linux-kernel - Re: [PATCH] PM / wakeup: Avoid dev

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Date:   Mon, 29 Jul 2019 11:06:58 +0200
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Tri Vo <trong@...roid.com>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Kalesh Singh <kaleshsingh@...gle.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Ravi Chandra Sadineni <ravisadineni@...omium.org>
Subject: Re: [PATCH] PM / wakeup: Avoid dev_name collisions in wakeup class

On Saturday, July 27, 2019 7:37:07 PM CEST Tri Vo wrote:
> On Sat, Jul 27, 2019 at 6:10 AM Rafael J. Wysocki <rafael@...nel.org> wrote:
> >
> > On Sat, Jul 27, 2019 at 3:11 AM Stephen Boyd <swboyd@...omium.org> wrote:
> > >
> > > If a device is wakeup capable and the driver calls device_wakeup_init()
> > > on it during probe and then userspace writes 'enabled' to that device's
> > > power/wakeup file in sysfs we'll try to create the same named wakeup
> > > device in sysfs. The kernel will complain about duplicate file names.
> 
> Thanks for reporting the issue, Stephen!
> > >
> > > sysfs: cannot create duplicate filename '/devices/virtual/wakeup/1-1.1'
> > > kobject_add_internal failed for 1-1.1 with -EEXIST, don't try to register things with the same name in the same directory.
> > >
> > > It may be advantageous to not write 'enabled' to the wakeup file (see
> > > wakeup_store()) from userspace for these devices because we allocate
> > > devices and register them and then throw them all away later on if the
> > > device driver has already initialized the wakeup attribute. The
> > > implementation currently tries to avoid taking locks here so it seems
> > > best to optimize that path in a separate patch.
> > >
> > > Let's rename the wakeup class devices as 'wakeupN' with an IDA that's
> > > simple enough to just return some sort of number. In addition, let's
> > > make the device registering the wakeup the parent and include a 'name'
> > > attribute in case userspace wants to figure out the type of wakeup it is
> > > (in the case of virtual wakeups) or the device associated with the
> > > wakeup. This makes it easier for userspace to go from /sys/class/wakeup
> > > to a place in the device hierarchy where the wakeup is generated from
> > > like an input device.
> > >
> > > Cc: Tri Vo <trong@...roid.com>
> > > Cc: Kalesh Singh <kaleshsingh@...gle.com>
> > > Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> > > Cc: Ravi Chandra Sadineni <ravisadineni@...omium.org>
> > > Signed-off-by: Stephen Boyd <swboyd@...omium.org>
> >
> > I'd rather change the commit that introduced this issue which is only
> > in linux-next for now.
> 
> Raphael, could you roll back my patch? I'll work with Stephen to fix it.

I'll drop it, thanks!