[libusb] [PATCH] linux: Assume usbfs path = /dev/bus/usb when using UDEV

[Hans de G. <hde...@re...>]

On some exotic hardware, e.g. HP ProLiant Moonshot Cartridge servers there
are no usb controllers, so no usb devices at all.

In this case currently libusb_init will fail, because find_usbfs_path
fails. Many apps don't handle this gracefully, and even if they do not crash
the result still is not pretty, e.g.:

unable to initialize libusb: -99

Where one simply would expect empty output.

Since on systems using udev the usbfs path should always be /dev/bus/usb
(as that gets created by udev), simply assume /dev/bus/usb when build with
USE_UDEV and the path cannot be found in the traditional way.

Signed-off-by: Hans de Goede <hde...@re...>
---
 libusb/os/linux_usbfs.c | 8 ++++++++
 libusb/version_nano.h   | 2 +-
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/libusb/os/linux_usbfs.c b/libusb/os/linux_usbfs.c
index 5e9b666..ac9cb54 100644
--- a/libusb/os/linux_usbfs.c
+++ b/libusb/os/linux_usbfs.c
@@ -307,6 +307,14 @@ static const char *find_usbfs_path(void)
 		}
 	}
 
+/* On udev based systems without any usb-devices /dev/bus/usb will not
+ * exist. So if we've not found anything and we're using udev for hotplug
+ * simply assume /dev/bus/usb rather then making libusb_init fail. */
+#if defined(USE_UDEV)
+	if (ret == NULL)
+		ret = "/dev/bus/usb";
+#endif
+
 	if (ret != NULL)
 		usbi_dbg("found usbfs at %s", ret);
 
diff --git a/libusb/version_nano.h b/libusb/version_nano.h
index a8bf988..d8030b5 100644
--- a/libusb/version_nano.h
+++ b/libusb/version_nano.h
@@ -1 +1 @@
-#define LIBUSB_NANO 10967
+#define LIBUSB_NANO 10968
-- 
2.3.4