Re: [PATCH v2 1/5] device property: Keep dev_fwnode() and dev_fwnode_const() separate

From: Sakari Ailus <sakari.ailus@linux.intel.com>
To: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
	Heikki Krogerus <heikki.krogerus@linux.intel.com>,
	Bjorn Andersson <andersson@kernel.org>,
	Prashant Malani <pmalani@chromium.org>,
	linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-usb@vger.kernel.org, Daniel Scally <djrscally@gmail.com>
Subject: Re: [PATCH v2 1/5] device property: Keep dev_fwnode() and dev_fwnode_const() separate
Date: Mon, 3 Oct 2022 12:00:57 +0000	[thread overview]
Message-ID: <YzrO+ZNmpKetdIPU@paasikivi.fi.intel.com> (raw)
In-Reply-To: <CAJZ5v0hHPjSN-369pagN3Mnxd1yvc6+4YGb0Kpx3=+aahV=AmQ@mail.gmail.com>

Hi Rafael,

On Mon, Oct 03, 2022 at 01:54:37PM +0200, Rafael J. Wysocki wrote:
> > I ask as I just went through a large refactoring of the kobject layer to
> > mark many things const * and I find it a bit "sad" that functions like
> > this:
> >         static inline struct device *kobj_to_dev(const struct kobject *kobj)
> >         {
> >                 return container_of(kobj, struct device, kobj);
> >         }
> > have the ability to take a read-only pointer and spit out a writable one
> > thanks to the pointer math in container_of() with no one being the
> > wiser.
> 
> Well, is this really a problem?
> 
> After all, if an immutable structure is embedded in another one, that
> doesn't automatically imply that the containing structure has to be
> immutable too.  Hence, a const pointer to the inner structure doesn't
> automatically yield a const pointer to the outer one.

I think in that case it'd be better, to at least make an informed decision
on that instead of just dropping the const qualifier.

-- 
Regards,

Sakari Ailus