linux-kernel - Re: [PATCH v3 3/5] Bluetooth: qca: fix device-address endianness

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Date: Tue, 19 Mar 2024 09:10:38 -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, stable@...r.kernel.org, 
	Nikita Travkin <nikita@...n.ru>
Subject: Re: [PATCH v3 3/5] Bluetooth: qca: fix device-address endianness

Hi,

On Tue, Mar 19, 2024 at 8:30 AM Johan Hovold <johan+linaro@...nel.org> wrote:
>
> The WCN6855 firmware on the Lenovo ThinkPad X13s expects the Bluetooth
> device address in big-endian order when setting it using the
> EDL_WRITE_BD_ADDR_OPCODE command.
>
> Presumably, this is the case for all non-ROME devices which all use the
> EDL_WRITE_BD_ADDR_OPCODE command for this (unlike the ROME devices which
> use a different command and expect the address in little-endian order).
>
> Reverse the little-endian address before setting it to make sure that
> the address can be configured using tools like btmgmt or using the
> 'local-bd-address' devicetree property.
>
> Note that this can potentially break systems with boot firmware which
> has started relying on the broken behaviour and is incorrectly passing
> the address via devicetree in big-endian order.
>
> Fixes: 5c0a1001c8be ("Bluetooth: hci_qca: Add helper to set device address")
> Cc: stable@...r.kernel.org      # 5.1
> Cc: Balakrishna Godavarthi <quic_bgodavar@...cinc.com>
> Cc: Matthias Kaehlcke <mka@...omium.org>
> Tested-by: Nikita Travkin <nikita@...n.ru> # sc7180
> Signed-off-by: Johan Hovold <johan+linaro@...nel.org>
> ---
>  drivers/bluetooth/btqca.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)

Personally, I'd prefer it if you didn't break bisectability with your
series. As it is, if someone applies just the first 3 patches they'll
end up with broken Bluetooth.

IMO the order should be:
1. Binding (currently patch #1)
2. Trogdor dt patch, which won't hurt on its own (currently patch #5)
3. Bluetooth subsystem patch handling the quirk (currently patch #2)
4. Qualcomm change to fix the endianness and handle the quirk squashed
into 1 patch (currently patch #3 + #4)

..and the patch that changes the Qualcomm driver should make it
obvious that it depends on the trogdor DT patch in the change
description.

With patches #3 and #4 combined, feel free to add my Reviewed-by tag
as both patches look fine to me.

-Doug