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. Chris -- Chris Boot bootc@xxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
