I just bought a shiny new 16x dvd burner (box says IOMagic IDVD16DD, 
drive says Magicspin 1016IM), and can burn dvds perfectly...  just not 
read them.

Tried with both a dvd I burnt and with a purchased factory-made DVD, on 
two computers, with three different IDE controllers, with no change.

Under 2.6.8.1, trying to read files off a dvd instantly oopses.  Under 
2.6.11.7, reads are very, very slow, pegs the CPU at 100% (with dma 
on!), and sometimes give errors in the logs.  Under 2.6.12-rc3, reads 
don't work at all, 100% cpu, always logs errors, dma gets disabled, and 
typically the box takes a reboot to get it usable after trying to read 
(box is bogged down; 2 second keyboard delay, etc).  Those are using 
ide-cd; trying ide-scsi just panics.

Burning works perfectly; 8x burns use about 3% cpu, with no errors.

Motherboard in this system is a MSI 694D Pro (dual pentium 3) with Via 
VT82c686a chipset.  I use pci=noacpi, as acpi causes other problems 
(most notably two of my PCI slots stop working, even with the board 
flashed to the latest bios; putting a card in them causes either hangs 
or nobody cared errors).  Enabling acpi doesn't change the dvd problems. 
  Tested using both the standard ata/66 controller and the promise 
PDC20265 ide RAID controller.

As a test, I drove the drive over to a relative's house, and popped it 
into her dual-boot system, with a via 82c596b chipset, no acpi at all. 
under 2.6.11.7, it has the exact same symptoms as on my box.  Under 
windoze, the drive works flawlessly, and can even read the dvds I burnt 
under linux with no errors.

I don't have a copy of the oops under 2.6.8.1, however I'm guessing that 
has been fixed already, since it doesn't happen under newer kernels. 
Under .12-rc3, the following gets logged:  (ugly paste alert!)

Apr 21 19:18:57 localhost kernel: ISO 9660 Extensions: Microsoft Joliet 
Level 3
Apr 21 19:18:57 localhost kernel: ISO 9660 Extensions: RRIP_1991A
Apr 21 19:19:27 localhost kernel: hdf: command error: status=0x51 { 
DriveReady SeekComplete Error }
Apr 21 19:19:27 localhost kernel: hdf: command error: error=0x54 { 
AbortedCommand LastFailedSense=0x05 }
Apr 21 19:19:27 localhost kernel: ide: failed opcode was: unknown
Apr 21 19:19:32 localhost kernel: hdf: command error: status=0x51 { 
DriveReady SeekComplete Error }
Apr 21 19:19:32 localhost kernel: hdf: command error: error=0x54 { 
AbortedCommand LastFailedSense=0x05 }
Apr 21 19:19:32 localhost kernel: ide: failed opcode was: unknown
Apr 21 19:19:32 localhost kernel: end_request: I/O error, dev hdf, 
sector 8107876
Apr 21 19:19:32 localhost kernel: Buffer I/O error on device hdf, 
logical block 2026969
Apr 21 19:19:37 localhost kernel: hdf: command error: status=0x51 { 
DriveReady SeekComplete Error }
Apr 21 19:19:37 localhost kernel: hdf: command error: error=0x54 { 
AbortedCommand LastFailedSense=0x05 }
Apr 21 19:19:37 localhost kernel: ide: failed opcode was: unknown
Apr 21 19:19:37 localhost kernel: end_request: I/O error, dev hdf, 
sector 8107880
Apr 21 19:19:37 localhost kernel: Buffer I/O error on device hdf, 
logical block 2026970
Apr 21 19:19:43 localhost kernel: hdf: command error: status=0x51 { 
DriveReady SeekComplete Error }
Apr 21 19:19:43 localhost kernel: hdf: command error: error=0x54 { 
AbortedCommand LastFailedSense=0x05 }
Apr 21 19:19:43 localhost kernel: ide: failed opcode was: unknown
Apr 21 19:19:43 localhost kernel: end_request: I/O error, dev hdf, 
sector 8107884
Apr 21 19:19:43 localhost kernel: Buffer I/O error on device hdf, 
logical block 2026971

Or, sometimes:

Apr 21 19:21:32 localhost kernel: hdf: cdrom_decode_status: status=0x51 
{ DriveReady SeekComplete Error }
Apr 21 19:21:32 localhost kernel: hdf: cdrom_decode_status: error=0x40 { 
LastFailedSense=0x04 }
Apr 21 19:21:32 localhost kernel: ide: failed opcode was: unknown
Apr 21 19:21:39 localhost kernel: hdf: cdrom_decode_status: status=0x51 
{ DriveReady SeekComplete Error }
Apr 21 19:21:39 localhost kernel: hdf: cdrom_decode_status: error=0x40 { 
LastFailedSense=0x04 }
Apr 21 19:21:39 localhost kernel: ide: failed opcode was: unknown
Apr 21 19:21:45 localhost kernel: hdf: cdrom_decode_status: status=0x51 
{ DriveReady SeekComplete Error }
Apr 21 19:21:45 localhost kernel: hdf: cdrom_decode_status: error=0x40 { 
LastFailedSense=0x04 }
Apr 21 19:21:45 localhost kernel: ide: failed opcode was: unknown
Apr 21 19:21:52 localhost kernel: hdf: cdrom_decode_status: status=0x51 
{ DriveReady SeekComplete Error }
Apr 21 19:21:52 localhost kernel: hdf: cdrom_decode_status: error=0x40 { 
LastFailedSense=0x04 }
Apr 21 19:21:52 localhost kernel: ide: failed opcode was: unknown
Apr 21 19:21:52 localhost kernel: hdf: ide_intr: huh? expected NULL 
handler on exit
Apr 21 19:21:52 localhost kernel: hdf: ATAPI reset complete
Apr 21 19:21:59 localhost kernel: hdf: cdrom_decode_status: status=0x51 
{ DriveReady SeekComplete Error }
Apr 21 19:21:59 localhost kernel: hdf: cdrom_decode_status: error=0x40 { 
LastFailedSense=0x04 }
Apr 21 19:21:59 localhost kernel: ide: failed opcode was: unknown
Apr 21 19:22:06 localhost kernel: hdf: cdrom_decode_status: status=0x51 
{ DriveReady SeekComplete Error }
Apr 21 19:22:06 localhost kernel: hdf: cdrom_decode_status: error=0x40 { 
LastFailedSense=0x04 }
Apr 21 19:22:06 localhost kernel: ide: failed opcode was: unknown
Apr 21 19:22:13 localhost kernel: hdf: cdrom_decode_status: status=0x51 
{ DriveReady SeekComplete Error }
Apr 21 19:22:13 localhost kernel: hdf: cdrom_decode_status: error=0x40 { 
LastFailedSense=0x04 }
Apr 21 19:22:13 localhost kernel: ide: failed opcode was: unknown
Apr 21 19:22:13 localhost kernel: hdf: ide_intr: huh? expected NULL 
handler on exit
Apr 21 19:22:13 localhost kernel: hdf: ATAPI reset complete
Apr 21 19:22:13 localhost kernel: end_request: I/O error, dev hdf, 
sector 8107972
Apr 21 19:22:13 localhost kernel: Buffer I/O error on device hdf, 
logical block 2026993

Errors with "huh?" in them are always fun.  :)

In addition, I've attached the complete output of dmesg (at a fresh 
boot; attempting to read a dvd very quickly clobbers the boot 
information with the errors), in case it's helpful at all.

The errors and symptoms do not change of the DVD is ISO or UDF.

I have also observed problems reading CDs on my cd-rw drive (the other 
drive visible in the dmesg output), specifically the log entries, but 
without the other problems, and the reads always complete and go normal 
speed.  Reading a cd gives:

hdg: command error: status=0x51 { DriveReady SeekComplete Error }
hdg: command error: error=0x54 { AbortedCommand LastFailedSense=0x05 }
ide: failed opcode was: unknown
end_request: I/O error, dev hdg, sector 0
Buffer I/O error on device hdg, logical block 0
hdg: command error: status=0x51 { DriveReady SeekComplete Error }
hdg: command error: error=0x54 { AbortedCommand LastFailedSense=0x05 }
ide: failed opcode was: unknown
end_request: I/O error, dev hdg, sector 0
Buffer I/O error on device hdg, logical block 0
hdg: command error: status=0x51 { DriveReady SeekComplete Error }
hdg: command error: error=0x54 { AbortedCommand LastFailedSense=0x05 }
ide: failed opcode was: unknown
end_request: I/O error, dev hdg, sector 0
Buffer I/O error on device hdg, logical block 0
hdg: command error: status=0x51 { DriveReady SeekComplete Error }
hdg: command error: error=0x54 { AbortedCommand LastFailedSense=0x05 }
ide: failed opcode was: unknown
end_request: I/O error, dev hdg, sector 0
Buffer I/O error on device hdg, logical block 0
cdrom: hdg: mrw address space DMA selected


Any ideas?  If there's any tests/output that would help track it down, 
I'll be glad to try/post them.


Thanks in advance,
--Randy