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

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Message-ID: <ZcuWQkmYK4Ax9kam@google.com>
Date: Tue, 13 Feb 2024 16:18:10 +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 05:03:15PM +0100, Johan Hovold wrote:
> On Tue, Feb 13, 2024 at 03:55:06PM +0000, Matthias Kaehlcke wrote:
> > On Tue, Feb 13, 2024 at 03:41:56PM +0100, Johan Hovold wrote:
> > > 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.
> 
> > > > 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.
> 
> Ok, fair enough.
> 
> Could you please provide a list of the compatible strings that you guys
> currently use and I can add new compatible strings for those, while
> keeping the current ones for backwards compatibility with older boot
> firmware?

'qcom,wcn3991-bt' should be the only impacted compatible string for
released devices.

Thanks for maintaining backwards compatibility, and sorry for the
inconvenience.