Re: FireWire/SBP2 Target mode

From: Chris Boot
Date: Tue Feb 07 2012 - 14:53:23 EST

On 07/02/2012 19:17, Stefan Richter wrote:
On Feb 07 Chris Boot wrote:
On 06/02/2012 23:09, Chris Boot wrote:
On 6 Feb 2012, at 23:00, Julian Calaby wrote:
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.

Technically there are two things to perform:

1. Finish the inbound IEEE 1394 transaction to the management agent
register by means of fw_send_response(). As far as I can tell, you
don't have to do that in the address_callback(). But there is little
reason not to.

fw_send_response() ends the lifetime of an fw_request, so read the
speed code before you respond.

2. Finish the inbound SBP-2 transaction; here the login. This and
everything that leads up to it is definitely easiest to implement in
a process context, e.g. workqueue item.

Yep I do exactly that - I save the speed then schedule_work() inside the address callback, then call fw_send_response() still within the callback. The work callback uses fw_run_transaction() to fetch the ORB and deal with it.


Chris Boot
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