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

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Date:   Sun, 7 Nov 2021 09:35:15 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Aditya Garg <gargaditya08@...e.com>
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 Sat, Nov 06, 2021 at 05:27:27PM +0000, Aditya Garg wrote:
> 
> 
> > 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?

That is up to the bluetooth maintainers, they have to accept it first.

thanks,

greg k-h