Linux MTP driver: Detect devices that have MTP interfaces even if their USB ids are not known

src/calibre/devices/mtp/unix/driver.py

@@ -13,7 +13,7 @@ from collections import namedtuple
 from functools import partial
 
 from calibre import prints, as_unicode
-from calibre.constants import plugins
+from calibre.constants import plugins, islinux
 from calibre.ptempfile import SpooledTemporaryFile
 from calibre.devices.errors import OpenFailed, DeviceError, BlacklistedDevice
 from calibre.devices.mtp.base import MTPDeviceBase, synchronous, debug
@@ -44,6 +44,17 @@ class MTP_DEVICE(MTPDeviceBase):
         self.blacklisted_devices = set()
         self.ejected_devices = set()
         self.currently_connected_dev = None
+        self._is_device_mtp = None
+        if islinux:
+            from calibre.devices.mtp.unix.sysfs import MTPDetect
+            self._is_device_mtp = MTPDetect()
+
+    def is_device_mtp(self, d, debug=None):
+        ''' Returns True iff the _is_device_mtp check returns True and libmtp
+        is able to probe the device successfully. '''
+        if self._is_device_mtp is None: return False
+        return (self._is_device_mtp(d, debug=debug) and
+                self.libmtp.is_mtp_device(d.busnum, d.devnum))
 
     def set_debug_level(self, lvl):
         self.libmtp.set_debug_level(lvl)
@@ -77,7 +88,9 @@ class MTP_DEVICE(MTPDeviceBase):
         for d in devs:
             ans = cache.get(d, None)
             if ans is None:
-                ans = (d.vendor_id, d.product_id) in self.known_devices
+                ans = (
+                    (d.vendor_id, d.product_id) in self.known_devices or
+                    self.is_device_mtp(d))
                 cache[d] = ans
             if ans:
                 return d
@@ -95,12 +108,13 @@ class MTP_DEVICE(MTPDeviceBase):
                 err = 'startup() not called on this device driver'
             p(err)
             return False
-        devs = [d for d in devices_on_system if (d.vendor_id, d.product_id)
-                in self.known_devices and d.vendor_id != APPLE]
+        devs = [d for d in devices_on_system if
+            ( (d.vendor_id, d.product_id) in self.known_devices or
+               self.is_device_mtp(d, debug=p)) and d.vendor_id != APPLE]
         if not devs:
-            p('No known MTP devices connected to system')
+            p('No MTP devices connected to system')
             return False
-        p('Known MTP devices connected:')
+        p('MTP devices connected:')
         for d in devs: p(d)
 
         for d in devs:

src/calibre/devices/mtp/unix/libmtp.c

@@ -662,13 +662,6 @@ is_mtp_device(PyObject *self, PyObject *args) {
 
     if (!PyArg_ParseTuple(args, "ii", &busnum, &devnum)) return NULL;
 
-    /*
-     * LIBMTP_Check_Specific_Device does not seem to work at least on my linux
-     * system. Need to investigate why later. Most devices are in the device
-     * table so this is not terribly important.
-     */
-    /* LIBMTP_Set_Debug(LIBMTP_DEBUG_ALL); */
-    /* printf("Calling check: %d %d\n", busnum, devnum); */
     Py_BEGIN_ALLOW_THREADS;
     ans = LIBMTP_Check_Specific_Device(busnum, devnum);
     Py_END_ALLOW_THREADS;

src/calibre/devices/mtp/unix/sysfs.py

@@ -0,0 +1,53 @@
+#!/usr/bin/env python
+# vim:fileencoding=UTF-8:ts=4:sw=4:sta:et:sts=4:fdm=marker:ai
+from __future__ import (unicode_literals, division, absolute_import,
+                        print_function)
+
+__license__   = 'GPL v3'
+__copyright__ = '2013, Kovid Goyal <kovid at kovidgoyal.net>'
+__docformat__ = 'restructuredtext en'
+
+import os, glob
+
+class MTPDetect(object):
+
+    SYSFS_PATH = os.environ.get('SYSFS_PATH', '/sys')
+
+    def __init__(self):
+        self.base = os.path.join(self.SYSFS_PATH, 'subsystem', 'usb', 'devices')
+        if not os.path.exists(self.base):
+            self.base = os.path.join(self.SYSFS_PATH, 'bus', 'usb', 'devices')
+        self.ok = os.path.exists(self.base)
+
+    def __call__(self, dev, debug=None):
+        '''
+        Check if the device has an interface named "MTP" using sysfs, which
+        avoids probing the device.
+        '''
+        if not self.ok: return False
+
+        def read(x):
+            try:
+                with open(x, 'rb') as f:
+                    return f.read()
+            except EnvironmentError:
+                pass
+
+        ipath = os.path.join(self.base, '{0}-*/{0}-*/interface'.format(dev.busnum))
+        for x in glob.glob(ipath):
+            raw = read(x)
+            if not raw or raw.strip() != b'MTP': continue
+            raw = read(os.path.join(os.path.dirname(os.path.dirname(x)),
+                                    'devnum'))
+            try:
+                if raw and int(raw) == dev.devnum:
+                    if debug is not None:
+                        debug('Unknown device {0} claims to be an MTP device'
+                              .format(dev))
+                    return True
+            except (ValueError, TypeError):
+                continue
+
+        return False
+
+