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

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Date:   Thu, 01 Aug 2019 00:42:25 +0200
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Tri Vo <trong@...roid.com>
Cc:     Stephen Boyd <swboyd@...omium.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Hridya Valsaraju <hridya@...gle.com>,
        Sandeep Patil <sspatil@...gle.com>,
        Kalesh Singh <kaleshsingh@...gle.com>,
        Ravi Chandra Sadineni <ravisadineni@...omium.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        "Cc: Android Kernel" <kernel-team@...roid.com>
Subject: Re: [PATCH v6] PM / wakeup: show wakeup sources stats in sysfs

On Thursday, August 1, 2019 12:31:16 AM CEST Tri Vo wrote:
> On Wed, Jul 31, 2019 at 3:17 PM Rafael J. Wysocki <rjw@...ysocki.net> wrote:
> >
> > On Wednesday, July 31, 2019 11:59:32 PM CEST Stephen Boyd wrote:
> > > Quoting Tri Vo (2019-07-31 14:55:14)
> > > > +/**
> > > > + * wakeup_source_sysfs_add - Add wakeup_source attributes to sysfs.
> > > > + * @parent: Device given wakeup source is associated with (or NULL if virtual).
> > > > + * @ws: Wakeup source to be added in sysfs.
> > > > + */
> > > > +int wakeup_source_sysfs_add(struct device *parent, struct wakeup_source *ws)
> > > > +{
> > > > +       struct device *dev;
> > > > +       int id;
> > > > +
> > > > +       id = ida_alloc(&wakeup_ida, GFP_KERNEL);
> >
> > So can anyone remind me why the IDA thing is needed here at all?
> 
> IDA is used to generate the directory name ("ws%d", ID) that is unique
> among wakeup_sources. That is what ends up in
> /sys/class/wakeup/ws<ID>/* path.

That's not my point (see below).

> > > > +       if (id < 0)
> > > > +               return id;
> > > > +       ws->id = id;
> > > > +
> > > > +       dev = device_create_with_groups(wakeup_class, parent, MKDEV(0, 0), ws,
> > > > +                                       wakeup_source_groups, "ws%d",
> > >
> > > I thought the name was going to still be 'wakeupN'?
> >
> > So can't we prefix the wakeup source name with something like "wakeup:" or similar here?
> 
> "ws%d" here is the name in the sysfs path rather than the name of the
> wakeup source. Wakeup source name is not altered in this patch.
> 

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);

?