On Wed, Jul 31, 2019 at 1:41 AM Stephen Boyd <swb...@chromium.org> wrote: > > Quoting Rafael J. Wysocki (2019-07-30 16:05:55) > > On Wed, Jul 31, 2019 at 12:26 AM Stephen Boyd <swb...@chromium.org> wrote: > > > > > > Quoting Rafael J. Wysocki (2019-07-30 15:17:55) > > > > On Tuesday, July 30, 2019 8:48:09 PM CEST Stephen Boyd wrote: > > > > > > > > > > Using the same prefix for the class and the device name is quite > > > > > common. > > > > > For example, see the input, regulator, tty, tpm, remoteproc, hwmon, > > > > > extcon classes. I'd prefer it was left as /sys/class/wakeup/wakeupN. > > > > > The > > > > > class name could be changed to wakeup_source perhaps (i.e. > > > > > /sys/class/wakeup_source/wakeupN)? > > > > > > > > Alternatively /sys/class/wakeup/wsN > > > > > > > > > > Or /sys/class/wakeup/eventN? It's your bikeshed to paint. > > > > So actually the underlying problem here is that device_wakeup_enable() > > tries to register a wakeup source and then attach it to the device to > > avoid calling possibly sleeping functions under a spinlock. > > Agreed, that is one problem. > > > > > However, it should be possible to call wakeup_source_create(name) > > first, then attach the wakeup source to the device (after checking for > > presence), and then invoke wakeup_source_add() (after dropping the > > lock). If the wakeup source virtual device registration is done in > > wakeup_source_add(), that should avoid the problem altogether without > > having to introduce extra complexity. > > While reordering the code to do what you describe will fix this specific > duplicate name problem, it won't fix the general problem with reusing > device names from one bus on a different bus/class.
Fair enough. > We can run into the same problem when two buses name their devices the > same name and then we attempt to attach a wakeup source to those two > devices. Or we can have a problem where a virtual wakeup is made with > the same name, and again we'll try to make a duplicate named device. > Using something like 'event' or 'wakeup' or 'ws' as the prefix avoids this > problem and keeps things clean. Or suffix, like "<devname-wakeup>. But if prefixes are used by an existing convention, I would prefer "ws-" as it is concise enough and should not be confusing. > We should probably avoid letting the same virtual wakeup source be made > with the same name anyway, because userspace will be confused about what > virtual wakeup it is otherwise. I concede that using the name of the > wakeup source catches this problem without adding extra code. > > Either way, I'd like to see what you outline implemented so that we > don't need to do more work than is necessary when userspace writes to > the file. Since we agree here, let's make this change first. I can cut a patch for that in a reasonable time frame I think if no one else beats me to that. > I just don't want to see us need to change the name of the > wakeup device later on and then add a 'name' attribute to the class so > that we can avoid name collisions due to various buses controlling the > string we use to create the name of the wakeup device. OK
