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References: <20240319152926.1288-1-johan+linaro@kernel.org> <20240319152926.1288-2-johan+linaro@kernel.org>
In-Reply-To: <20240319152926.1288-2-johan+linaro@kernel.org>
From: Doug Anderson <dianders@chromium.org>
Date: Tue, 19 Mar 2024 09:10:08 -0700
Message-ID: <CAD=FV=XJ+yAvDn5NyfCSJdg+DujPrWO+DZu=BmcqbJS-ugEGMg@mail.gmail.com>
Subject: Re: [PATCH v3 1/5] dt-bindings: bluetooth: add 'qcom,local-bd-address-broken'
To: Johan Hovold <johan+linaro@kernel.org>
Cc: Marcel Holtmann <marcel@holtmann.org>, Luiz Augusto von Dentz <luiz.dentz@gmail.com>, 
	Bjorn Andersson <andersson@kernel.org>, Rob Herring <robh+dt@kernel.org>, 
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>, Conor Dooley <conor+dt@kernel.org>, 
	cros-qcom-dts-watchers@chromium.org, Konrad Dybcio <konrad.dybcio@linaro.org>, 
	Johan Hedberg <johan.hedberg@gmail.com>, 
	Balakrishna Godavarthi <quic_bgodavar@quicinc.com>, Matthias Kaehlcke <mka@chromium.org>, 
	Rocky Liao <quic_rjliao@quicinc.com>, Dmitry Baryshkov <dmitry.baryshkov@linaro.org>, 
	linux-bluetooth@vger.kernel.org, netdev@vger.kernel.org, 
	devicetree@vger.kernel.org, linux-arm-msm@vger.kernel.org, 
	linux-kernel@vger.kernel.org
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Hi,

On Tue, Mar 19, 2024 at 8:29=E2=80=AFAM Johan Hovold <johan+linaro@kernel.o=
rg> wrote:
>
> Several Qualcomm Bluetooth controllers lack persistent storage for the
> device address and instead one can be provided by the boot firmware
> using the 'local-bd-address' devicetree property.
>
> The Bluetooth bindings clearly states that the address should be
> specified in little-endian order, but due to a long-standing bug in the
> Qualcomm driver which reversed the address some boot firmware has been
> providing the address in big-endian order instead.
>
> The only device out there that should be affected by this is the WCN3991
> used in some Chromebooks.
>
> Add a 'qcom,local-bd-address-broken' property which can be set on these
> platforms to indicate that the boot firmware is using the wrong byte
> order.
>
> Note that ChromeOS always updates the kernel and devicetree in lockstep
> so that there is no need to handle backwards compatibility with older
> devicetrees.
>
> Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
> ---
>  .../devicetree/bindings/net/bluetooth/qualcomm-bluetooth.yaml  | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/net/bluetooth/qualcomm-blu=
etooth.yaml b/Documentation/devicetree/bindings/net/bluetooth/qualcomm-blue=
tooth.yaml
> index eba2f3026ab0..e099ef83e7b1 100644
> --- a/Documentation/devicetree/bindings/net/bluetooth/qualcomm-bluetooth.=
yaml
> +++ b/Documentation/devicetree/bindings/net/bluetooth/qualcomm-bluetooth.=
yaml
> @@ -94,6 +94,9 @@ properties:
>
>    local-bd-address: true
>
> +  qcom,local-bd-address-broken: true
> +    description: >
> +      boot firmware is incorrectly passing the address in big-endian ord=
er

Personally, I feel like "qcom,local-bd-address-backwards" or
"qcom,local-bd-address-swapped" would be more documenting but I don't
feel super strongly about it. I guess "broken" makes it more obvious
that this is not just a normal variant that someone should use. If DT
binding folks are happy, I'm happy enough with this solution.

Reviewed-by: Douglas Anderson <dianders@chromium.org>