[digiKam-users] How to interpret DigiKam error message when connecting to camera

[Remco Viëtor]

On lundi 29 juin 2020 18:01:27 CEST Stuart T Rogers wrote:
> Well I have been able to recreate the message from Digikam but only by
> having the camera open in Dolphin file manager and accessing the files,
> then Digikam fails to connect.
> 
> One interesting point I have found is that if I have the camera open in
> Dolphin accessing the files then I can also open the camera in Gwenview
> at the same time but still not in Digikam. This does mean to me that
> Digikam is accessing the camera using a different method to that of some
> other applications. I have also tested Darktable and it also is unable
> to access the camera if it is open in another app like Dolphin or
> Gwenview, so it looks like Darktable uses the same method as Digikam and
> would likely exhibit the same issue on your system (it shows no
> supported devices when I try to scan for devices on import).
> 
> Also on checking how my distro manages removable devices I have it set
> to NOT auto mount anything at all!
> 
> I think the only resolution for you would be to raise this as an issue
> with your distro as it looks like Digikam is working as designed.

That would be consistent with the computer using the MTP protocol to access 
the camera. Iirc, that protocol allows only one access at the time to the file 
system on the camera, so once KDE/Plasma grabs the device, Digikam won't have 
access anymore. Same for Darktable, as neither is using the KDE libraries 
(gPhoto2 is used to access the camera). 

That also means that the distro works as designed, as the failure is inherent 
to the protocol used. 

So there are two options:
- tell the camera to behave as a mass storage device (if that's possible), 
then it can be mounted as an external drive
- use a card reader

Remco

(P.S. I told OP the same thing in his parallel thread, he chose to skip over 
the MTP bit, and just started ranting about how using a card reader was more 
complicated and bad for the SD card, he is now ignored both here and in the dt 
list)