getddesc.c : test code of GET_DESCRIPTOR(DEVICE)

// cc getddesc.c -Wall -O2 -lusb
#include <stdio.h>
#include <string.h>
#include <usb.h>

static void dump(unsigned char *buf, int len)
{
	int i;

	for (i = 0; i < len; i++)
		printf("%02x ", buf[i]);

	printf("\n");
}

static void do_test(usb_dev_handle *dh, int i)
{
	unsigned char buf[256];
	int err;

	memset(buf, 0, sizeof(buf));
	err = usb_control_msg(dh, 0x80, 0x06, 0x0100, 0x0000, (char *)buf, i, 5000);
	printf("%d: ", i);
	dump(buf, err);
}

static void do_action(struct usb_device *dev)
{
	usb_dev_handle *dh;
	int i;

	/* open device */
	dh = usb_open(dev);
	if (dh == NULL) {
		printf("usb_open NULL\n");
		goto fin0;
	}

	/* test */
	for (i = 0x20; i >= 0; i--)
		do_test(dh, i);

//fin1:
	usb_close(dh);
fin0:
	return;
}

int main(int argc, char *argv[])
{
	struct usb_bus *bus;
	struct usb_device *dev;
	int found, bnum, dnum, vid, pid;

	if (argc < 3) {
		printf("%s [idVendor] [idProduct]\n", argv[0]);
		goto fin0;
	}

	vid = strtol(argv[1], NULL, 0);
	pid = strtol(argv[2], NULL, 0);

	/* initialize libusb */
	usb_init();
	usb_find_busses();
	usb_find_devices();

	/* no device as default */
	found = 0;

	/* find device */
	for (bus = usb_get_busses(), bnum = 0; bus != NULL;
	     bus = bus->next, bnum++) {
		for (dev = bus->devices, dnum = 0; dev != NULL;
		     dev = dev->next, dnum++) {
			if (dev->descriptor.idVendor == vid &&
			    dev->descriptor.idProduct == pid) {
				found = 1;
				goto found;
			}
		}
	}
found:
	/* do action when device is found */
	if (found) {
		printf("device at %d:%d\n", bnum, dnum);
		do_action(dev);
	} else {
		printf("device not found\n");
	}
fin0:
	return 0;
}