I've run into an error stemming from lacking permissions when using the CDIO library to issue an eject command to my USB CD-ROM drive. I always get an error message like this:

INFO: ioctl CDROM_SEND_PACKET for command PREVENT ALLOW MEDIUM REMOVAL (0x1e) failed: Operation not permitted

The ioctl call is part of the cdda-player app I call as follows:

cdda-player -ev /dev/sr0

After taking a look into the sourcecode of libcdio, I found out that this line of code makes trouble:

int i_rc = ioctl (p_env->gen.fd, CDROM_SEND_PACKET, &cgc);

When I run the code as root (using sudo), everything works fine. Here are the permissions for my CD-ROM drive:

pi@autoradio:/import/valen/autoradio/libcdio-master $ ls -al /dev/sr0 
brw-rw----+ 1 root cdrom 11, 0 Jul  5 22:42 /dev/sr0

pi@autoradio:/import/valen/autoradio/libcdio-master $ ls -al /dev/sg0 
crw-rw----+ 1 root cdrom 21, 0 Jul  5 22:38 /dev/sg0

pi@autoradio:~ $ getfacl /dev/sr0 
getfacl: Removing leading '/' from absolute path names 
# file: dev/sr0 
# owner: root 
# group: cdrom 

The user pi is part of the cdrom group. The standard eject utility does work, though.

Now: Which permissions do I have to set for the eject operation to work as an ordinary user? Thank you.

UPDATE: Here is my kernel version:

pi@autoradio:/import/valen/autoradio/libcdio-master $ uname -a 
Linux autoradio 4.9.35-v7+ #1014 SMP Fri Jun 30 14:47:43 BST 2017 armv7l GNU/Linux 

OK, after a hint from one of the maintainers of libcdio, I found out that the version I installed was out of date and contained a bug based on improper use of O_RDWR vs. O_RDONLY. After the update, suddenly everything works fine. Nevertheless thank you for your hints!

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