Quoting Rafael J. Wysocki (2019-08-16 05:17:23) > On Wed, Aug 14, 2019 at 8:37 PM Tri Vo <tr...@android.com> wrote: > > > > On Wed, Aug 14, 2019 at 1:40 AM Tony Lindgren <t...@atomide.com> wrote: > > > > > > * Stephen Boyd <swb...@chromium.org> [691231 23:00]: > > > > I also notice that device_set_wakeup_capable() has a check to see if the > > > > device is registered yet and it skips creating sysfs entries for the > > > > device if it isn't created in sysfs yet. Why? Just so it can be called > > > > before the device is created? I guess the same logic is handled by > > > > dpm_sysfs_add() if the device is registered after calling > > > > device_set_wakeup_*(). > > > > > > Hmm just guessing.. It's maybe because drivers can enable and disable > > > the wakeup capability at any point for example like driver/net drivers > > > do based on WOL etc? > > > > > > > There's two approaches I see: > > > > > > > > 1) Do a similar check for device_set_wakeup_enable() and skip > > > > adding the wakeup class until dpm_sysfs_add(). > > > > > > > > 2) Find each case where this happens and only call wakeup APIs > > > > on the device after the device is added. > > > > > > > > I guess it's better to let devices have wakeup modified on them before > > > > they're registered with the device core? > > > > > > I think we should at least initially handle case #1 above as multiple > > > places otherwise seem to break. Then maybe we could add a warning to > > > help fix all the #2 cases if needed? > > > > Makes sense. For case#1, we could also just register the wakeup source > > without specifying the parent device if the latter hasn't been > > registered yet. Userspace won't be able to associate a wakeup source > > to the parent device. But I think it's a reasonable fix, assuming we > > want to fix devices not being added before calling wakeup APIs #2. > > Well, OK > > I'm going to drop the entire series from linux-next at this point and > let's start over.
I was going to send the first patch I floated as a more formal patch to be applied to the PM tree. I was waiting to see if the semantics of device_set_wakeup_*() could be clarified because I don't understand if they're allowed to be called before device_add(). > > Also note that all of this is not an issue until we start to add > children under the device passed to device_set_wakeup_enable() and > friends so maybe that is not a good idea after all? My primary goal is to know what wakeup is associated with a device. If we delay creation of the sysfs node to the time that device_add() is called then it will allow device_set_wakeup_enable() to be called before the device is published to userspace. Is anything wrong with that? This seems to be the intention of the API based on the way device_set_wakeup_capable() is written. Furthermore, if we make this change then we don't need to fix various drivers to reorder calls to device_set_wakeup_enable() and device_add(), so it looks like the right approach. I'll send the patch over the list now and let you decide. I'll also send a patch for serio to have it operate on the device in a less racy way, but not necessarily after the device_add() is called.