From d1d0c606fa773564e61cd2b8a837b7758529ef51 Mon Sep 17 00:00:00 2001
From: Kovid Goyal <kovid@kovidgoyal.net>
Date: Mon, 18 Jan 2016 22:04:56 +0530
Subject: [PATCH] More debug prints

---
 src/calibre/devices/winusb.py | 17 +++++++++++++----
 1 file changed, 13 insertions(+), 4 deletions(-)

diff --git a/src/calibre/devices/winusb.py b/src/calibre/devices/winusb.py
index 7669595a35..1c68ed6d31 100644
--- a/src/calibre/devices/winusb.py
+++ b/src/calibre/devices/winusb.py
@@ -813,11 +813,15 @@ def get_usb_info(usbdev, debug=False):  # {{{
     try:
         parent = next(iterancestors(usbdev.devinst))
     except StopIteration:
+        if debug:
+            prints('Cannot get USB info as device has no parent (was probably disconnected)')
         return ans
     for devinfo, parent_path in DeviceSet(guid=GUID_DEVINTERFACE_USB_HUB).interfaces():
         if devinfo.DevInst == parent:
             break
     else:
+        if debug:
+            prints('Cannot get USB info as parent of device is not a HUB')
         return ans
     for devlist, devinfo in DeviceSet(guid=GUID_DEVINTERFACE_USB_DEVICE).devices():
         if devinfo.DevInst == usbdev.devinst:
@@ -825,6 +829,10 @@ def get_usb_info(usbdev, debug=False):  # {{{
             break
     else:
         return ans
+    if not device_port:
+        if debug:
+            prints('Cannot get usb info as the SPDRP_ADDRESS property is not present int he registry (can happen with broken USB hub drivers)')
+        return ans
     handle = CreateFile(parent_path, GENERIC_READ | GENERIC_WRITE, FILE_SHARE_READ | FILE_SHARE_WRITE, None, OPEN_EXISTING, 0, None)
     try:
         buf, dd = get_device_descriptor(handle, device_port)
@@ -838,10 +846,11 @@ def get_usb_info(usbdev, debug=False):  # {{{
                         buf, ans[name] = get_device_string(handle, device_port, index, buf=buf)
                     except WindowsError as err:
                         if debug:
-                            if err.winerror == ERROR_GEN_FAILURE:
-                                prints('Failed to read %s from device, try rebooting the device' % name)
-                            else:
-                                prints('Failed to read %s from device, with error: %s' % (name, as_unicode(err)))
+                            # Note that I have observed that this fails
+                            # randomly after some time of my Kindle being
+                            # connected. Disconnecting and reconnecting causes
+                            # it to start working again.
+                            prints('Failed to read %s from device, with error: [%d] %s' % (name, err.winerror, as_unicode(err)))
     finally:
         CloseHandle(handle)
     return ans