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Date: Thu, 28 Dec 2023 13:10:51 +0100
From: Johan Hovold <johan@kernel.org>
To: Sven Peter <sven@svenpeter.dev>
Cc: Paul Menzel <pmenzel@molgen.mpg.de>, Felix Zhang <mrman@mrman314.tech>,
	linux-bluetooth@vger.kernel.org, stable@vger.kernel.org,
	Johan Hovold <johan+linaro@kernel.org>,
	Hector Martin <marcan@marcan.st>,
	Bagas Sanjaya <bagasdotme@gmail.com>,
	Alyssa Rosenzweig <alyssa@rosenzweig.io>,
	Marcel Holtmann <marcel@holtmann.org>,
	Johan Hedberg <johan.hedberg@gmail.com>,
	Luiz Augusto von Dentz <luiz.dentz@gmail.com>,
	Orlando Chamberlain <orlandoch.dev@gmail.com>, kekrby@gmail.com,
	admin@kodeit.net, Janne Grunau <j@jannau.net>,
	Aditya Garg <gargaditya08@live.com>, asahi@lists.linux.dev,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3] Bluetooth: Fix Bluetooth for BCM4377 on T2 Intel
 MacBooks
Message-ID: <ZY1ly_uB8huYl5jO@hovoldconsulting.com>
References: <AB87C916-9CF9-4B8C-AFF5-74CA4151C4FC@svenpeter.dev>
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In-Reply-To: <AB87C916-9CF9-4B8C-AFF5-74CA4151C4FC@svenpeter.dev>

On Thu, Dec 28, 2023 at 10:46:57AM +0100, Sven Peter wrote:

> > On Dec 27, 2023, at 11:30, Johan Hovold <johan@kernel.org> wrote:

> > The commit you tracked this down to restored the original semantics for
> > HCI_QUIRK_USE_BDADDR_PROPERTY, which means that it should only be set
> > for devices with an invalid address.
> > 
> > The Broadcom BCM4377 driver has so far been setting this flag
> > unconditionally which now potentially results in also valid addresses
> > being marked as invalid.
> > 
> > I've just sent a patch that makes sure to only mark invalid addresses as
> > invalid:
> > 
> > https://lore.kernel.org/lkml/20231227101003.10534-1-johan+linaro@kernel.org/
> > 
> > Note however that the flag still needs to be set in case your device
> > lacks storage for a unique device address so you cannot simply drop it
> > for some device classes as you do below (unless you are certain that
> > these devices will always have a valid address).

> We do know that though.
> 
> BCM4377 is present on Apple’s x86 Macs and always has internal storage
> for the address. If the board comes up without an address there’s nothing
> much we can do because the address isn’t provided by ACPI or anything
> else and setting the invalid address quirk for that situation seems appropriate.
> 
> BCM4378/4387 is present on Apple’s ARM Macs and never has internal storage.
> The address is always provided by our bootloader in the device tree.
> These should always unconditionally set HCI_QUIRK_USE_BDADDR_PROPERTY
> just like this patch does.

Ok, good, then this patch and the one I posted are mostly equivalent
assuming that the BCM4378/4387 return an invalid address during setup.

This patch may be preferred as it does not need to rely on such
assumptions, though.

Johan