On Fri, 2011-12-16 at 13:36 -0800, Sarah Sharp wrote: > On Fri, Dec 16, 2011 at 09:42:41PM +0100, Sebastian Andrzej Siewior wrote: > > * Matthew Wilcox | 2011-12-16 15:31:46 [-0500]: > > > > >On Fri, Dec 16, 2011 at 09:12:36PM +0100, Sebastian Andrzej Siewior wrote: > > >> * Sebastian Andrzej Siewior | 2011-12-16 15:47:24 [+0100]: > > >> > > >> >>If you want to take a stab at redoing your patch #2 to use only one > > >> >>status URB for USB 2.0 devices, I would appreciate it. Then I can build > > >> >>the abort/reset synchronization on top of it. > > >> >Okay. > > >> > > >> Just once things started to become easy.... So while I tried to have > > >> only one status urb which I always re-submit (as Matthew/ You suggested) > > >> I run into the problem that I don't have struct scsi_device yet. So I > > >> just created a device with two luns to see if this struct happens always > > >> to be same. Ofcourse it is not. > > > > > >Can you not send one status URB per LUN (instead of one per command)? > > > > The thing is by the time a status URB completes I have only the *TAG* > > number from the device which tells to which command it belongs. Sending > > one status per LUN does not help because once a status URB with TAG 1 > > arrived I have no idea to which device/LUN it does belong. ->context > > does not help here at all. > > Oh, right, now I understand. With USB 2.0, we might have one status URB > per LUN, but they're being queued to the same endpoint ring. Since the > device can re-order the commands any way it likes, we can't rely on the > scsi_device that's stored on the urb->context to be correct. > > Ok, I think we just need to divide the tag address space equally between > devices. The devinfo can keep track of the pointers to the scsi_devices > for each LUN, and what tag range each LUN has. So if you have 255 tags > available, and two LUNs, you can give one of them tag 1 to 122, and the > other tags 123 to 254. Well, no, what you want to do is use a shared tag map at the block level. That will manage a joint tag space for N queues without your having to partition it arbitrarily. see scsi_host_find_tag() and scsi_init_shared_tag_map(). James -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
