linux-kernel - Re: [PATCH] Bluetooth: qca: fix device-address endianness

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Message-ID: <ZcuQ2qRX0zsLSVRL@google.com>
Date: Tue, 13 Feb 2024 15:55:06 +0000
From: Matthias Kaehlcke <mka@...omium.org>
To: Johan Hovold <johan@...nel.org>
Cc: Luiz Augusto von Dentz <luiz.dentz@...il.com>,
	Marcel Holtmann <marcel@...tmann.org>,
	Johan Hedberg <johan.hedberg@...il.com>,
	Bjorn Andersson <quic_bjorande@...cinc.com>,
	Konrad Dybcio <konrad.dybcio@...aro.org>,
	linux-bluetooth@...r.kernel.org, linux-arm-msm@...r.kernel.org,
	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	Balakrishna Godavarthi <quic_bgodavar@...cinc.com>,
	Johan Hovold <johan+linaro@...nel.org>,
	Doug Anderson <dianders@...omium.org>,
	Stephen Boyd <swboyd@...omium.org>
Subject: Re: [PATCH] Bluetooth: qca: fix device-address endianness

On Tue, Feb 13, 2024 at 03:41:56PM +0100, Johan Hovold wrote:
> Hi Luiz,
> 
> On Wed, Dec 27, 2023 at 07:03:06PM +0100, Johan Hovold wrote:
> > The WCN6855 firmware on the Lenovo ThinkPad X13s expects the Bluetooth
> > device address in MSB 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 LSB 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 MSB 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>
> > Signed-off-by: Johan Hovold <johan+linaro@...nel.org>
> 
> Can we go ahead and merge this one to get this fixed in 6.8?
> 
> I've spoken to Bjorn Andersson at Qualcomm about this and he is in
> favour of doing so. The only people actually using the devicetree
> property should be the Chromium team and they control their own boot
> firmware and should be able to update it in lockstep (and Android uses
> some custom hacks to set the address that are not in mainline).

Unfortunately it's not as trivial as it sounds for Chrome OS. The boot
firmware is controlled by Chrome OS, however for any baseboard (e.g.
'trogdor') there is a larger number binary firmware packages, one
for every model derived from that baseboard. There can be dozens of
models. Chrome OS Firmware releases are qualified and rolled out per
model. FW qual may involve the ODM, usually there are multiple ODMs
per board. In an absolute emergency it would be possible to coordinate
a qual and synced rollout for all models, but it's definitely
non-trivial in terms of operations.