linux-kernel - Re: [PATCH v6 4/5] device property: Constify fwnode_handle

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Message-ID: <YlcAYpZ0yB6wh1uA@smile.fi.intel.com>
Date:   Wed, 13 Apr 2022 19:54:58 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Sakari Ailus <sakari.ailus@...ux.intel.com>
Cc:     Rob Herring <robh@...nel.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        Daniel Scally <djrscally@...il.com>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Len Brown <lenb@...nel.org>
Subject: Re: [PATCH v6 4/5] device property: Constify fwnode_handle_get()

On Wed, Apr 13, 2022 at 05:35:46PM +0300, Sakari Ailus wrote:
> On Sun, Apr 10, 2022 at 05:10:23PM +0300, Andy Shevchenko wrote:
> > On Sat, Apr 9, 2022 at 2:35 AM Sakari Ailus
> > <sakari.ailus@...ux.intel.com> wrote:
> > > On Fri, Apr 08, 2022 at 09:48:43PM +0300, Andy Shevchenko wrote:
> > > > As to_of_node() suggests and the way the code in the OF and software node
> > > > back ends actually uses the fwnode handle, it may be constified. Do this
> > > > for good.
> > >
> > > How?
> > >
> > > If the fwnode is const, then the struct it contains must be presumed to be
> > > const, too.
> > 
> > Why? The idea is that we are not updating the fwnode, but the container.
> > The container may or may not be const. It's orthogonal, no?
> 
> As you wrote: may or may not. The stricter requirement, i.e. const, must be
> thus followed. I think it would be fine (after adding a comment on what is
> being done) if you *know* the container struct is not const. But that is
> not the case here.

But even with the original code one may not guarantee that. How the original
code works or prevents of using a const container against non-const fwnode
pointer?

-- 
With Best Regards,
Andy Shevchenko