On Thu, Apr 21, 2011 at 6:43 AM, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: > On Wed, 20 Apr 2011, Paul Stewart wrote: > >> On Wed, Apr 20, 2011 at 2:08 PM, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: >> > On Tue, 19 Apr 2011, Paul Stewart wrote: >> > >> >> Set a flag if the interrupt URB completes with ENOENT as this >> >> occurs legitimately during system suspend. ïWhen the usbnet_bh >> >> is called after resume, test this flag and try once to resubmit >> >> the interrupt URB. >> > >> > No doubt there's a good reason for doing things this way, but it isn't >> > clear. ïWhy wait until usbnet_bh() is called after resume? ïWhy not >> > resubmit the interrupt URB _during_ usbnet_resume()? >> >> Actually, I was doing this in the bh because of feedback I had gained >> early in this process about not doing submit_urb in the resume(). > > Do you have a URL for that feedback? ÂIn general, there's no reason not > to resubmit URBs during a resume callback; lots of drivers do it. ÂBut > usbnet may have some special requirements of its own that I'm not aware > of. > >> ÂIf >> that issue doesn't exist, that makes my work a lot easier. ÂIn testing >> I found that just setting this to happen in the bh might be problematic >> due to firing too early, so this is good news. >> >> >ïThis would seem >> > to be the logical approach, seeing as how usbnet_suspend() kills the >> > interrupt URB. >> >> Aha! ÂBut you'll see from the current version of my patch that we don't >> actually ever kill the interrupt URB. ÂIt gets killed all on its own (by the >> hcd?) and handed back to us in intr_complete(). ÂThis last bit about the >> complete function being called was lost on me for a while which is why >> in a previous iteration of the patch I was trying to kill the urb in suspend(). > > Why not kill the interrupt URB while suspending? ÂIt's the proper thing > to do. ÂOtherwise you run the risk that an event might happen at just > the wrong time, causing the interrupt URB to complete normally, but > _after_ the driver has finished suspending. ÂThere's a good chance the > driver would not process the event correctly. I don't mind killing the URB. I'd want to set the halt flag as well (more on why have a flag in response to your other email). You're right that there may be a race between an interrupt URB arriving and the onset of suspend, but I really can't imagine why I can't solve that by setting the flag if a submit_urb() fails in intr_complete(). > > Alan Stern > > -- 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
