Use device node names rather than kernel names to check optical drives

[cconverse711]

This change allows devices to be symlinked in host for improved device naming stability

When my computer power cycles, I find that the sg device's name/path tends to change between /dev/sg0, /dev/sg1 and so forth. I've created a udev rule as follows:

# Stable symlink for the block device
SUBSYSTEM=="block", KERNEL=="sr*", ATTRS{serial}=="myserialno", ATTRS{idVendor}=="08e4", ATTRS{idProduct}=="017a", SYMLINK+="bluray/sr"

# Stable symlink for the sg device
SUBSYSTEM=="scsi_generic", ATTRS{serial}=="myserialno", ATTRS{idVendor}=="08e4", ATTRS{idProduct}=="017a", SYMLINK+="bluray/sg"

Thus I can provide the symlinks as the devices in the compose definition:

    devices:
      - "/dev/bluray/sr:/dev/bluray_sr"
      - "/dev/bluray/sg:/dev/bluray_sg"

However the existing 54-check-optical-drive.sh is incompatible with these symlinks due to its use of kernel names. This fix will allow the drives to be detected even when symlinks are used.

[jlesage]

What was the problem exactly with 54-check-optical-drive.sh ?

The change seems to break (at least in my case) usual scenario where /dev/sr* and /dev/sg* are exposed.

[cconverse711]

The problem I was finding was that 54-check-optical-drive.sh was unable to find the optical drives when I tried mapping them into the container using their symlinks. The -k flag to lsscsi prevented the symlinks from being detected by the script. But now I see with my changes, makemkvcon reports not finding usable optical drives.

It's not clear to me how makemkvcon is searching for optical drives, but I'll have to consider some workarounds. Ultimately this is so I no longer have to keep editing my docker compose file upon reboots, but perhaps there's no better option