Re: [Scst-devel] scst_user - How to post Unit Attention?

[Rob T. <ro...@rt...>]

Well, some good news I suppose. I have made some minor changes to 
scst_lib and scst_user as suggested, and I can now post Unit Attentions 
which arrive at all initiators. Below is the output of a quick-and-dirty 
SCSI Ping tool that I wrote for Linux and Windows, running side by side. 
Linux is initiator via scst_local, Windows via iSCSI. Status = host, 
ASC, ASCQ, Sensekey. [val] is number of seconds that status stayed the 
same. You can see the single Unit Attentions 02280006H posted when I 
insert a virtual tape.

Z:\pingSCSI>win32\pingdev.exe \\.\Tape0
Pingdev V1.01 - Copyright (c) 2017, Rob Turk. All Rights Reserved
This beta version built by Rob Turk - The Netherlands on Dec  4 2018, 
22:20:26

Status = 02290006H [1]
Status = 023a0002H [12]
Status = 02280006H [1]
Status = 01000000H [5]
Status = 023a0002H [9]
Status = 02280006H [1]
Status = 01000000H [22]
Status = 023a0002H [5]
Status = 02280006H [1]
Status = 01000000H [19]

[root@vmscsi scst-3.3.0]# /projects/pingSCSI/Linux64/pingdev /dev/st0
Pingdev V1.01 - Copyright (c) 2017, Rob Turk. All Rights Reserved
This beta version built by Rob Turk - The Netherlands on Dec  4 2018, 
22:06:42

Status = 023a0002H [5]
Status = 02280006H [1]
Status = 01000000H [5]
Status = 023a0002H [9]
Status = 02280006H [1]
Status = 01000000H [22]
Status = 023a0002H [5]
Status = 02280006H [1]
Status = 01000000H [18]

I used a clean scst-3.3.0 tarball as start, now I need to figure out how 
to create something you can pull, but the mechanism seems to work well.

Rob

On 12/4/2018 10:22 AM, Rob Turk wrote:
> On 12/4/2018 6:15 AM, Bart Van Assche wrote:
>> On 12/2/18 2:17 AM, Rob Turk wrote:
>>> After studying file_io and the scst source code (on trunk 7800 right 
>>> now), I have not been able to figure out how to properly set a Unit 
>>> Attention condition through scst_user that registers for all 
>>> initiators. Does such a mechanism exist at all?
>>>
>>> When starting the target emulation, scst itself appears to post a 
>>> Unit Attention (Power on Reset) for every initiator. I also found 
>>> code in scst_lib.c that does this for all initiators when a Device 
>>> Reset or LUN change event occurs. How can I post my own Unit 
>>> Attention through this mechanism?
>>>
>>> Example: My target emulation is a Tape device. When empty, all 
>>> initiators poll the device (usually Test Unit Ready) and get a Not 
>>> Ready sense back. When I insert a virtual tape, the first Test Unit 
>>> Ready for each initiator should get a Unit Attention, ASC 0x28, ASCQ 
>>> 0x00 (Not ready to ready transition, medium may have changed). Does 
>>> my emulation need to keep track of this for each initiator, or is 
>>> there a way to post the Unit Attention so scst will take care of it?
>>
>> Hi Rob,
>>
>> How about the following:
>> - Below scst_capacity_data_changed(), add a new function that accepts
>>   struct scst_device *dev, int key, int asc, int ascq as arguments and
>>   that calls scst_gen_aen_or_ua() for all tgt_devs associated with
>>   'dev'.
>> - In scst_user, have a look at how SCST_USER_DEVICE_CAPACITY_CHANGED has
>>   been implemented and add a new scst_user command that triggers a call
>>   to the new function in scst_lib.
>>
>> If you post the resulting patch on the scst-devel mailing list I will 
>> have a look at it.
>>
>> Bart.
>>
>
> Hi Bart,
> Not sure if I'm up to the task, but willing to try.
>
> Rather than introducing a new scst_user command, I'd suggest adding a 
> check in dev_user_process_reply_exec() in the section that handles 
> sense data, and call the new library function if sense key equals UA. 
> That way no changes to scst_user API needs to happen, and posting of 
> UA is automatic for all emulations. Your thoughts?
>
> Rob
>
>
>
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