Linux device detection: Parse /proc/bus/usb/devices directly instead of using libusb

src/calibre/devices/scanner.py

@@ -5,10 +5,9 @@ Device scanner that fetches list of devices on system ina  platform dependent
 manner.
 '''
 
-import sys
+import sys, re, os
 
 from calibre import iswindows, isosx, plugins
-from calibre.devices import libusb
 
 osx_scanner = win_scanner = linux_scanner = None
 
@@ -22,16 +21,38 @@ elif isosx:
         osx_scanner = plugins['usbobserver'][0].get_usb_devices
     except:
         raise RuntimeError('Failed to load the usbobserver plugin: %s'%plugins['usbobserver'][1])
-else:
-    linux_scanner = libusb.get_devices
+
+_usb_re = re.compile(r'Vendor\s*=\s*([0-9a-fA-F]+)\s+ProdID\s*=\s*([0-9a-fA-F]+)\s+Rev\s*=\s*([0-9a-fA-f.]+)')
+_DEVICES = '/proc/bus/usb/devices'
+
+
+def linux_scanner():
+    raw = open(_DEVICES).read()
+    devices = []
+    device = None
+    for x in raw.splitlines():
+        x = x.strip()
+        if x.startswith('T:'):
+            if device:
+                devices.append(device)
+            device = []
+        if device is not None and x.startswith('P:'):
+            match = _usb_re.search(x)
+            if match is not None:
+                ven, prod, bcd = match.group(1), match.group(2), match.group(3)
+                ven, prod, bcd = int(ven, 16), int(prod, 16), int(bcd.replace('.', ''), 16)
+                device = [ven, prod, bcd]
+    if device:
+        devices.append(device)
+    return devices
 
 class DeviceScanner(object):
 
     def __init__(self, *args):
         if isosx and osx_scanner is None:
             raise RuntimeError('The Python extension usbobserver must be available on OS X.')
-        if not (isosx or iswindows) and not libusb.has_library():
-            raise RuntimeError('DeviceScanner requires libusb to work.')
+        if not (isosx or iswindows) and not os.access(_DEVICES, os.R_OK):
+            raise RuntimeError('DeviceScanner requires %s to work.'%_DEVICES)
         self.scanner = win_scanner if iswindows else osx_scanner if isosx else linux_scanner
         self.devices = []