From:   Aditya Garg <gargaditya08@live.com>
To:     Marcel Holtmann <marcel@holtmann.org>
CC:     Orlando Chamberlain <redecorating@protonmail.com>,
        Thorsten Leemhuis <regressions@leemhuis.info>,
        Daniel Winkler <danielwinkler@google.com>,
        Greg KH <gregkh@linuxfoundation.org>,
        Johan Hedberg <johan.hedberg@intel.com>,
        "linux-bluetooth@vger.kernel.org" <linux-bluetooth@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Luiz Augusto von Dentz <luiz.dentz@gmail.com>,
        "regressions@lists.linux.dev" <regressions@lists.linux.dev>,
        "sonnysasaka@chromium.org" <sonnysasaka@chromium.org>
Subject: Re: [PATCHv2] Bluetooth: quirk disabling LE Read Transmit Power
Thread-Topic: [PATCHv2] Bluetooth: quirk disabling LE Read Transmit Power
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Date:   Fri, 19 Nov 2021 16:59:32 +0000
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> On 18-Nov-2021, at 12:31 AM, Marcel Holtmann <marcel@holtmann.org> wrote:
>=20
> Hi Orlando,
>=20
>>> So if this just affects two macs, why can't the fix be realized as a
>>> quirk that is only enabled on those two systems? Or are they impossible
>>> to detect clearly via DMI data or something like that?
>>=20
>> I think we should be able to quirk based off the acpi _CID "apple-uart-b=
lth"
>> or _HID "BCM2E7C". Marcel suggested quirking based of the acpi table her=
e
>> https://lore.kernel.org/linux-bluetooth/1D2217A9-EA73-4D93-8D0B-5BC2718D=
4788@holtmann.org/
>>=20
>> This would catch some unaffected Macs, but they don't support the LE Rea=
d
>> Transmit Power command anyway (the affected macs were released after it
>> was added to the Bluetooth spec, while the unaffected Macs were released
>> before it was added to the spec, and thus don't support it).
>>=20
>> I'm not sure how to go about applying a quirk based off this, there are
>> quirks in drivers/bluetooth/hci_bcm.c (no_early_set_baudrate and
>> drive_rts_on_open), but they don't seem to be based off acpi ids.
>>=20
>> It might be simpler to make it ignore the Unknown Command error, like
>> in this patch https://lore.kernel.org/linux-bluetooth/CABBYNZLjSfcG_KqTE=
bL6NOSvHhA5-b1t_S=3D3FQP4=3DGwW21kuzg@mail.gmail.com/
>> however that only applies on bluetooth-next and needed the status it
>> checks for to be -56, not 0x01.
>=20
> so we abstain from try-and-error sending of commands. The Bluetooth spec
> has a list of supported commands that a host can query for a reason. This
> is really broken behavior of the controller and needs to be pointed out a=
s
> such.
Well all I can do is provide you any logs or information I can. But we do r=
eally wish to get this regression fixed soon.
>=20
> The question is just how we quirk it.
>=20
> Regards
>=20
> Marcel
>=20