From: Julian Calaby <julian.calaby@gmail.com>
To: Chris Boot <bootc@bootc.net>
Cc: Stefan Richter <stefanr@s5r6.in-berlin.de>,
Clemens Ladisch <clemens@ladisch.de>,
target-devel@vger.kernel.org,
linux1394-devel@lists.sourceforge.net,
Boaz Harrosh <bharrosh@panasas.com>,
Andy Grover <agrover@redhat.com>,
linux-scsi@vger.kernel.org, lkml <linux-kernel@vger.kernel.org>
Subject: Re: FireWire/SBP2 Target mode
Date: Tue, 7 Feb 2012 21:06:57 +1100 [thread overview]
Message-ID: <CAGRGNgXj37g6Q5W+hwkBjQHh3a8to+2Vq5Yx_omC8p9bdZrdBw@mail.gmail.com> (raw)
In-Reply-To: <4F30D4F6.1040802@bootc.net>
Hi,
On Tue, Feb 7, 2012 at 18:38, Chris Boot <bootc@bootc.net> wrote:
> On 06/02/2012 23:09, Chris Boot wrote:
>>
>>
>> On 6 Feb 2012, at 23:00, Julian Calaby wrote:
>>
>>> Hi,
>>>
>>> On Tue, Feb 7, 2012 at 09:28, Chris Boot<bootc@bootc.net> wrote:
>>>>
>>>> On 6 Feb 2012, at 20:26, Stefan Richter wrote:
>>>>
>>>>> On Feb 06 Chris Boot wrote:
>>>>>>
>>>>>> On 06/02/2012 14:43, Clemens Ladisch wrote:
>>>>>>>
>>>>>>> Chris Boot wrote:
>>>>>>>>
>>>>>>>> You can pull the code from:
>>>>>>>> git://github.com/bootc/Linux-SBP-2-Target.git
>>>>>>>
>>>>>>>
>>>>>>> The TODO file says:
>>>>>>>>
>>>>>>>> * Update Juju so we can get the speed in the fw_address_handler
>>>>>>>> callback
>>>>>>>
>>>>>>>
>>>>>>> What is the speed needed for?
>>>>>>
>>>>>>
>>>>>> "The speed at which the block write request to the MANAGEMENT_AGENT
>>>>>> register is received shall determine the speed used by the target for
>>>>>> all subsequent requests to read the initiator’s configuration ROM,
>>>>>> fetch
>>>>>> ORB’s from initiator memory or store status at the initiator’s
>>>>>> status_FIFO. Command block ORB’s separately specify the speed for
>>>>>> requests addressed to the data buffer or page table."
>>>>>>
>>>>>> (T10/1155D Revision 4 page 53/54)
>>>>>
>>>>>
>>>>> I guess it is not too hard to add this to the AR-req handler. On the
>>>>> other hand, I see little reason to follow the SBP-2 spec to the letter
>>>>> here. The target driver could just use the maximum speed that the core
>>>>> figured out. On the other hand, this requires of course
>>>>> - the target to wait for core to finish scanning an initiator,
>>>>> - the core to offer an API to look up an fw_device by a
>>>>> card--generation--nodeID tuple.
>>>>>
>>>>> The intention of the spec is IMO clearly to enable target
>>>>> implementations
>>>>> that do not need to implement topology scanning. I have a hard time to
>>>>> think of a valid scenario where an initiator needs to be able to steer
>>>>> a
>>>>> target towards a lower wire speed than what the participating links and
>>>>> PHYs actually support.
>>>>
>>>>
>>>> The only thing stopping me from getting the speed is the fact that
>>>> struct fw_request is opaque. The value is easily available from
>>>> request->response.speed and I kind of do that already in a very hackish way.
>>>> I've sent a separate patch which adds a function that can be used to access
>>>> that one value.
>>>>
>>>> Waiting until the bus scan is complete isn't actually that great as I
>>>> see the first LOGIN requests often before the fw_node is seen at all. I'd
>>>> have to turn away the requester and hope they try again. I'm fairly sure my
>>>> little tweak in my patch is a simple enough solution.
>>>
>>>
>>> Stupid question: Could you use a completion queue or something
>>> equivalent to wait until you have seen the fw_node, *then* process the
>>> LOGIN request?
>>
>>
>> The fw_address_handler callback is called in interrupt context, and I
>> can't sleep from within there. As far as I'm aware I must call
>> fw_send_response() from within the callback and can't defer that until I've
>> scheduled something on a work queue. Please correct me if I'm wrong though,
>> as that might be useful anyway.
>
>
> Hmm sorry I've thought about this overnight and clearly I was talking
> rubbish. Yes, I need to reply in the fw_address_handler but all I tend to do
> in there is schedule a task to the the main part of the work anyway. As most
> of the operations require fetching an ORB from the initiator I have to do
> this from user context.
>
> So it's possible I could do this by waiting in my scheduled work function
> until the fw_node is available and get the speed from that - but that seems
> like an inordinate amount of work when I can follow the standard and do it
> really easily by pulling it out of the fw_request.
Fair enough, I assumed that there might have been some reason why you
wouldn't have it at that point, not just convention getting in the
way.
Thanks,
--
Julian Calaby
Email: julian.calaby@gmail.com
Profile: http://www.google.com/profiles/julian.calaby/
.Plan: http://sites.google.com/site/juliancalaby/
next prev parent reply other threads:[~2012-02-07 10:07 UTC|newest]
Thread overview: 100+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-08-17 14:51 FireWire/SBP2 Target mode Chris Boot
2011-08-17 18:57 ` Stefan Richter
2011-08-18 16:19 ` Clemens Ladisch
2012-02-01 19:50 ` Andy Grover
2012-02-01 21:41 ` Stefan Richter
2012-02-02 9:22 ` Boaz Harrosh
2012-02-02 10:09 ` Clemens Ladisch
2012-02-06 13:13 ` Chris Boot
2012-02-06 14:43 ` Clemens Ladisch
2012-02-06 14:51 ` Chris Boot
2012-02-06 20:26 ` Stefan Richter
2012-02-06 22:28 ` Chris Boot
2012-02-06 23:00 ` Julian Calaby
2012-02-06 23:09 ` Chris Boot
2012-02-07 7:38 ` Chris Boot
2012-02-07 10:06 ` Julian Calaby [this message]
2012-02-07 19:17 ` Stefan Richter
2012-02-07 19:53 ` Chris Boot
2012-02-11 19:43 ` [RFC][PATCH 00/13] firewire-sbp-target: FireWire SBP-2 SCSI target Chris Boot
2012-02-11 19:44 ` [PATCH 01/13] firewire: Add function to get speed from opaque struct fw_request Chris Boot
2012-02-11 19:44 ` [PATCH 02/13] firewire: Add EXPORT_SYMBOL_GPL(fw_card_release) Chris Boot
2012-02-11 19:44 ` [PATCH 03/13] firewire-sbp-target: Add Kconfig, Makefile and TODO Chris Boot
2012-02-13 12:50 ` Nicholas A. Bellinger
2012-02-11 19:44 ` [PATCH 04/13] firewire-sbp-target: Add sbp_base.h header Chris Boot
2012-02-11 19:44 ` [PATCH 05/13] firewire-sbp-target: Add sbp_configfs.c Chris Boot
2012-02-11 19:44 ` [PATCH 06/13] firewire-sbp-target: Add sbp_fabric.{c,h} Chris Boot
2012-02-13 13:06 ` Nicholas A. Bellinger
[not found] ` <337FFBD7-6B4A-41CA-BB57-6038C935B5BF@bootc.net>
2012-02-13 19:53 ` Stefan Richter
2012-02-13 22:41 ` Nicholas A. Bellinger
2012-02-11 19:44 ` [PATCH 07/13] firewire-sbp-target: Add sbp_proto.{c,h} Chris Boot
2012-02-11 19:44 ` [PATCH 08/13] firewire-sbp-target: add sbp_management_agent.{c,h} Chris Boot
2012-02-11 19:44 ` [PATCH 09/13] firewire-sbp-target: Add sbp_login.{c,h} Chris Boot
2012-02-11 19:44 ` [PATCH 10/13] firewire-sbp-target: Add sbp_target_agent.{c,h} Chris Boot
2012-02-11 19:44 ` [PATCH 11/13] firewire-sbp-target: Add sbp_scsi_cmnd.{c,h} Chris Boot
2012-02-11 19:44 ` [PATCH 12/13] firewire-sbp-target: Add sbp_util.{c,h} Chris Boot
2012-02-11 19:44 ` [PATCH 13/13] firewire-sbp-target: Add to target Kconfig and Makefile Chris Boot
2012-02-12 14:12 ` [RFC][PATCH 00/13] firewire-sbp-target: FireWire SBP-2 SCSI target Stefan Richter
2012-02-12 15:13 ` Chris Boot
2012-02-12 16:16 ` Stefan Richter
2012-02-15 14:47 ` [PATCH v2 00/11] " Chris Boot
2012-02-15 14:47 ` [PATCH v2 01/11] firewire: Add function to get speed from opaque struct fw_request Chris Boot
2012-02-15 19:09 ` Stefan Richter
2012-02-15 19:10 ` Chris Boot
2012-02-15 22:01 ` Stefan Richter
2012-02-16 9:12 ` Chris Boot
2012-02-15 14:47 ` [PATCH v2 02/11] firewire: Move fw_card kref functions into linux/firewire.h Chris Boot
2012-02-15 19:10 ` Stefan Richter
2012-02-16 9:18 ` Chris Boot
2012-02-15 14:47 ` [PATCH v2 03/11] firewire-sbp-target: Add Kconfig, Makefile and TODO Chris Boot
2012-02-15 14:47 ` [PATCH v2 04/11] firewire-sbp-target: Add sbp_base.h header Chris Boot
2012-02-15 19:15 ` Stefan Richter
2012-02-16 9:55 ` Chris Boot
2012-02-15 14:47 ` [PATCH v2 05/11] firewire-sbp-target: Add sbp_configfs.c Chris Boot
2012-02-15 19:21 ` Stefan Richter
2012-02-16 9:57 ` Chris Boot
2012-02-16 13:48 ` Stefan Richter
2012-02-15 14:47 ` [PATCH v2 06/11] firewire-sbp-target: Add sbp_fabric.{c,h} Chris Boot
2012-02-15 14:47 ` [PATCH v2 07/11] firewire-sbp-target: add sbp_management_agent.{c,h} Chris Boot
2012-02-15 19:48 ` Stefan Richter
2012-02-16 10:28 ` Chris Boot
2012-02-16 14:12 ` Stefan Richter
2012-02-15 14:47 ` [PATCH v2 08/11] firewire-sbp-target: Add sbp_login.{c,h} Chris Boot
2012-02-15 21:00 ` Stefan Richter
2012-02-16 11:21 ` Chris Boot
2012-03-03 17:37 ` Stefan Richter
2012-03-15 17:48 ` Paul E. McKenney
2012-02-15 14:47 ` [PATCH v2 09/11] firewire-sbp-target: Add sbp_target_agent.{c,h} Chris Boot
2012-02-15 21:27 ` Stefan Richter
2012-02-16 11:25 ` Chris Boot
2012-02-18 14:59 ` Stefan Richter
2012-02-18 15:05 ` Chris Boot
2012-02-15 14:47 ` [PATCH v2 10/11] firewire-sbp-target: Add sbp_scsi_cmnd.{c,h} Chris Boot
2012-02-15 14:47 ` [PATCH v2 11/11] firewire-sbp-target: Add to target Kconfig and Makefile Chris Boot
2012-04-11 14:20 ` [PATCH v3 00/11] firewire-sbp-target: FireWire SBP-2 SCSI target Chris Boot
2012-04-11 14:20 ` [PATCH 01/11] firewire: Add function to get speed from opaque struct fw_request Chris Boot
2012-04-11 14:20 ` [PATCH 02/11] firewire: Move fw_card kref functions into linux/firewire.h Chris Boot
2012-04-11 14:20 ` [PATCH 03/11] firewire-sbp-target: Add Kconfig, Makefile and TODO Chris Boot
2012-04-11 14:20 ` [PATCH 04/11] firewire-sbp-target: Add sbp_base.h header Chris Boot
2012-04-11 14:20 ` [PATCH 05/11] firewire-sbp-target: Add sbp_configfs.c Chris Boot
2012-04-11 14:20 ` [PATCH 06/11] firewire-sbp-target: Add sbp_fabric.{c,h} Chris Boot
2012-04-11 14:20 ` [PATCH 07/11] firewire-sbp-target: Add sbp_management_agent.{c,h} Chris Boot
2012-04-11 14:20 ` [PATCH 08/11] firewire-sbp-target: Add sbp_login.{c,h} Chris Boot
2012-04-14 10:17 ` Stefan Richter
2012-04-11 14:20 ` [PATCH 09/11] firewire-sbp-target: Add sbp_target_agent.{c,h} Chris Boot
2012-04-14 10:49 ` Stefan Richter
2012-04-14 11:33 ` Stefan Richter
2012-04-11 14:20 ` [PATCH 10/11] firewire-sbp-target: Add sbp_scsi_cmnd.{c,h} Chris Boot
2012-04-11 14:20 ` [PATCH 11/11] firewire-sbp-target: Add to target Kconfig and Makefile Chris Boot
2012-04-12 21:02 ` [PATCH v3 00/11] firewire-sbp-target: FireWire SBP-2 SCSI target Andy Grover
2012-04-13 3:03 ` Nicholas A. Bellinger
2012-04-13 13:16 ` Chris Boot
2012-04-14 1:23 ` Nicholas A. Bellinger
2012-04-14 9:12 ` [PATCH 0/2] sbp-target: cleanup after merge into single file Chris Boot
2012-04-14 9:12 ` [PATCH 1/2] sbp-target: minor cleanups after merging " Chris Boot
2012-04-14 9:12 ` [PATCH 2/2] sbp-target: update TODO file Chris Boot
2012-04-14 21:44 ` [PATCH 0/2] sbp-target: cleanup after merge into single file Nicholas A. Bellinger
2012-04-14 23:11 ` Stefan Richter
2012-04-15 1:22 ` Nicholas A. Bellinger
2012-04-17 10:48 ` [PATCH v3 00/11] firewire-sbp-target: FireWire SBP-2 SCSI target Chris Boot
2012-04-18 7:17 ` Nicholas A. Bellinger
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