On Wed, Feb 01, 2012 at 12:06:10PM -0500, Alan Stern wrote: > On Wed, 1 Feb 2012, Sarah Sharp wrote: > > > > > accept the U3 transition, but immediately initiate resume signaling. > > > > The hub shall initiate a resume regardless of whether it has been > > > > enabled for remote wakeup. The hub shall not send a Function Wake > > > > Device Notification, but instead shall rely on the device to send it. > > > > > > "the device" above is ambiguous; you can simply omit the second half > > > of that sentence. > > > > > > Are you sure you don't want the hub to send a notification? It seems > > > to me that this just repeats the mistake made in the original spec: A > > > USB device changes a link state away from U3 without anyone telling the > > > host about it. What if the downstream device never does send its > > > notification? > > > > The device continues to send Function Wake notifications every > > tNotification (2.5 seconds) if it has not been accessed after it sent > > the first notification. So we will eventually see it. > > ... if the device is working properly. What if it isn't? It's a legitimate concern, since they haven't had any certified hubs to test devices under up to this point. If users do run into devices that don't send device notifications, they'll notice they don't work when they enable auto-suspend, correct? It's just like any other USB 1.1/2.0 device that doesn't properly handle device suspend or resume. However, I don't think it's a big concern for certified USB 3.0 devices up to this point because the majority of those have been mass storage devices that don't do remote wakeup. Hubs are the first USB 3.0 devices to send device notifications, as far as I know. Once those get certified I assume USB 3.0 devices will also get tested under hubs, and any that do remote wakeup will get tested for this behavior. If users end up buying non-certified USB 3.0 devices, well, then they'll just have to attach them to the roothub or not enable auto-suspend, I guess. We could have endless discussions about "what if the device is broken", but I won't be able to get the specification authors to make a major change in the hub behavior this late in the game. Sarah Sharp -- 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
