From: Daniel Drake <dsd@gentoo.org>

usbutils: print descriptor even if usb_open() fails

lsusb refuses to dump descriptors if usb_open() failed, whereas the core
of the information that is printed is available without a device handle at
all.

With libusb-0.1, if the device can only be opened for read access,
"lsusb -v" still prints descriptor info along with some error messages
for the failed control messages and so on. With libusb-compat-0.1,
usb_open() fails here and lsusb simply prints "Couldn't open device"

This patch makes it print the same available descriptor info even if
usb_open() fails.

With libusb-compat-0.1, usb_open() will fail if you do not have write access
to the device. I regard it as a bug that libusb-0.1 succeeds and returns a
device handle in this situation, because the handle is effectively useless
unless you have write access (all handle-based operations will fail).

It's unfortunate that this means new compat layer is diverging a little
from libusb-0.1 behaviour, but I don't think it's worth trying to clone
this behaviour. Please consider this for the next usbutils release.

Index: usbutils-0.73/ChangeLog
===================================================================
--- usbutils-0.73.orig/ChangeLog
+++ usbutils-0.73/ChangeLog
@@ -1,3 +1,8 @@
+2008-06-13 Daniel Drake <dsd@gentoo.org>
+	* lsusb.c: Dump descriptor information even if we don't get a
+	  device handle. Improves compatibility with
+	  libusb-1.0 and libusb-compat-0.1.
+
 2007-10-23 David Brownell <dbrownell@users.sourceforge.net>
 	* lsusb.c: Stop hiding unrecognized/misplaced class specific
 	  descriptors.  Don't require compressed format for usb.ids
Index: usbutils-0.73/lsusb.c
===================================================================
--- usbutils-0.73.orig/lsusb.c
+++ usbutils-0.73/lsusb.c
@@ -139,6 +139,11 @@ static int get_string(struct usb_dev_han
 {
 	int ret;
 
+	if (!dev) {
+		buf[0] = 0;
+		return 0;
+	}
+
 	if (id) {
 		ret = usb_get_string_simple(dev, id, buf, size);
 		if (ret <= 0) {
@@ -2069,6 +2074,12 @@ static void dump_hid_device(struct usb_d
 	if (!do_report_desc)
 		return;
 
+	if (!dev) {
+		printf( "         Report Descriptors: \n"
+			"           ** UNAVAILABLE **\n");
+		return;
+	}
+
 	for (i = 0; i < buf[5]; i++) {
 		/* we are just interested in report descriptors*/
 		if (buf[6+3*i] != USB_DT_REPORT)
@@ -2648,28 +2659,31 @@ static void dumpdev(struct usb_device *d
 
 	otg = wireless = 0;
 	udev = usb_open(dev);
-	if (udev) {
-		dump_device(udev, &dev->descriptor);
-		if (dev->descriptor.bcdUSB >= 0x0250)
-			wireless = do_wireless(udev);
-		if (dev->config) {
-			otg = do_otg(&dev->config[0]) || otg;
-			for (i = 0; i < dev->descriptor.bNumConfigurations;
-					i++) {
-				dump_config(udev, &dev->config[i]);
-			}
-		}
-		if (dev->descriptor.bDeviceClass == USB_CLASS_HUB)
-			do_hub(udev, dev->descriptor.bDeviceProtocol);
-		if (dev->descriptor.bcdUSB >= 0x0200) {
-			do_dualspeed(udev);
-			do_debug(udev);
-		}
+	if (!udev)
+		fprintf(stderr, "Couldn't open device, some information "
+			"will be missing\n");
+
+	dump_device(udev, &dev->descriptor);
+	if (dev->descriptor.bcdUSB >= 0x0250)
+		wireless = do_wireless(udev);
+	if (dev->config) {
+		otg = do_otg(&dev->config[0]) || otg;
+		for (i = 0; i < dev->descriptor.bNumConfigurations;
+				i++) {
+			dump_config(udev, &dev->config[i]);
+		}
+	}
+	if (udev && dev->descriptor.bDeviceClass == USB_CLASS_HUB)
+		do_hub(udev, dev->descriptor.bDeviceProtocol);
+	if (udev && dev->descriptor.bcdUSB >= 0x0200) {
+		do_dualspeed(udev);
+		do_debug(udev);
+	}
+	if (udev)
 		dump_device_status(udev, otg, wireless);
+
+	if (udev)
 		usb_close(udev);
-	}
-	else
-		fprintf(stderr, "Couldn't open device\n");
 }
 
 /* ---------------------------------------------------------------------- */