Regaining DMA capability of /dev/scdX drive

[Slim Joe]

2008/10/7, Rashkae <ubuntu at tigershaunt.com>:
> Slim Joe wrote:
>> Is there a way to set the DMA on a drive that uses IDE-SCSI
>> emulation (/dev/scdX)?
>>
>> Whenever I use cdparanoia to rip a physically bad audio CD
>> (e.g. with visible scratches), my CD/DVD drive invariably
>> loses its DMA functionality. This is obvious from the slow
>> reading of any later disk (data or video) placed in the
>> drive. The system as a whole also becomes less responsive,
>> a behavior which stops when I eject the data or video DVD
>> from the drive.
>>
>> The device in question is a PATA DVD-ROM reader and
>> CD writer combo drive that maps to /dev/scd0 via SCSI
>> emulation.
>>
>> I have tried various software hacks, but none seem to
>> work. Only a reboot fixes the problem! The "hdparm" program
>> appears unable to deal with devices other than those that
>> the Linux recognizes as /dev/hd*.
>>
>> hdparm -d1 /dev/scd0
>>
>> Nor does the "echo > proc" trick work since there is no
>> scd0 equivalent of /proc/ide/*/settings!
>>
>> echo "using_dma:0" > /proc/ide/hdX/settings
>>
>> There is of course the alternate program "sdparm" but I
>> simply don't know which options to pass to it to re-enable
>> DMA on /dev/scd0 (if that is possible with this tool).
>>
>
> I'm not really sure this is supposed to be happening.
>
> Could you please put one of your damaged CD's through the ringer, then
> provide the output of dmesg?

Well my problem is really how to reset the DMA on drive
that has lost it. In other words I'm looking for the
equivalent of either "hdparm -d1 /dev/hdX" or "echo
"using_dma:1" > /proc/ide/hdX/settings" for /dev/scd0. Is
there any such command?