linux-kernel - Re: [PATCH] Revert "PM / devfreq: Modify the device name as devfreq(X) for sysfs"

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Date:   Thu, 20 Feb 2020 21:01:45 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     John Stultz <john.stultz@...aro.org>
Cc:     Orson Zhai <orson.unisoc@...il.com>,
        MyungJoo Ham <myungjoo.ham@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Chanwoo Choi <cw00.choi@...sung.com>, mingmin.ling@...soc.com,
        orsonzhai@...il.com, jingchao.ye@...soc.com,
        Linux PM list <linux-pm@...r.kernel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        stable <stable@...r.kernel.org>
Subject: Re: [PATCH] Revert "PM / devfreq: Modify the device name as
 devfreq(X) for sysfs"

On Thu, Feb 20, 2020 at 11:47:41AM -0800, John Stultz wrote:
> On Thu, Feb 20, 2020 at 11:15 AM Greg Kroah-Hartman
> <gregkh@...uxfoundation.org> wrote:
> >
> > On Fri, Feb 21, 2020 at 01:37:04AM +0800, Orson Zhai wrote:
> > > This reverts commit 4585fbcb5331fc910b7e553ad3efd0dd7b320d14.
> > >
> > > The name changing as devfreq(X) breaks some user space applications,
> > > such as Android HAL from Unisoc and Hikey [1].
> > > The device name will be changed unexpectly after every boot depending
> > > on module init sequence. It will make trouble to setup some system
> > > configuration like selinux for Android.
> > >
> > > So we'd like to revert it back to old naming rule before any better
> > > way being found.
> > >
> > > [1] https://lkml.org/lkml/2018/5/8/1042
> > >
> > > Cc: John Stultz <john.stultz@...aro.org>
> > > Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> > > Cc: stable@...r.kernel.org
> > > Signed-off-by: Orson Zhai <orson.unisoc@...il.com>
> > >
> > > ---
> > >  drivers/devfreq/devfreq.c | 4 +---
> > >  1 file changed, 1 insertion(+), 3 deletions(-)
> > >
> > > diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> > > index cceee8b..7dcf209 100644
> > > --- a/drivers/devfreq/devfreq.c
> > > +++ b/drivers/devfreq/devfreq.c
> > > @@ -738,7 +738,6 @@ struct devfreq *devfreq_add_device(struct device *dev,
> > >  {
> > >       struct devfreq *devfreq;
> > >       struct devfreq_governor *governor;
> > > -     static atomic_t devfreq_no = ATOMIC_INIT(-1);
> > >       int err = 0;
> > >
> > >       if (!dev || !profile || !governor_name) {
> > > @@ -800,8 +799,7 @@ struct devfreq *devfreq_add_device(struct device *dev,
> > >       devfreq->suspend_freq = dev_pm_opp_get_suspend_opp_freq(dev);
> > >       atomic_set(&devfreq->suspend_count, 0);
> > >
> > > -     dev_set_name(&devfreq->dev, "devfreq%d",
> > > -                             atomic_inc_return(&devfreq_no));
> > > +     dev_set_name(&devfreq->dev, "%s", dev_name(dev));
> > >       err = device_register(&devfreq->dev);
> > >       if (err) {
> > >               mutex_unlock(&devfreq->lock);
> > > --
> > > 2.7.4
> > >
> >
> > Thanks for this, I agree, this needs to get back to the way things were
> > as it seems to break too many existing systems as-is.
> >
> > I'll queue this up in my tree now, thanks.
> 
> Oof this old thing. I unfortunately didn't get back to look at the
> devfreq name node issue or the compatibility links, since the impact
> of the regression (breaking the powerHAL's interactions with the gpu)
> wasn't as big as other problems we had. While the regression was
> frustrating, my only hesitancy at this point is that its been this way
> since 4.10, so reverting the problematic patch is likely to break any
> new users since then.

4.11 :)