Re: [PATCH v2 1/4] dt-bindings: bluetooth: add new wcn3991 compatible to fix bd_addr

From: Johan Hovold <johan@kernel.org>
To: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Cc: Johan Hovold <johan+linaro@kernel.org>,
	Marcel Holtmann <marcel@holtmann.org>,
	Luiz Augusto von Dentz <luiz.dentz@gmail.com>,
	Rob Herring <robh+dt@kernel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
	Conor Dooley <conor+dt@kernel.org>,
	Johan Hedberg <johan.hedberg@gmail.com>,
	Matthias Kaehlcke <mka@chromium.org>,
	Doug Anderson <dianders@google.com>,
	Bjorn Andersson <quic_bjorande@quicinc.com>,
	Konrad Dybcio <konrad.dybcio@linaro.org>,
	linux-bluetooth@vger.kernel.org, linux-arm-msm@vger.kernel.org,
	netdev@vger.kernel.org, devicetree@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 1/4] dt-bindings: bluetooth: add new wcn3991 compatible to fix bd_addr
Date: Mon, 18 Mar 2024 15:45:45 +0100	[thread overview]
Message-ID: <ZfhTmQ6mOLR8eXA5@hovoldconsulting.com> (raw)
In-Reply-To: <CAA8EJpoxq6__DMcsuAEsnxBfPrrQBuu4ZgfULkok4KWSYVxuHQ@mail.gmail.com>

On Mon, Mar 18, 2024 at 04:17:24PM +0200, Dmitry Baryshkov wrote:
> On Mon, 18 Mar 2024 at 15:17, Johan Hovold <johan@kernel.org> wrote:
> > On Mon, Mar 18, 2024 at 03:00:40PM +0200, Dmitry Baryshkov wrote:
> > > On Mon, 18 Mar 2024 at 13:09, Johan Hovold <johan+linaro@kernel.org> wrote:
> > > > The only device out there that should be affected by this is the WCN3991
> > > > used in some Chromebooks. To maintain backwards compatibility, mark the
> > > > current compatible string as deprecated and add a new
> > > > 'qcom,wcn3991-bt-bdaddr-le' for firmware which conforms with the
> > > > binding.
> >
> > > This compatible doesn't describe new hardware kind. As such, I think,
> > > the better way would be to continue using qcom,wcn3991-bt compatible
> > > string + add some kind of qcom,bt-addr-le property.
> >
> > No, you can't handle backwards compatibility by *adding* a property.
> >
> > I wanted to avoid doing this, but if we have to support Google's broken
> > boot firmware for these devices, then this is how it needs to be done.
> 
> One hardware compat string per hardware type.

Again, no. Not when there is an incompatible change in the binding. Then
we add a new compatible string and deprecate the old binding.

Johan