I have tried the following:
- comment out the code that stalls the machine when the condition in
question is encountered.
- run dd over a couple of good blocks on the CD.
- run dd over the corrupted blocks. This leads now to very similar
errors as in the PIO case.
- reenable DMA with hdparm, because it is automatically disabled by the
ide-cd driver if an error occurs (why that? the error has nothing to
do with DMA here).
- repeat the first dd command on the good blocks and compare the
results.
The results are identical, thus I cannot verify the "4 byte shift" Alan
has been talking about. Of course this is a CD-ROM only scenario, thus
I can't tell anything about hard disks.
Is it possible that the 4-byte shift occurs only with some particular
(older?) version of the chipset?
In any case, the condition that usually causes Linux to stall is
indeed a perfectly valid condition for DMA when the device transfers
less data than it's supposed to. I doubt that hanging the system
without more detailed checks is the right measure to take there.
Martin
-- Martin Wilck Phone: +49 5251 8 15113 Fujitsu Siemens Computers Fax: +49 5251 8 20409 Heinz-Nixdorf-Ring 1 mailto:Martin.Wilck@Fujitsu-Siemens.com D-33106 Paderborn http://www.fujitsu-siemens.com/primergy
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