Subject: Re: select vs select with ATN (scsi bus management)
To: Eric S. Hvozda <>
From: Eduardo E. Horvath <>
List: tech-kern
Date: 09/14/1995 09:11:13
On Thu, 14 Sep 1995, Eric S. Hvozda wrote:

> This is kinda of topic, but since the question developed while writing 
> my scsi driver, we'll try it here...
> Apparently the FAS408 and ESP406 can do select, select with ATN, and 
> select with ATN and stop.
> select selects a target; this I know.  So what's the difference between
> select and select with ATN?  Why would I want to do one over the other?
> Ideas?

Select is used by SCSI I implementations which connect to a device and 
then send the SCSI command.

Select with ATN is mandated by SCSI II and should cause the target to 
perform a message out phase.  The initiator should then send an IDENTIFY 
message followed by any other messages it wants to send.

I suggest you use select-with-ATN and send out a proper IDENTIFY 
message.  This allows your driver to select the proper LUN it wants to 
talk to, since the LUN does not seem to be provided properly in the 
command with the current mid-level SCSI drivers.