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". > > > and therefore administrative > > > in nature, but now you say it's also being used to record hardware quirks. > > > > 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. > Okay. I'll write a patch to eliminate autostop and those routines when > CONFIG_PM is off. > > But that doesn't answer the question above: Should autostop check > device_can_wakeup rather than device_may_wakeup? See above, and the definition of may_wakeup(). > Also: Does the quirk/bug detection logic clear can_wakeup, as it should? > Or does it only affect may_wakeup? See above. Quirks directly recognized by the kernel clear can_wakeup. Ones that are reported via userspace clear should_wakeup. Either suffices to ensure that the may_wakeup() predicate fails. - Dave ------------------------------------------------------------------------- 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
