I noticed that after installing beta5 on a laptop with a usb cd/dvd drive, it would only show the first session of a retail BeOS r5 disc.
It works fine with an atapi drive.
This should probably be reported on the bugtracker.
I’m not sure how sessions are handled with USB drives, should we send SCSI commands to detect them? That’s how it works for ATAPI so I guess it would make sense here as well.
In that case this is probably another problem caused by not using the same SCSI stack for the USB mass storage driver as in other cases. But doing that is not so easy, as some USB mass storage devices are extremely restrictive in what commands they accept, and in ways that they will just crash or disconnect if you send anything else (so we can’t even cleanly fail and try another way).
I made a ticket, wasn’t sure in which category it should fit best so left it in General.
It also prevents audio CD to be played from an usb cd/dvd drive…
PulkoMandy, could usb_disk change its response depending on the device name returned by the usb device?
Everything is possible 
There is already a list of quirks depending on the usb device id, that we could extend. But I guess playing audio and multisiession CDs will require more than a few quirks