On Tue, 14 Nov 2006, David Brownell wrote: > On Monday 13 November 2006 9:15 am, Alan Stern wrote: > > On Mon, 13 Nov 2006, David Brownell wrote: > > > > > It's a *driver model* API, which is also accessible from sysfs ... to > > > support > > > per-device policies, for example the (a) workaround. The mechanism exists > > > even on kernels that don't include sysfs ... although on such systems, > > > there > > > is no way for users to do things like say "ignore the fact that this mouse > > > claims to issue wakeup events, its descriptors lie". > > > > Yes, it is separate from sysfs -- but it is _tied_ to the sysfs API. > > I can't agree. If you deconfigure sysfs, it still works. > Since it's independent like that, there's no way it's "tied".
We could carry on this argument indefinitely. Yes, the device_may_wakeup stuff does work without sysfs. But it doesn't do anything significant; it amounts to no more than device_can_wakeup(). AFAIK there's no way to change the setting of the may_wakeup flag other than via sysfs. That's what I meant by "tied". > > > No; I'm saying the driver model is used to record that the hardware > > > mechanism > > > isn't available. The fact that it's because of an implementation > > > artifact > > > (bad silicon, or board layout, etc) versus a design artifact (silicon > > > designed > > > without that feature) is immaterial ... in either case, the system can't > > > use > > > the mechanism. > > > > But the information is being recorded in the wrong spot. The correct test > > should use device_can_wakeup, not device_may_wakeup. The can_wakeup flag > > is the one which records whether or not the hardware mechanism is actually > > available. > > Go look again. "may" implies (i) can , and (ii) should. So if there's a > hardware quirk registered, (i) always fails. And in the not-uncommon case > where the device misbehavior isn't known to the kernel, userspace has the > option of making (ii) kick in (the workaround mentioned above). This is a > generic approach, it works on all wakeup-capable devices. > > So "may" is correct, and "can" is insufficient. Things work differently in uhci-hcd. I still haven't submitted the patch to add device_may_wakeup support (although it was written quite a while ago and may have been posted to linux-usb-devel; I can't remember). However even when it is added and may_wakeup is off, autostop will still function. It won't rely on interrupts or other wakeup events, though -- instead the root-hub status polling mechanism will be used. Alan Stern ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys - and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV _______________________________________________ linux-usb-devel@lists.sourceforge.net To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
