Re: [PATCH v6] PM / wakeup: show wakeup sources stats in sysfs

[Stephen Boyd <swboyd@chromium.org>]

Quoting Tri Vo (2019-08-01 12:50:25)
> On Wed, Jul 31, 2019 at 4:45 PM Stephen Boyd <swboyd@chromium.org> wrote:
> >
> > Quoting Rafael J. Wysocki (2019-07-31 16:10:38)
> > > On Thu, Aug 1, 2019 at 12:59 AM Tri Vo <trong@android.com> wrote:
> > > >
> > > > >
> > > > > So why wouldn't something like this suffice:
> > > > >
> > > > > dev = device_create_with_groups(wakeup_class, parent, MKDEV(0, 0), ws,
> > > > >                                 wakeup_source_groups, "wakeup:%s", ws->name);
> > > > >
> > > > > ?
> > > >
> > > > ws->name is inherited from the device name. IIUC device names are not
> > > > guaranteed to be unique. So if different devices with the same name
> > > > register wakeup sources, there is an error.
> > >
> > > OK
> > >
> > > So I guess the names are retained for backwards compatibility with
> > > existing user space that may be using them?
> > >
> > > That's kind of fair enough, but having two different identification
> > > schemes for wakeup sources will end up confusing.
> >
> > I understand your concern about the IDA now. Thanks for clarifying.
> >
> > How about we name the devices 'wakeupN' with the IDA when they're
> > registered with a non-NULL device pointer and then name them whatever
> > the name argument is when the device pointer is NULL. If we have this,
> > we should be able to drop the name attribute in sysfs and figure out the
> > name either by looking at the device name in /sys/class/wakeup/ if it
> > isn't 'wakeupN', or follow the symlink to the device in /sys/devices/
> > and look at the parent device name there.
> 
> This makes it difficult for userspace to query the name a wakeup
> source, as it now has to first figure out if a wakeup source is
> associated with a device or not. The criteria for that is also
> awkward, userspase has to check if directory path contains "wakeupN",
> then it's a virtual wakeup source.

I think you mean if it doesn't match wakeupN then it's a virtual wakeup
source?

> 
> IMO it's cleaner to consistently have /sys/class/wakeup/wakeupN/name
> for every wakeup source.

I don't find it awkward or difficult. Just know what the name of the
/sys/class/wakeup/ path is and then extract the name from there if it
doesn't match wakeupN, otherwise read the 'device' symlink and run it
through basename.