linux-kernel - Re: [PATCHv2] Bluetooth: quirk disabling LE Read Transmit Power

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Message-ID: <829A2DF8-818E-4AF1-84F9-49B5822F9146@live.com>
Date:   Sat, 6 Nov 2021 17:27:27 +0000
From:   Aditya Garg <gargaditya08@...e.com>
To:     Greg KH <gregkh@...uxfoundation.org>
CC:     Luiz Augusto von Dentz <luiz.dentz@...il.com>,
        Orlando Chamberlain <redecorating@...tonmail.com>,
        Daniel Winkler <danielwinkler@...gle.com>,
        Johan Hedberg <johan.hedberg@...el.com>,
        "linux-bluetooth@...r.kernel.org" <linux-bluetooth@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Marcel Holtmann <marcel@...tmann.org>,
        "regressions@...ts.linux.dev" <regressions@...ts.linux.dev>,
        Sonny Sasaka <sonnysasaka@...omium.org>
Subject: Re: [PATCHv2] Bluetooth: quirk disabling LE Read Transmit Power



> On 06-Nov-2021, at 5:19 PM, Greg KH <gregkh@...uxfoundation.org> wrote:
> 
> On Sat, Nov 06, 2021 at 09:41:28AM +0000, Aditya Garg wrote:
>> 
>> 
>>> On 06-Nov-2021, at 3:17 AM, Luiz Augusto von Dentz <luiz.dentz@...il.com> wrote:
>>> 
>>> Hi Orlando,
>>> 
>>> On Fri, Oct 1, 2021 at 1:56 AM Orlando Chamberlain
>>> <redecorating@...tonmail.com> wrote:
>>>> 
>>>> The LE Read Transmit Power command is Advertised on some Broadcom
>>>> controlers, but not supported. Using this command breaks Bluetooth
>>>> on the MacBookPro16,1 and iMac20,1. Added a quirk disabling LE Read
>>>> Transmit Power for these devices, based off their common chip id 150.
>>>> 
>>>> Link: https://lore.kernel.org/r/4970a940-211b-25d6-edab-21a815313954@protonmail.com
>>>> Signed-off-by: Orlando Chamberlain <redecorating@...tonmail.com>
>>>> ---
>>>> v1->v2: Clarified quirk description
>>>> 
>>>> drivers/bluetooth/btbcm.c   |  4 ++++
>>>> include/net/bluetooth/hci.h | 11 +++++++++++
>>>> net/bluetooth/hci_core.c    |  3 ++-
>>>> 3 files changed, 17 insertions(+), 1 deletion(-)
>>>> 
>>>> diff --git a/drivers/bluetooth/btbcm.c b/drivers/bluetooth/btbcm.c
>>>> index e4182acee488..4ecc50d93107 100644
>>>> --- a/drivers/bluetooth/btbcm.c
>>>> +++ b/drivers/bluetooth/btbcm.c
>>>> @@ -353,6 +353,10 @@ static int btbcm_read_info(struct hci_dev *hdev)
>>>>               return PTR_ERR(skb);
>>>> 
>>>>       bt_dev_info(hdev, "BCM: chip id %u", skb->data[1]);
>>>> +
>>>> +       if (skb->data[1] == 150)
>>>> +               set_bit(HCI_QUIRK_BROKEN_READ_TRANSMIT_POWER, &hdev->quirks);
>>>> +
>>>>       kfree_skb(skb);
>>>> 
>>>>       /* Read Controller Features */
>>>> diff --git a/include/net/bluetooth/hci.h b/include/net/bluetooth/hci.h
>>>> index b80415011dcd..6da9bd6b7259 100644
>>>> --- a/include/net/bluetooth/hci.h
>>>> +++ b/include/net/bluetooth/hci.h
>>>> @@ -246,6 +246,17 @@ enum {
>>>>        * HCI after resume.
>>>>        */
>>>>       HCI_QUIRK_NO_SUSPEND_NOTIFIER,
>>>> +
>>>> +       /* When this quirk is set, LE Read Transmit Power is disabled.
>>>> +        * This is mainly due to the fact that the HCI LE Read Transmit
>>>> +        * Power command is advertised, but not supported; these
>>>> +        * controllers often reply with unknown command and need a hard
>>>> +        * reset.
>>>> +        *
>>>> +        * This quirk can be set before hci_register_dev is called or
>>>> +        * during the hdev->setup vendor callback.
>>>> +        */
>>>> +       HCI_QUIRK_BROKEN_READ_TRANSMIT_POWER,
>>>> };
>>>> 
>>>> /* HCI device flags */
>>>> diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
>>>> index 8a47a3017d61..9a23fe7c8d67 100644
>>>> --- a/net/bluetooth/hci_core.c
>>>> +++ b/net/bluetooth/hci_core.c
>>>> @@ -742,7 +742,8 @@ static int hci_init3_req(struct hci_request *req, unsigned long opt)
>>>>                       hci_req_add(req, HCI_OP_LE_READ_ADV_TX_POWER, 0, NULL);
>>>>               }
>>>> 
>>>> -               if (hdev->commands[38] & 0x80) {
>>>> +               if (hdev->commands[38] & 0x80 &&
>>>> +                       !test_bit(HCI_QUIRK_BROKEN_READ_TRANSMIT_POWER, &hdev->quirks)) {
>>>>                       /* Read LE Min/Max Tx Power*/
>>>>                       hci_req_add(req, HCI_OP_LE_READ_TRANSMIT_POWER,
>>>>                                   0, NULL);
>>>> --
>>>> 2.33.0
>>> 
>>> Nowadays it is possible to treat errors such like this on a per
>>> command basis (assuming it is not essential for the init sequence):
>>> 
>>> diff --git a/include/net/bluetooth/hci.h b/include/net/bluetooth/hci.h
>>> index 979da5179ff4..f244f42cc609 100644
>>> --- a/include/net/bluetooth/hci.h
>>> +++ b/include/net/bluetooth/hci.h
>>> @@ -551,6 +551,7 @@ enum {
>>> #define HCI_LK_AUTH_COMBINATION_P256   0x08
>>> 
>>> /* ---- HCI Error Codes ---- */
>>> +#define HCI_ERROR_UNKNOWN_CMD          0x01
>>> #define HCI_ERROR_UNKNOWN_CONN_ID      0x02
>>> #define HCI_ERROR_AUTH_FAILURE         0x05
>>> #define HCI_ERROR_PIN_OR_KEY_MISSING   0x06
>>> diff --git a/net/bluetooth/hci_sync.c b/net/bluetooth/hci_sync.c
>> This diff cannot be applied to stable 5.15. Could you provide a patch capable of being applied to stable.
> 
> That is not needed until a patch is in Linus's tree.  Why do you need it
> earlier?
> 
Well not an emergency, but the issue of Bluetooth not working on some Apple Macs has been there for a long time. BTW, will this patch be there in Linus’s tree in the coming days?
> thanks,
> 
> greg k-h