linux-kernel - Re: [PATCH v3 1/5] dt-bindings: bluetooth: add 'qcom,local-bd-address-broken'

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

Hi,

On Tue, Mar 19, 2024 at 8:29 AM Johan Hovold <johan+linaro@...nel.org> 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@...nel.org>
> ---
>  .../devicetree/bindings/net/bluetooth/qualcomm-bluetooth.yaml  | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/net/bluetooth/qualcomm-bluetooth.yaml b/Documentation/devicetree/bindings/net/bluetooth/qualcomm-bluetooth.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 order

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@...omium.org>