Unable to connect a Nook Tablet running Cyanogenmod

[sgtrock]

I'm getting the following error:

calibre, version 1.25.0
ERROR: Error: Error communicating with device

Failed to upload file named: driveinfo.calibre to (u'Internal storage',): 2:PTP Layer error 2002: send_file_object_info(): Could not send object info.
2:Error 2002: PTP: General Error

Traceback (most recent call last):
File "site-packages/calibre/gui2/device.py", line 86, in run
File "site-packages/calibre/gui2/device.py", line 490, in _books
File "site-packages/calibre/devices/mtp/driver.py", line 208, in books
File "site-packages/calibre/devices/mtp/driver.py", line 180, in get_driveinfo
File "site-packages/calibre/devices/mtp/driver.py", line 170, in _update_drive_info
File "site-packages/calibre/devices/mtp/base.py", line 24, in synchronizer
File "site-packages/calibre/devices/mtp/unix/driver.py", line 355, in put_file
DeviceError: Failed to upload file named: driveinfo.calibre to (u'Internal storage',): 2:PTP Layer error 2002: send_file_object_info(): Could not send object info.
2:Error 2002: PTP: General Error

This is with calibre 1.25 on Debian testing. lsusb shows:

lsusb
Bus 004 Device 004: ID 18d1:685c Google Inc.

About Tablet tells me the following:

Model number:
Barnes & Noble Nook Tablet

Android version
4.2.2

Kernel version
3.0.62-g78545f4
build02@cyanogenmod #1

CyanogenMod version
10.1.0-acclaim

When I ask calibre to provide the device information, I get this:

Barnes & Noble Nook Tablet
Serial number: 2020240098xxxxxx
Manufacturer: Barnes & Noble
Model: Barnes & Noble Nook Tablet
ids: (4, 5, 6353, 26716, u'2020240098xxxxxx')
Device version: 1.0
Storage:
[{'capacity': 8003858432L,
'freespace_bytes': 8003850240L,
'freespace_objects': 1073741824L,
'id': 65537,
'name': 'Internal storage',
'removable': False,
'rw': True,
'volume_id': None},
{'capacity': 31436754944L,
'freespace_bytes': 29176737792L,
'freespace_objects': 1073741824L,
'id': 131073,
'name': 'SD card',
'removable': True,
'rw': True,
'volume_id': None}]

Is there any other information that I could provide to help narrow down the problem?

TIA

[kovidgoyal]

libmtp is unable to upload a file to the root of the internal storage. Either that directory is read only or the device is full or something like that or the device is locked (some firmware prevents USB connection with devices when their screen is locked).

[sgtrock]

OK, now we're getting some place. I used File Manager to check the permissions of the root directory of sdcard0 (the internal card on my tablet). It shows that the root directory owner is system, the group is sdcard_rw. Permissions are set to:

Owner: 000
Group: rwx
Others: r0x

I see two ways of proceeding. Either figure out why a USB connection to calibre is not defaulting to part of group sdcard_rw, or figure out a way to set the root directory permissions for Others to rwx.

I would really like to avoid the latter if at all possible as that is a huge security hole. Any thoughts on some way of using the first option?

Thanks again!