Re: [Scst-devel] SCST NACA support

[Bart V. A. <bva...@ac...>]

On 04/07/13 10:15, Amitai Alkalay wrote:
> I'm looking for a disk support, but from what I understand I still need ACA.
> The main reason is for supporting AIX.
> For example, in case of a unit attention where the device's state have
> changed (mode settings, capacity etc..), reads/writes (that are already
> in the fc/iscsi adapter queue, or was just sent and haven't arrived yet)
> could be sent to the target with wrong settings, and a data
> loss/corruption may occur. So in case of UA, we need to abort all the
> pending commands in the queues.
> This is where NACA comes to our aid, since it would block the commands
> for us.

SCST associates a FSM (finite state machine) with each SCSI command. The 
function that drives the state transitions is scst_process_active_cmd(). 
You will have to make sure that you understand the roles of the 
different command states. ACA support can be added by inserting the 
appropriate code in the proper SCST command states. A high-level 
description of the command states can be found in 
http://scst.sourceforge.net/scst_pg.html.

Hope this helps,

Bart.