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SubjectRe: [PATCHv2] Bluetooth: quirk disabling LE Read Transmit Power
Hi Orlando,

On Fri, Oct 1, 2021 at 1:56 AM Orlando Chamberlain
<redecorating@protonmail.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@protonmail.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
index bb88d31d2212..9c697e058974 100644
--- a/net/bluetooth/hci_sync.c
+++ b/net/bluetooth/hci_sync.c
@@ -3325,11 +3325,18 @@ static int
hci_le_read_adv_tx_power_sync(struct hci_dev *hdev)
/* Read LE Min/Max Tx Power*/
static int hci_le_read_tx_power_sync(struct hci_dev *hdev)
{
+ int status;
+
if (!(hdev->commands[38] & 0x80))
return 0;

- return __hci_cmd_sync_status(hdev, HCI_OP_LE_READ_TRANSMIT_POWER,
- 0, NULL, HCI_CMD_TIMEOUT);
+ status = __hci_cmd_sync_status(hdev, HCI_OP_LE_READ_TRANSMIT_POWER,
+ 0, NULL, HCI_CMD_TIMEOUT);
+ /* Ignore if command is not really supported */
+ if (status == HCI_ERROR_UNKNOWN_CMD)
+ return 0;
+
+ return status;
}

/* Read LE Accept List Size */
Anyway, it would probably be worth pointing out to the vendor they
have a broken firmware if they do mark the command as supported but
return such error.

--
Luiz Augusto von Dentz

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