Re: FICON target support

From: Hannes Reinecke <hare-l3A5Bk7waGM@public.gmane.org>
To: Christian Svensson <christian-IHD7e6/dsE0@public.gmane.org>
Cc: fcoe-devel-s9riP+hp16TNLxjTenLetw@public.gmane.org,
	Bart Van Assche <bvanassche-HInyCGIudOg@public.gmane.org>,
	linux-scsi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Subject: Re: FICON target support
Date: Fri, 31 May 2019 12:17:47 +0200	[thread overview]
Message-ID: <17f0639d-bd44-c193-af29-df539be722fe@suse.de> (raw)
In-Reply-To: <CADiuDARPit+kKtQe-UGktUuxEXRMvoq7PGVPKo9DrLRkSTwNAA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>

On 5/31/19 10:52 AM, Christian Svensson wrote:
> Hi,
> 
> On Fri, May 31, 2019 at 10:08 AM Hannes Reinecke <hare@suse.de> wrote:
>> There are easier ways for this ... I'd start with virtio-ccw and
>> implement a virtual PUNCHER there ...
> 
> The larger project scope is making FICON accessories more available
> for people as crazy as I, that is wanting to run a mainframe as a
> hobbyist, but maybe not want to buy a metric ton worth of disks or
> tape robots (a 700 kg mainframe is hard enough by itself to house).
> 
> I will take a look, but from the name of it it sounds like it will not
> help me much getting FICON targets supported.
> Maybe it will help if I ever want FICON initiator.
> 
Right.

>> Still, an uphill struggle; IBM is notorious for not giving out details
>> about the internals, and simulating a puncher is one of these things.
>> (And slightly pointless, but who am I to judge ...)
> 
> It's a low-speed peripheral that has been emulated successfully in
> Hercules, and there are some petty detailed documents around the CCWs
> for 3505 around. I figured it would
> be a good start getting a FICON user-space thing implemented, before I
> try to tackle e.g. ECKDs or tapes.
> 
Oh. Sure. You might want to ask on the s390 mailing lists, too; they
typically have a quite good idea on what's going on.
The biggest problem, however, will be to get the documentation from the
HBAs themselves.
All FC HBAs will present you with some version of cooked frames, and not
allow you to access the frames themselves. So in the end you'd have to
see to get hold of the HBA documentation itself, as you need to figure
out how to pass FICON frames into the HBA.

It might be easier when you'd be working with FCoE cards, as there you
_do_ have access to the full frame, and do whatever you like with thems.
Sadly you'd need an FCoE bridge then to hook up the mainframe.

But as you have gotten hold of an FC analyser, getting an FCoE bridge
shouldn't be too hard, too :-)

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		   Teamlead Storage & Networking
hare@suse.de			               +49 911 74053 688
SUSE LINUX GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: Felix Imendörffer, Mary Higgins, Sri Rasiah
HRB 21284 (AG Nürnberg)
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