Well, things were sorted out. Looking at that /etc/fbtab file Jonathan Gray pointed out (and yes, this is not a typo of /etc/fstab like I thought before) I can spot the /dev/drm0 in that long list of devices prepared for chown at login.
But, that file is filled in for ttyC0 only, the tty that most users are using it for login. But, giving the fact that I got some annoying kernel messages from my connecting/disconnecting USB mouse with aggresive power management routines, I was using ttyC1 for login. From that things got another way. I think this clarifies the other issue of changing tty / ownership change mentioned in this thread by somebody else. So the error was not really an error, going back to ttyC0 login I got the right permission and the messages are no more. Of course I can edit the /etc/fbtab, too. One question please: is it right that not getting access to /dev/drm0 is like losing hardware acceleration for applications using it? Thanks.
