[ltp] UltraSlimBay swapping on ThinkPad 600

[Thomas Hood]

Well, after leaving this issue alone for about a year,
I just tried again to swap between floppy and CD-ROM
UltraSlimBay drives on my ThinkPad 600.

What I CAN do is:
  COLD boot with the floppy drive in the bay
  optionally: mount and unmount a floppy disk
  suspend
  remove floppy drive
  insert CD-ROM drive
  resume
  hdparm -R 0x170 0 0 /dev/hda
  optionally: mount and unmount a CD-ROM disk
  suspend
  remove CD-ROM drive
  resume
  optionally: mount and unmount a floppy disk
etc.

Note that the system must be COLD booted with the
FLOPPY drive in the bay.  Otherwise the floppy drive
will never work.

I assume that it is an exceelent idea never to remove
any drive when the disk in that drive is mounted.

Note that this procedure involves the use of "hdparm -R"
once and only once.  After removing the CD-ROM drive
I do NOT unregister its IDE interface.  Repeatedly
registering and unregistering the secondary IDE interface
eventually causes hardware faults on the primary
interface, resulting in a crash and filesystem corruption.
When I tried it, the third attempt to register trashed
ide0.

Unfortunately, not unregistering the secondary IDE
interface leaves Linux with the impression that there
is a drive there even when there isn't.  As a result,
one is liable to get access errors on /dev/cdrom.  I have
received such errors at shutdown time, but I expect they
may occur if programs try to check the CD-ROM drive for
one reason or another.  It MIGHT be okay to unregister
the secondary IDE interface once and only once
(hdparm -U 1 /dev/hda) prior to shutdown in order to
prevent error messages at that time, but I haven't
experimented with that yet and I wouldn't be surprised
if one ended up with filesystem corruption.

I believe that the 600E and later models are better 
able to handle baydrive-swapping.

--
Thomas Hood

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