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SubjectRe: Archive Python DAT DDS-1 tape drive with recent Linux NCR53C8XX driver


On Fri, 4 Sep 1998, Michael Wilhelm wrote:

> I am having the exact same problems but to throw something else in is that
> one of my drives does not suport disconnect. now on my 2940uw
> controler on my pc i can turn on and off disconect on each drive.
> but on this driver for the ncr53x810 i can only turn on or off the
> disconnections for the entire chain. is there a way to turn it on on
> one device?

The ncr53c8xx driver is able to read devices set-up from the NVRAM and
will not allow disconnections for devices that have been configured for
"no disconnections".
The aic7xxx code tells me that this works the same way for adaptec
controller on Linux.

Any information that is not specific to a SCSI controller with regard
to its syntax or semantic must be settable from upper level drivers and
just made available to low-level device drivers.
It is the case of allowing/not allowing disconnections for a device when
this information is not available from some controller EEPROM.
AFAIK, the scsi.c driver does not provide this information.

A SCSI device that does not support disconnections should be either:

- Black-listed in the right place.

- Thrown away which is its right place. :-)


For now, you can try the following:

1 - Use 'ncr53c8xx=disc:no' at boot time.

2 - Execute the following commands after boot-up for _all_ devices that
are able to support DISCONNECTIONS:
(replace #target by the target SCSI ID)

echo setflag #target > /proc/scsi/ncr53c8xx/0

This will reset a user flag associated with the device that contains
the NO_DISC information.

Regards,
Gerard.

PS: from REAME.ncr53c8xx:

8.7 Set flag (no_sync)

setflag <target> <flag>

target: target number

For the moment, only one flag is available:

no_sync: not allow target to disconnect.

Do not specify any flag in order to reset the flag. For example:
- setflag 4
will reset no_sync flag for target 4, so will allow it disconnections.
- setflag all
will allow disconnection for all devices on the SCSI bus.




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