Unable to change sata NCQ depth due to readonly /sys/block/sdc/device/queue_depth file

[Roy Franz]

Hi,

 I am unable to change the NCQ settings for a sata drive that
supports it - NCQ is always on.  This is due to the sysfs queue_depth
file being read-only.  This is on
vanilla 2.6.21.5 running with Debian Etch.  (Several earlier versions
of the kernel
had this same issue.)  The drive (WD Raptor) is hooked up to a Nvidia
sata controller.

amd64:/# ls -al /sys/block/sdc/device/queue_depth
-r--r--r-- 1 root root 4096 2007-06-28 10:04 /sys/block/sdc/device/queue_depth
amd64:/# cat /sys/block/sdc/device/queue_depth
31
amd64:/#

I searched but did not find any helpful information on this.  Forcing
a change by changing permissions on the file did not work.

Thanks,
Roy
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