ATAPICAM in RELENG_6 sometimes swaps drives

[Dmitry Pryanishnikov]

Hello!

  My machine (running RELENG_6) has 2 ATAPI drives attached to the second
channel of Intel ICH4 built-in ATA controller ata1 (NEC DVD-RW as a master
and AOPEN CD-RW as a slave). Of course their ATAPI devices always show up
in the fixed order:

acd0: DVDR <NEC DVD RW ND-3520A/1.04> at ata1-master UDMA33
acd1: CDRW <AOPEN CD-RW CRW5232 1.04 20031128/1.04> at ata1-slave UDMA33

However, ATAPICAM devices sometimes show in the same order:

cd0 at ata1 bus 0 target 0 lun 0
cd0: <_NEC DVD_RW ND-3520A 1.04> Removable CD-ROM SCSI-0 device
cd0: 33.000MB/s transfers
cd0: Attempt to query device size failed: NOT READY, Medium not present
cd1 at ata1 bus 0 target 1 lun 0
cd1: <AOPEN CD-RW CRW5232 1.04> Removable CD-ROM SCSI-0 device
cd1: 33.000MB/s transfers
cd1: Attempt to query device size failed: NOT READY, Medium not present

and sometimes get swapped:

cd0 at ata1 bus 0 target 1 lun 0
cd0: <AOPEN CD-RW CRW5232 1.04> Removable CD-ROM SCSI-0 device
cd0: 33.000MB/s transfers
cd0: Attempt to query device size failed: NOT READY, Medium not present
cd1 at ata1 bus 0 target 0 lun 0
cd1: <_NEC DVD_RW ND-3520A 1.04> Removable CD-ROM SCSI-0 device
cd1: 33.000MB/s transfers
cd1: Attempt to query device size failed: NOT READY, Medium not present

I consider this behaviour as being quite weird and misleading. E.g., it 
doesn't allow to set up correctly a couple of useful links from 
/etc/devfs.conf:

link     cd0    sdvdrom
link     cd1     scdrom

(sometimes scdrom points not to CD-RW, but to DVD-RW drive). What's the
reason of this weirdness, can it be fixed?

Sincerely, Dmitry
-- 
Atlantis ISP, System Administrator
e-mail:  dmitry at atlantis.dp.ua
nic-hdl: LYNX-RIPE