linux-kernel - Re: [PATCH 1/6] software node: Provide replacement for device_add

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Date:   Wed, 3 Feb 2021 16:51:18 +0200
From:   Heikki Krogerus <heikki.krogerus@...ux.intel.com>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Felipe Balbi <balbi@...nel.org>,
        Mathias Nyman <mathias.nyman@...el.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "open list:ULTRA-WIDEBAND (UWB) SUBSYSTEM:" 
        <linux-usb@...r.kernel.org>
Subject: Re: [PATCH 1/6] software node: Provide replacement for
 device_add_properties()

On Wed, Feb 03, 2021 at 03:39:02PM +0100, Rafael J. Wysocki wrote:
> On Wed, Feb 3, 2021 at 3:27 PM Heikki Krogerus
> <heikki.krogerus@...ux.intel.com> wrote:
> >
> > On Wed, Feb 03, 2021 at 02:50:24PM +0100, Rafael J. Wysocki wrote:
> > > On Wed, Feb 3, 2021 at 10:45 AM Heikki Krogerus
> > > <heikki.krogerus@...ux.intel.com> wrote:
> > > >
> > > > On Tue, Feb 02, 2021 at 05:08:40PM +0100, Rafael J. Wysocki wrote:
> > > > > It looks like there is a use case that cannot be addressed by using
> > > > > device_add_properties() and that's why you need this new function.
> > > > >
> > > > > Can you describe that use case, please, and explain what the problem
> > > > > with using device_add_properties() in it is?
> > > >
> > > > The problem with device_add_properties() is that it gives false
> > > > impression that the device properties are somehow directly attached to
> > > > the devices, which is not true. Now, that should not be a major issue,
> > > > but it seems that it is. I think Lee Jones basically used that as an
> > > > argument to refuse changes (and pretty minor changes) that would have
> > > > allowed us to use software nodes with the MFD drivers.
> > > >
> > > > Nevertheless, I was not planning to provide a replacement for it
> > > > originally. We do in any case have the real issue caused by that
> > > > device_remove_properties() call in device_del() which has to be fixed.
> > >
> > > What's that issue, specifically?
> >
> > The problem is that we can't now reuse or share if necessary, or just
> > in general be in charge of the lifetime of the software nodes because
> > that call is in device_del(). Now the lifetime of the software nodes
> > is always tied to the devices they are attached, no questions asked.
> 
> I see and so instead you want the reference counting to trigger the
> cleanup when the count gets to 0.
> 
> Sounds reasonable to me and please put this information into the patch
> changelog.

Yes. I'll do that.

thanks,

-- 
heikki