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    SubjectRe: [PATCHv2] Bluetooth: quirk disabling LE Read Transmit Power
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    Hi, this is your Linux kernel regression tracker speaking again.

    On 19.11.21 17:59, Aditya Garg wrote:
    >> On 18-Nov-2021, at 12:31 AM, Marcel Holtmann <marcel@holtmann.org> wrote:
    >>>> 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?
    >>>
    >>> I think we should be able to quirk based off the acpi _CID "apple-uart-blth"
    >>> or _HID "BCM2E7C". Marcel suggested quirking based of the acpi table here
    >>> https://lore.kernel.org/linux-bluetooth/1D2217A9-EA73-4D93-8D0B-5BC2718D4788@holtmann.org/
    >>>
    >>> This would catch some unaffected Macs, but they don't support the LE Read
    >>> 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).
    >>>
    >>> 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.
    >>>
    >>> It might be simpler to make it ignore the Unknown Command error, like
    >>> in this patch https://lore.kernel.org/linux-bluetooth/CABBYNZLjSfcG_KqTEbL6NOSvHhA5-b1t_S=3FQP4=GwW21kuzg@mail.gmail.com/
    >>> however that only applies on bluetooth-next and needed the status it
    >>> checks for to be -56, not 0x01.
    >>
    >> 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 as
    >> such.
    > Well all I can do is provide you any logs or information I can. But we do really wish to get this regression fixed soon.
    >>
    >> The question is just how we quirk it.

    This thread once again looks stalled and smells a lot like "everyone
    agrees that his should be fixed, but afaics nobody submitted a fix or
    committed to work on one". Please speak up if my impression is wrong, as
    this is a regression and thus needs to be fixed, ideally quickly. Part
    of my job is to make that happen and thus remind developers and
    maintainers about this until we have a fix.

    Ciao, Thorsten

    #regzbot title bluetooth: "Query LE tx power on startup" broke Bluetooth
    on MacBookPro16,1
    #regzbot poke

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