@kovidgoyal, thanks again for your help! I ran "calibre-debug -d" and the output seems to indicate my first guess, that Calibre is struggling with the read-only SETTING partition:
Code:
Looking for devices...
USBDevice(busnum=1, devnum=9, vendor_id=0x054c, product_id=0x031e, bcd=0x031a, manufacturer=Sony, product=Sony Digital Book Reader, serial=08004610011DE1F5)
Detected possible device PRS505
Devices possibly connected: SONY Device Interface,
Trying to open SONY Device Interface ...
Found device nodes: /dev/sdm None None
The mountpoint /run/media/user/SETTING/ is readonly, ignoring it
Found device nodes: /dev/sdm None None
The mountpoint /run/media/user/SETTING/ is readonly, ignoring it
failed
Opening of the following devices failed
<calibre.devices.prs505.driver.PRS505 object at 0x7f71e28c5910>
Traceback (most recent call last):
File "/usr/lib64/calibre/calibre/devices/__init__.py", line 158, in debug
dev.open(det, None)
File "/usr/lib64/calibre/calibre/devices/usbms/device.py", line 864, in open
self.open_linux()
File "/usr/lib64/calibre/calibre/devices/usbms/device.py", line 638, in open_linux
self.filter_read_only_mount_points()
File "/usr/lib64/calibre/calibre/devices/usbms/device.py", line 676, in filter_read_only_mount_points
%self.__class__.__name__)
DeviceError: Hauptspeicher von PRS505 ist schreibgeschützt. Dies passiert üblicherweise aufgrund von Fehlern im Dateisystem.
The output is correct as SETTING is readonly, but Calibre does not find the READER partition (/dev/sdj). Also manually unmounting the SETTING partition does not help as Calibre somehow forces the OS to remount the SETTING partition (I did a umount, SETTING was not mounten, ran calibre-debug -d which produced the same output as above and afterwards SETTING was mounted again).
Thanks again for your patience!