/* usb-try-discon -- try to claim a USB mass-storage interface */

#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <fcntl.h>
#include <errno.h>
#include <sys/ioctl.h>

#include <linux/usbdevice_fs.h>
#define USBDEVFS_TRY_DISCONNECT        _IO('U', 26)


int main(int argc, char **argv)
{
	const char *filename;
	unsigned intf;
	int fd;
	int rc;
	int c;
	struct usbdevfs_ioctl uioctl;

	if (argc != 3) {
		fprintf(stderr, "Usage: usb-try-discon devpath intf-num\n");
		return 1;
	}
	filename = argv[1];
	intf = atoi(argv[2]);

	fd = open(filename, O_WRONLY);
	if (fd < 0) {
		perror("Error opening device file");
		return 1;
	}

	printf("Trying to disconnect driver of %s interface %d\n",
			filename, intf);
	uioctl.ifno = intf;
	uioctl.ioctl_code = USBDEVFS_TRY_DISCONNECT;
	uioctl.data = NULL;
	rc = ioctl(fd, USBDEVFS_IOCTL, &uioctl);
	if (rc < 0 && errno == ENODATA) {
		printf("No driver was connected.\n");
	} else if (rc < 0) {
		perror("Error in ioctl");
		return 1;
	} else {
		printf("Disconnect successful\n");
	}

	printf("Trying to claim the interface\n");
	rc = ioctl(fd, USBDEVFS_CLAIMINTERFACE, &intf);
	if (rc < 0) {
		perror("Error in ioctl");
		return 1;
	}
	printf("Claim successful\n");

	printf("Press Enter to continue...");
	do {
		c = getc(stdin);
	} while (c != '\n' && c != EOF);

	printf("Releasing interface\n");
	rc = ioctl(fd, USBDEVFS_RELEASEINTERFACE, &intf);
	if (rc < 0) {
		perror("Error in ioctl");
		return 1;
	}
	printf("Release successful\n");

	close(fd);
	return 0;
}