Red Hat Bugzilla – Bug 78718
DMA does not work for DVD/CDROM drives with kernel-2.4.18-18.7.x.i686.rpm
Last modified: 2007-04-18 12:48:45 EDT
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Description of problem:
kernel-2.4.18-18.7.x.i686.rpm appears to be compiled with DMA enabled for disks
Version-Release number of selected component (if applicable):
Steps to Reproduce:
Run "hdparm -d 1 /dev/hdc" where /dev/hdc is a DVD/CDROM drive.
Actual Results: Hdparm has the following output
> setting using_dma to 1 (on)
> HDIO_SET_DMA failed: Operation not permitted
> using_dma = 0 (off)
Expected Results: The DVD/CDROM drive should have DMA enabled.
This problem was seen in kernel-2.4.18-17.7.x.i686.rpm and
kernel-2.4.18-18.7.x.i686.rpm (recent updates).
DMA can be enabled with kernel prior to these ones.
NOTE: As with the 8.0 release, IDE DMA on CD-ROM drives is disabled by
default. If you are sure that your CD-ROM drive is capable of IDE
DMA, place the following line in the /etc/modules.conf file:
options ide-cd dma=1
That worked. Thanks. Perhaps the 7.3 documentation needs updating?
Updating the docs is definitely a good idea.
And this extra flag in modules.conf seems a little redundant. DMA for CD drives
was already disabled by default and had to be enabled using harddiskhdx. Now
one will need to enable DMA for CD drives on 2 different places (at least on 7.x).
You are making it really hard to reenable DMA on CD drives. No need for that...