linux-kernel - Re: [PATCH v3 2/5] Bluetooth: add quirk for broken address properties

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Date: Tue, 19 Mar 2024 18:38:42 +0100
From: Johan Hovold <johan@...nel.org>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Cc: Doug Anderson <dianders@...omium.org>,
	Johan Hovold <johan+linaro@...nel.org>,
	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>,
	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
Subject: Re: [PATCH v3 2/5] Bluetooth: add quirk for broken address properties

On Tue, Mar 19, 2024 at 07:01:57PM +0200, Dmitry Baryshkov wrote:
> On Tue, 19 Mar 2024 at 18:26, Johan Hovold <johan@...nel.org> wrote:
> >
> > On Tue, Mar 19, 2024 at 09:10:23AM -0700, Doug Anderson wrote:
> > > On Tue, Mar 19, 2024 at 8:29 AM Johan Hovold <johan+linaro@...nel.org> wrote:
> >
> > > > +       /* When this quirk is set, the Bluetooth Device Address provided by
> > > > +        * the 'local-bd-address' fwnode property is incorrectly specified in
> > > > +        * big-endian order.
> > > > +        *
> > > > +        * This quirk can be set before hci_register_dev is called or
> > > > +        * during the hdev->setup vendor callback.
> > > > +        */
> > > > +       HCI_QUIRK_BDADDR_PROPERTY_BROKEN,
> > >
> > > Like with the binding, I feel like
> > > "HCI_QUIRK_BDADDR_PROPERTY_BACKWARDS" or
> > > "HCI_QUIRK_BDADDR_PROPERTY_SWAPPED" would be more documenting but I
> > > don't feel strongly.
> >
> > So, same reasoning here, this it not some quirk that people should go
> > around setting without first considering to fix their boot firmware.
> 
> The address can be considered broken in many different ways. The name
> should still be descriptive enough. If you want to specify that it is
> a broken behaviour, please consider something like BROKEN_BE.

I doubt that Qualcomm will be able come up with another way to break the
address property. They'd have to try real hard.

And this is an internal define which can be changed at any time. There's
also some worth in keeping it aligned with the DT property, which I'm
more open to renaming (e.g. if the DT maintainers thinks dropping the
vendor prefix makes sense).

The alternative I considered but rejected was something like
"local-bd-address-be" as that would be too neutral.

Perhaps "local-bd-address-reversed" would at least signal that something
is backwards, but I still fear that that may be too subtle.

Johan