb20_be_device_foreach(be, device)) != NULL ) {
if (libusb20_dev_open(device, 0) == LIBUSB20_SUCCESS) {
/* do something */
libusb20_dev_close(device);
}
}
libusb20_be_free(be);
Releases
36 releases since FreeBSD 8.3-RELEASE; the text changed 27 times.