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

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Message-ID: <YYZr14zwHnd52rQ7@kroah.com>
Date:   Sat, 6 Nov 2021 12:49:43 +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 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?

thanks,

greg k-h