Re: [PATCH v2 4/5] iio: magnetometer: ak8975: Drop deprecated enums from OF table

From: Rob Herring <robh@kernel.org>
To: Jonathan Cameron <jic23@kernel.org>
Cc: "Geert Uytterhoeven" <geert@linux-m68k.org>,
	"Andy Shevchenko" <andriy.shevchenko@linux.intel.com>,
	"Biju Das" <biju.das.jz@bp.renesas.com>,
	"Lars-Peter Clausen" <lars@metafoo.de>,
	"Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>,
	"linux-iio@vger.kernel.org" <linux-iio@vger.kernel.org>,
	"Geert Uytterhoeven" <geert+renesas@glider.be>,
	"Prabhakar Mahadev Lad" <prabhakar.mahadev-lad.rj@bp.renesas.com>,
	"linux-renesas-soc@vger.kernel.org"
	<linux-renesas-soc@vger.kernel.org>,
	"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS"
	<devicetree@vger.kernel.org>
Subject: Re: [PATCH v2 4/5] iio: magnetometer: ak8975: Drop deprecated enums from OF table
Date: Fri, 6 Oct 2023 09:58:34 -0500	[thread overview]
Message-ID: <CAL_Jsq+dcabJ14w793TBneipwZUFnXuA2vvPzEq9Kr98edakBA@mail.gmail.com> (raw)
In-Reply-To: <20230828152137.2db2668d@jic23-huawei>

On Mon, Aug 28, 2023 at 9:22 AM Jonathan Cameron <jic23@kernel.org> wrote:
>
> On Fri, 18 Aug 2023 17:17:44 +0200
> Geert Uytterhoeven <geert@linux-m68k.org> wrote:
>
> > Hi Andy,
> >
> > CC devicetree
> >
> > On Fri, Aug 18, 2023 at 5:03 PM Andy Shevchenko
> > <andriy.shevchenko@linux.intel.com> wrote:
> > > On Fri, Aug 18, 2023 at 11:40:37AM +0000, Biju Das wrote:
> > > > > Subject: Re: [PATCH v2 4/5] iio: magnetometer: ak8975: Drop deprecated
> > > > > enums from OF table
> > > > >
> > > > > On Fri, Aug 18, 2023 at 08:55:59AM +0100, Biju Das wrote:
> > > > > > Drop deprecated enums from OF table as corresponding entries are
> > > > > > removed from bindings and it also saves memory.
> > > > >
> > > > > You can't do this.
> > > > >
> > > > > Only sorting by "prefixed first" criteria is possible.
> > > >
> > > > The rule applies only for fallback compatible. I checked bindings and I don't
> > > > find any fallback compatibles. All compatibles are just enums. Am I missing
> > > > anything here??
> > >
> > > Yes. As per above patch. The _whole_ world is not under your / our control.
> > > NAK to this change, sorry.
> >
> > The single user ever in the upstream kernel was fixed in commit
> > 9846210b1ec9bbaa ("ARM: tegra: seaboard: add missing DT vendor
> > prefixes") in v3.8 back in 2012.
> > And it had to be fixed again 9 years later in commit fa0fdb78cb5d4cde
> > ("ARM: dts: am335x: Use correct vendor prefix for Asahi Kasei Corp.").
> >
> > There may be other out-of-tree users, which would be broken by this
> > change.  Typically we wait a few years between deprecating a compatible
> > value and removing support from the driver.
> >
> > As Biju is only deprecating these compatible values in PATCH 3/5 of
> > his series, this may be a bit premature.
> Absolutely.  I'd go a bit further.
> Unless there is a maintenance reason to remove these (after a few years from
> removal in the binding doc) then we never remove them as it can only hurt users.

I'm tracking undocumented compatibles (with 'make
dt_compatible_check') in the kernel tree. Dropping the binding makes
these undocumented (and now showing up in my diff between Linus and
next). So please apply both or none.

Rob