Hi, On Tue, Feb 7, 2012 at 18:38, Chris Boot <bootc@xxxxxxxxx> 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@xxxxxxxxx> 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@xxxxxxxxx Profile: http://www.google.com/profiles/julian.calaby/ .Plan: http://sites.google.com/site/juliancalaby/ -- To unsubscribe from this list: send the line "unsubscribe target-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
