Add some examples about how to use FreeBSD's libusb20 in your own

code.

share/examples/Makefile

@@ -20,6 +20,7 @@ LDIRS=	BSD_daemon \
 	ipfw \
 	jails \
 	kld \
+	libusb20 \
 	libvgl \
 	mdoc \
 	netgraph \
@@ -110,6 +111,12 @@ XFILES=	BSD_daemon/FreeBSD.pfa \
 	kld/syscall/module/syscall.c \
 	kld/syscall/test/Makefile \
 	kld/syscall/test/call.c \
+	libusb20/Makefile \
+	libusb20/README \
+	libusb20/aux.c \
+	libusb20/aux.h \
+	libusb20/bulk.c \
+	libusb20/control.c \
 	libvgl/Makefile \
 	libvgl/demo.c \
 	mdoc/POSIX-copyright \

share/examples/libusb20/Makefile

@@ -0,0 +1,13 @@
+# $FreeBSD$
+TARGETS=	bulk control
+
+all: $(TARGETS)
+
+bulk: bulk.o aux.o
+	$(CC) $(CFLAGS) -o bulk bulk.o aux.o -lusb
+
+control: control.o aux.o
+	$(CC) $(CFLAGS) -o control control.o aux.o -lusb
+
+clean:
+	rm -f $(TARGETS) *.o *~

share/examples/libusb20/README

@@ -0,0 +1,42 @@
+As I dug my own way through the documentation of libusb 2.0 that ships
+with FreeBSD 8+ as the OS'es own USB library API, I noticed there are
+only few code examples around under /usr/src (namely, usbconfig
+itself).
+
+The libusb20(3) man page is a starting point, but it's a reference
+manual, nothing less, nothing more.  Using just a reference, it's not
+very easy to start writing your own code based on that.
+
+So I started writing my own examples, to "get a feeling" about how to
+use the library.  I covered two typical scenarios which are common for
+a number of devices.
+
+The first one is called "bulk", and uses bulk output (host to device)
+and input transfers to talk to an USB device.
+
+The second one is called "control", and can use both control output
+and input transfers, as well as so-called interrupt transfers.  The
+latter are used for data that are being reported frequently or
+repeatedly, like position updates from a pointing device (mouse).
+Despite of its name, the host has to poll devices for their interrupt
+transfers on each USB frame (i.e., each 1 ms).
+
+Recommended reading is the USB 3.0 specification (the older 2.0 one
+would do as well), to be found under
+
+http://www.usb.org/developers/docs/
+
+as well as documents for individual USB device classes where
+appropriate.
+
+Feel free to be liberal in the licensing of these examples: while the
+beer-ware license mandates to keep the license notice, this only
+applies to modifications of the original examples itself.  For
+copy&pasting (even a larger) piece of an example into your own work, I
+won't imply you have to reproduce the beer-ware license text there.
+Feel free to credit my name in your derived work if you want.
+
+Dresden, July 2012
+Joerg Wunsch <joerg@FreeBSD.org>
+
+# $FreeBSD$

share/examples/libusb20/aux.c

@@ -0,0 +1,120 @@
+/* ----------------------------------------------------------------------------
+ * "THE BEER-WARE LICENSE" (Revision 42) (by Poul-Henning Kamp):
+ * <joerg@FreeBSD.ORG> wrote this file.  As long as you retain this notice you
+ * can do whatever you want with this stuff. If we meet some day, and you think
+ * this stuff is worth it, you can buy me a beer in return.        Joerg Wunsch
+ * ----------------------------------------------------------------------------
+ *
+ * $FreeBSD$
+ */
+
+/*
+ * Helper functions common to all examples
+ */
+
+#include <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
+
+#include <libusb20.h>
+#include <libusb20_desc.h>
+
+#include "aux.h"
+
+/*
+ * Return a textual description for error "r".
+ */
+const char *
+usb_error(enum libusb20_error r)
+{
+  const char *msg = "UNKNOWN";
+
+  switch (r)
+    {
+    case LIBUSB20_SUCCESS:
+      msg = "success";
+      break;
+
+    case LIBUSB20_ERROR_IO:
+      msg = "IO error";
+      break;
+
+    case LIBUSB20_ERROR_INVALID_PARAM:
+      msg = "Invalid parameter";
+      break;
+
+    case LIBUSB20_ERROR_ACCESS:
+      msg = "Access denied";
+      break;
+
+    case LIBUSB20_ERROR_NO_DEVICE:
+      msg = "No such device";
+      break;
+
+    case LIBUSB20_ERROR_NOT_FOUND:
+      msg = "Entity not found";
+      break;
+
+    case LIBUSB20_ERROR_BUSY:
+      msg = "Resource busy";
+      break;
+
+    case LIBUSB20_ERROR_TIMEOUT:
+      msg = "Operation timed out";
+      break;
+
+    case LIBUSB20_ERROR_OVERFLOW:
+      msg = "Overflow";
+      break;
+
+    case LIBUSB20_ERROR_PIPE:
+      msg = "Pipe error";
+      break;
+
+    case LIBUSB20_ERROR_INTERRUPTED:
+      msg = "System call interrupted";
+      break;
+
+    case LIBUSB20_ERROR_NO_MEM:
+      msg = "Insufficient memory";
+      break;
+
+    case LIBUSB20_ERROR_NOT_SUPPORTED:
+      msg = "Operation not supported";
+      break;
+
+    case LIBUSB20_ERROR_OTHER:
+      msg = "Other error";
+      break;
+    }
+
+  return msg;
+}
+
+/*
+ * Print "len" bytes from "buf" in hex, followed by an ASCII
+ * representation (somewhat resembling the output of hd(1)).
+ */
+void
+print_formatted(uint8_t *buf, uint32_t len)
+{
+  int i, j;
+
+  for (j = 0; j < len; j += 16)
+    {
+      printf("%02x: ", j);
+
+      for (i = 0; i < 16 && i + j < len; i++)
+	printf("%02x ", buf[i + j]);
+      printf("  ");
+      for (i = 0; i < 16 && i + j < len; i++)
+	{
+	  uint8_t c = buf[i + j];
+	  if(c >= ' ' && c <= '~')
+	    printf("%c", (char)c);
+	  else
+	    putchar('.');
+	}
+      putchar('\n');
+    }
+}

share/examples/libusb20/aux.h

@@ -0,0 +1,15 @@
+/* ----------------------------------------------------------------------------
+ * "THE BEER-WARE LICENSE" (Revision 42) (by Poul-Henning Kamp):
+ * <joerg@FreeBSD.ORG> wrote this file.  As long as you retain this notice you
+ * can do whatever you want with this stuff. If we meet some day, and you think
+ * this stuff is worth it, you can buy me a beer in return.        Joerg Wunsch
+ * ----------------------------------------------------------------------------
+ *
+ * $FreeBSD$
+ */
+
+#include <stdint.h>
+#include <libusb20.h>
+
+const char *usb_error(enum libusb20_error r);
+void print_formatted(uint8_t *buf, uint32_t len);

share/examples/libusb20/bulk.c

@@ -0,0 +1,243 @@
+/* ----------------------------------------------------------------------------
+ * "THE BEER-WARE LICENSE" (Revision 42) (by Poul-Henning Kamp):
+ * <joerg@FreeBSD.ORG> wrote this file.  As long as you retain this notice you
+ * can do whatever you want with this stuff. If we meet some day, and you think
+ * this stuff is worth it, you can buy me a beer in return.        Joerg Wunsch
+ * ----------------------------------------------------------------------------
+ *
+ * $FreeBSD$
+ */
+
+/*
+ * Simple demo program to illustrate the handling of FreeBSD's
+ * libusb20.
+ *
+ * Issues a bulk output, and then requests a bulk input.
+ */
+
+/*
+ * Examples:
+ * Just list all VID:PID pairs
+ * ./bulk
+ *
+ * Say "hello" to an Atmel JTAGICEmkII.
+ * ./bulk -o 2 -i 0x82 -v 0x03eb -p 0x2103 0x1b 0 0 1 0 0 0 0x0e 1 0xf3 0x97
+ *
+ * Return the INQUIRY data of an USB mass storage device.
+ * (It's best to have the umass(4) driver unloaded while doing such
+ * experiments, and perform a "usbconfig reset" for the device if it
+ * gets stuck.)
+ * ./bulk -v 0x5e3 -p 0x723 -i 0x81 -o 2 0x55 0x53 0x42 0x43 1 2 3 4 31 12 0x80 0x24 0 0 0 0x12 0 0 0 36 0 0 0 0 0 0 0 0 0 0
+ */
+
+
+#include <limits.h>
+#include <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <sysexits.h>
+#include <unistd.h>
+
+#include <libusb20.h>
+#include <libusb20_desc.h>
+
+#include "aux.h"
+
+/*
+ * If you want to see the details of the internal datastructures
+ * in the debugger, unifdef the following.
+ */
+#ifdef DEBUG
+#  include <sys/queue.h>
+#  include "/usr/src/lib/libusb/libusb20_int.h"
+#endif
+
+#define BUFLEN 64
+
+#define TIMEOUT 5000 		/* 5 s */
+
+int in_ep, out_ep;		/* endpoints */
+uint8_t out_buf[BUFLEN];
+uint16_t out_len;
+
+static void
+doit(struct libusb20_device *dev)
+{
+  int rv;
+
+  /*
+   * Open the device, allocating memory for two possible (bulk or
+   * interrupt) transfers.
+   *
+   * If only control transfers are intended (via
+   * libusb20_dev_request_sync()), transfer_max can be given as 0.
+   */
+  if ((rv = libusb20_dev_open(dev, 2)) != 0)
+    {
+      fprintf(stderr, "libusb20_dev_open: %s\n", usb_error(rv));
+      return;
+    }
+
+  /*
+   * If the device has more than one configuration, select the desired
+   * one here.
+   */
+  if ((rv = libusb20_dev_set_config_index(dev, 0)) != 0)
+    {
+      fprintf(stderr, "libusb20_dev_set_config_index: %s\n", usb_error(rv));
+      return;
+    }
+
+  /*
+   * Two transfers have been requested in libusb20_dev_open() above;
+   * obtain the corresponding transfer struct pointers.
+   */
+  struct libusb20_transfer *xfr_out = libusb20_tr_get_pointer(dev, 0);
+  struct libusb20_transfer *xfr_in = libusb20_tr_get_pointer(dev, 1);
+
+  if (xfr_in == NULL || xfr_out == NULL)
+    {
+      fprintf(stderr, "libusb20_tr_get_pointer: %s\n", usb_error(rv));
+      return;
+    }
+
+  /*
+   * Open both transfers, the "out" one for the write endpoint, the
+   * "in" one for the read endpoint (ep | 0x80).
+   */
+  if ((rv = libusb20_tr_open(xfr_out, 0, 1, out_ep)) != 0)
+    {
+      fprintf(stderr, "libusb20_tr_open: %s\n", usb_error(rv));
+      return;
+    }
+  if ((rv = libusb20_tr_open(xfr_in, 0, 1, in_ep)) != 0)
+    {
+      fprintf(stderr, "libusb20_tr_open: %s\n", usb_error(rv));
+      return;
+    }
+
+  uint8_t in_buf[BUFLEN];
+  uint32_t rlen;
+
+  if (out_len > 0)
+    {
+      if ((rv = libusb20_tr_bulk_intr_sync(xfr_out, out_buf, out_len, &rlen, TIMEOUT))
+	  != 0)
+	{
+	  fprintf(stderr, "libusb20_tr_bulk_intr_sync (OUT): %s\n", usb_error(rv));
+	}
+      printf("sent %d bytes\n", rlen);
+    }
+
+  if ((rv = libusb20_tr_bulk_intr_sync(xfr_in, in_buf, BUFLEN, &rlen, TIMEOUT))
+      != 0)
+    {
+      fprintf(stderr, "libusb20_tr_bulk_intr_sync: %s\n", usb_error(rv));
+    }
+      printf("received %d bytes\n", rlen);
+      if (rlen > 0)
+	print_formatted(in_buf, rlen);
+
+  libusb20_tr_close(xfr_out);
+  libusb20_tr_close(xfr_in);
+
+  libusb20_dev_close(dev);
+}
+
+static void
+usage(void)
+{
+  fprintf(stderr,
+	  "Usage ./usb -i <IN_EP> -o <OUT_EP> -v <VID> -p <PID> [<outdata> ...\n]");
+  exit(EX_USAGE);
+}
+
+int
+main(int argc, char **argv)
+{
+  unsigned int vid = UINT_MAX, pid = UINT_MAX; /* impossible VID:PID */
+  int c;
+
+  while ((c = getopt(argc, argv, "i:o:p:v:")) != -1)
+    switch (c)
+      {
+      case 'i':
+	in_ep = strtol(optarg, NULL, 0);
+	break;
+
+      case 'o':
+	out_ep = strtol(optarg, NULL, 0);
+	break;
+
+      case 'p':
+	pid = strtol(optarg, NULL, 0);
+	break;
+
+      case 'v':
+	vid = strtol(optarg, NULL, 0);
+	break;
+
+      default:
+	usage();
+	break;
+      }
+  argc -= optind;
+  argv += optind;
+
+  if (vid != UINT_MAX || pid != UINT_MAX)
+    {
+      if (in_ep == 0 || out_ep == 0)
+	{
+	  usage();
+	}
+      if ((in_ep & 0x80) == 0)
+	{
+	  fprintf(stderr, "IN_EP must have bit 7 set\n");
+	  return (EX_USAGE);
+	}
+
+      if (argc > 0)
+	{
+	  for (out_len = 0; argc > 0 && out_len < BUFLEN; out_len++, argc--)
+	    {
+	      unsigned n = strtoul(argv[out_len], 0, 0);
+	      if (n > 255)
+		fprintf(stderr,
+			"Warning: data #%d 0x%0x > 0xff, truncating\n",
+			out_len, n);
+	      out_buf[out_len] = (uint8_t)n;
+	    }
+	  out_len++;
+	  if (argc > 0)
+	    fprintf(stderr,
+		    "Data count exceeds maximum of %d, ignoring %d elements\n",
+		    BUFLEN, optind);
+	}
+    }
+
+  struct libusb20_backend *be;
+  struct libusb20_device *dev;
+
+  if ((be = libusb20_be_alloc_default()) == NULL)
+    {
+      perror("libusb20_be_alloc()");
+      return 1;
+    }
+
+  dev = NULL;
+  while ((dev = libusb20_be_device_foreach(be, dev)) != NULL)
+    {
+      struct LIBUSB20_DEVICE_DESC_DECODED *ddp =
+      libusb20_dev_get_device_desc(dev);
+
+      printf("Found device %s (VID:PID = 0x%04x:0x%04x)\n",
+	     libusb20_dev_get_desc(dev),
+	     ddp->idVendor, ddp->idProduct);
+
+      if (ddp->idVendor == vid && ddp->idProduct == pid)
+	doit(dev);
+    }
+
+  libusb20_be_free(be);
+  return 0;
+}

share/examples/libusb20/control.c

@@ -0,0 +1,414 @@
+/* ----------------------------------------------------------------------------
+ * "THE BEER-WARE LICENSE" (Revision 42) (by Poul-Henning Kamp):
+ * <joerg@FreeBSD.ORG> wrote this file.  As long as you retain this notice you
+ * can do whatever you want with this stuff. If we meet some day, and you think
+ * this stuff is worth it, you can buy me a beer in return.        Joerg Wunsch
+ * ----------------------------------------------------------------------------
+ *
+ * $FreeBSD$
+ */
+
+/*
+ * Simple demo program to illustrate the handling of FreeBSD's
+ * libusb20.
+ *
+ * XXX
+ */
+
+/*
+ * Examples:
+ * Just list all VID:PID pairs
+ * ./control
+ *
+ * Standard device request GET_STATUS, report two bytes of status
+ * (bit 0 in the first byte returned is the "self powered" bit)
+ * ./control -v 0x3eb -p 0x2103 in std dev get_status 0 0 2
+ *
+ * Request input reports through the interrupt pipe from a mouse
+ * device (move the mouse around after issuing the command):
+ * ./control -v 0x093a -p 0x2516 -i 0x81
+ *
+ */
+
+
+#include <limits.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <sysexits.h>
+#include <unistd.h>
+
+#include <libusb20.h>
+#include <libusb20_desc.h>
+
+#include <sys/queue.h>
+
+/*
+ * If you want to see the details of the internal datastructures
+ * in the debugger, unifdef the following.
+ */
+#ifdef DEBUG
+#  include "/usr/src/lib/libusb/libusb20_int.h"
+#endif
+
+#define BUFLEN 64
+
+#define TIMEOUT 5000 		/* 5 s */
+
+int intr_ep;		/* endpoints */
+struct LIBUSB20_CONTROL_SETUP_DECODED setup;
+
+uint8_t out_buf[BUFLEN];
+uint16_t out_len;
+
+bool do_request;
+
+static void
+doit(struct libusb20_device *dev)
+{
+  int rv;
+
+  if (do_request)
+    printf("doit(): bmRequestType 0x%02x, bRequest 0x%02x, wValue 0x%04x, wIndex 0x%04x, wLength 0x%04x\n",
+	   setup.bmRequestType,
+	   setup.bRequest,
+	   setup.wValue,
+	   setup.wIndex,
+	   setup.wLength);
+
+  /*
+   * Open the device, allocating memory for two possible (bulk or
+   * interrupt) transfers.
+   *
+   * If only control transfers are intended (via
+   * libusb20_dev_request_sync()), transfer_max can be given as 0.
+   */
+  if ((rv = libusb20_dev_open(dev, 1)) != 0)
+    {
+      fprintf(stderr, "libusb20_dev_open: %s\n", usb_error(rv));
+      return;
+    }
+
+  /*
+   * If the device has more than one configuration, select the desired
+   * one here.
+   */
+  if ((rv = libusb20_dev_set_config_index(dev, 0)) != 0)
+    {
+      fprintf(stderr, "libusb20_dev_set_config_index: %s\n", usb_error(rv));
+      return;
+    }
+
+  uint8_t *data = 0;
+  uint16_t actlen;
+
+  if ((setup.bmRequestType & 0x80) != 0)
+    {
+      /* this is an IN request, allocate a buffer */
+      data = malloc(setup.wLength);
+      if (data == 0)
+	{
+	  fprintf(stderr,
+		  "Out of memory allocating %u bytes of reply buffer\n",
+		  setup.wLength);
+	  return;
+	}
+    }
+  else
+    data = out_buf;
+
+  if (do_request)
+    {
+      if ((rv = libusb20_dev_request_sync(dev, &setup, data,
+					  &actlen,
+					  TIMEOUT,
+					  0 /* flags */)) != 0)
+	{
+	  fprintf(stderr,
+		  "libusb20_dev_request_sync: %s\n", usb_error(rv));
+	}
+      printf("sent %d bytes\n", actlen);
+      if ((setup.bmRequestType & 0x80) != 0)
+	{
+	  print_formatted(data, (uint32_t)setup.wLength);
+	  free(data);
+	}
+    }
+
+  if (intr_ep != 0)
+    {
+      /*
+       * One transfer has been requested in libusb20_dev_open() above;
+       * obtain the corresponding transfer struct pointer.
+       */
+      struct libusb20_transfer *xfr_intr = libusb20_tr_get_pointer(dev, 0);
+
+      if (xfr_intr == NULL)
+	{
+	  fprintf(stderr, "libusb20_tr_get_pointer: %s\n", usb_error(rv));
+	  return;
+	}
+
+      /*
+       * Open the interrupt transfer.
+       */
+      if ((rv = libusb20_tr_open(xfr_intr, 0, 1, intr_ep)) != 0)
+	{
+	  fprintf(stderr, "libusb20_tr_open: %s\n", usb_error(rv));
+	  return;
+	}
+
+      uint8_t in_buf[BUFLEN];
+      uint32_t rlen;
+
+      if ((rv = libusb20_tr_bulk_intr_sync(xfr_intr, in_buf, BUFLEN, &rlen, TIMEOUT))
+	  != 0)
+	{
+	  fprintf(stderr, "libusb20_tr_bulk_intr_sync: %s\n", usb_error(rv));
+	}
+      printf("received %d bytes\n", rlen);
+      if (rlen > 0)
+	print_formatted(in_buf, rlen);
+
+      libusb20_tr_close(xfr_intr);
+    }
+
+  libusb20_dev_close(dev);
+}
+
+static void
+usage(void)
+{
+  fprintf(stderr,
+	  "Usage ./usb [-i <INTR_EP>] -v <VID> -p <PID> [dir type rcpt req wValue wIndex wLength [<outdata> ...]]\n");
+  exit(EX_USAGE);
+}
+
+static const char *reqnames[] =
+{
+  "get_status",
+  "clear_feature",
+  "res1",
+  "set_feature",
+  "res2",
+  "set_address",
+  "get_descriptor",
+  "set_descriptor",
+  "get_configuration",
+  "set_configuration",
+  "get_interface",
+  "set_interface",
+  "synch_frame",
+};
+
+static int
+get_req(const char *reqname)
+{
+  size_t i;
+  size_t l = strlen(reqname);
+
+  for (i = 0;
+       i < sizeof reqnames / sizeof reqnames[0];
+       i++)
+    if (strncasecmp(reqname, reqnames[i], l) == 0)
+      return i;
+
+  return strtoul(reqname, 0, 0);
+}
+
+
+static int
+parse_req(int argc, char **argv)
+{
+  int idx;
+  uint8_t rt = 0;
+
+  for (idx = 0; argc != 0 && idx <= 6; argc--, idx++)
+    switch (idx)
+      {
+      case 0:
+	/* dir[ection]: i[n] | o[ut] */
+	if (*argv[idx] == 'i')
+	  rt |= 0x80;
+	else if (*argv[idx] == 'o')
+	  /* nop */;
+	else
+	  {
+	    fprintf(stderr, "request direction must be \"in\" or \"out\" (got %s)\n",
+		    argv[idx]);
+	    return -1;
+	  }
+	break;
+
+      case 1:
+	/* type: s[tandard] | c[lass] | v[endor] */
+	if (*argv[idx] == 's')
+	  /* nop */;
+	else if (*argv[idx] == 'c')
+	  rt |= 0x20;
+	else if (*argv[idx] == 'v')
+	  rt |= 0x40;
+	else
+	  {
+	    fprintf(stderr,
+		    "request type must be one of \"standard\", \"class\", or \"vendor\" (got %s)\n",
+		    argv[idx]);
+	    return -1;
+	  }
+	break;
+
+      case 2:
+	/* rcpt: d[evice], i[nterface], e[ndpoint], o[ther] */
+	if (*argv[idx] == 'd')
+	  /* nop */;
+	else if (*argv[idx] == 'i')
+	  rt |= 1;
+	else if (*argv[idx] == 'e')
+	  rt |= 2;
+	else if (*argv[idx] == 'o')
+	  rt |= 3;
+	else
+	  {
+	    fprintf(stderr,
+		    "recipient must be one of \"device\", \"interface\", \"endpoint\", or \"other\" (got %s)\n",
+		    argv[idx]);
+	    return -1;
+	  }
+	setup.bmRequestType = rt;
+	break;
+
+      case 3:
+	setup.bRequest = get_req(argv[idx]);
+	break;
+
+      case 4:
+	setup.wValue = strtoul(argv[idx], 0, 0);
+	break;
+
+      case 5:
+	setup.wIndex = strtoul(argv[idx], 0, 0);
+	break;
+
+      case 6:
+	setup.wLength = strtoul(argv[idx], 0, 0);
+	break;
+      }
+
+  return argc;
+}
+
+
+int
+main(int argc, char **argv)
+{
+  unsigned int vid = UINT_MAX, pid = UINT_MAX; /* impossible VID:PID */
+  int c;
+
+  /*
+   * Initialize setup struct.  This step is required, and initializes
+   * internal fields in the struct.
+   *
+   * All the "public" fields are named exactly the way as the USB
+   * standard describes them, namely:
+   *
+   *	setup.bmRequestType: bitmask, bit 7 is direction
+   *	                              bits 6/5 is request type
+   *	                                       (standard, class, vendor)
+   *	                              bits 4..0 is recipient
+   *	                                       (device, interface, endpoint,
+   *	                                        other)
+   *	setup.bRequest:      the request itself (see get_req() for standard
+   *	                                         requests, or specific value)
+   *	setup.wValue:        a 16-bit value
+   *	setup.wIndex:        another 16-bit value
+   *	setup.wLength:       length of associated data transfer, direction
+   *	                     depends on bit 7 of bmRequestType
+   */
+  LIBUSB20_INIT(LIBUSB20_CONTROL_SETUP, &setup);
+
+  while ((c = getopt(argc, argv, "i:p:v:")) != -1)
+    switch (c)
+      {
+      case 'i':
+	intr_ep = strtol(optarg, NULL, 0);
+	break;
+
+      case 'p':
+	pid = strtol(optarg, NULL, 0);
+	break;
+
+      case 'v':
+	vid = strtol(optarg, NULL, 0);
+	break;
+
+      default:
+	usage();
+	break;
+      }
+  argc -= optind;
+  argv += optind;
+
+  if (vid != UINT_MAX || pid != UINT_MAX)
+    {
+      if (intr_ep != 0 && (intr_ep & 0x80) == 0)
+	{
+	  fprintf(stderr, "Interrupt endpoint must be of type IN\n");
+	  usage();
+	}
+
+      if (argc > 0)
+	{
+	  do_request = true;
+
+	  int rv = parse_req(argc, argv);
+	  if (rv < 0)
+	    return EX_USAGE;
+	  argc = rv;
+
+	  if (argc > 0)
+	    {
+	      for (out_len = 0; argc > 0 && out_len < BUFLEN; out_len++, argc--)
+		{
+		  unsigned n = strtoul(argv[out_len], 0, 0);
+		  if (n > 255)
+		    fprintf(stderr,
+			    "Warning: data #%d 0x%0x > 0xff, truncating\n",
+			    out_len, n);
+		  out_buf[out_len] = (uint8_t)n;
+		}
+	      out_len++;
+	      if (argc > 0)
+		fprintf(stderr,
+			"Data count exceeds maximum of %d, ignoring %d elements\n",
+			BUFLEN, optind);
+	    }
+	}
+    }
+
+  struct libusb20_backend *be;
+  struct libusb20_device *dev;
+
+  if ((be = libusb20_be_alloc_default()) == NULL)
+    {
+      perror("libusb20_be_alloc()");
+      return 1;
+    }
+
+  dev = NULL;
+  while ((dev = libusb20_be_device_foreach(be, dev)) != NULL)
+    {
+      struct LIBUSB20_DEVICE_DESC_DECODED *ddp =
+      libusb20_dev_get_device_desc(dev);
+
+      printf("Found device %s (VID:PID = 0x%04x:0x%04x)\n",
+	     libusb20_dev_get_desc(dev),
+	     ddp->idVendor, ddp->idProduct);
+
+      if (ddp->idVendor == vid && ddp->idProduct == pid)
+	doit(dev);
+    }
+
+  libusb20_be_free(be);
+  return 0;
+}