linux-kernel - Re: [PATCH v3 resend 2/2] btbcm: disable read tx power for affected Macs with the T2 Security chip

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Message-Id: <BEB98DAF-0AEE-4758-A6AC-33F23D11D91A@holtmann.org>
Date:   Mon, 29 Nov 2021 12:03:27 +0100
From:   Marcel Holtmann <marcel@...tmann.org>
To:     Aditya Garg <gargaditya08@...e.com>
Cc:     Greg KH <gregkh@...uxfoundation.org>,
        Thorsten Leemhuis <regressions@...mhuis.info>,
        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@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Luiz Augusto von Dentz <luiz.dentz@...il.com>,
        "regressions@...ts.linux.dev" <regressions@...ts.linux.dev>,
        "sonnysasaka@...omium.org" <sonnysasaka@...omium.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: Re: [PATCH v3 resend 2/2] btbcm: disable read tx power for affected
 Macs with the T2 Security chip

Hi Aditya,

> Some Macs with the T2 security chip had Bluetooth not working.
> To fix it we add DMI based quirks to disable querying of LE Tx power.
> 
> Signed-off-by: Aditya Garg <gargaditya08@...e.com>
> ---
> drivers/bluetooth/btbcm.c | 40 +++++++++++++++++++++++++++++++++++++++
> 1 file changed, 40 insertions(+)
> 
> diff --git a/drivers/bluetooth/btbcm.c b/drivers/bluetooth/btbcm.c
> index e4182acee488c5..40f7c9c5cf0a5a 100644
> --- a/drivers/bluetooth/btbcm.c
> +++ b/drivers/bluetooth/btbcm.c
> @@ -8,6 +8,7 @@
> 
> #include <linux/module.h>
> #include <linux/firmware.h>
> +#include <linux/dmi.h>
> #include <asm/unaligned.h>
> 
> #include <net/bluetooth/bluetooth.h>
> @@ -343,9 +344,44 @@ static struct sk_buff *btbcm_read_usb_product(struct hci_dev *hdev)
> 	return skb;
> }
> 
> +static const struct dmi_system_id disable_broken_read_transmit_power[] = {
> +	{
> +		 .matches = {
> +			DMI_MATCH(DMI_BOARD_VENDOR, "Apple Inc."),
> +			DMI_MATCH(DMI_PRODUCT_NAME, "MacBookPro16,1"),
> +		},
> +	},
> +	{
> +		 .matches = {
> +			DMI_MATCH(DMI_BOARD_VENDOR, "Apple Inc."),
> +			DMI_MATCH(DMI_PRODUCT_NAME, "MacBookPro16,2"),
> +		},
> +	},
> +	{
> +		 .matches = {
> +			DMI_MATCH(DMI_BOARD_VENDOR, "Apple Inc."),
> +			DMI_MATCH(DMI_PRODUCT_NAME, "MacBookPro16,4"),
> +		},
> +	},
> +	{
> +		 .matches = {
> +			DMI_MATCH(DMI_BOARD_VENDOR, "Apple Inc."),
> +			DMI_MATCH(DMI_PRODUCT_NAME, "iMac20,1"),
> +		},
> +	},
> +	{
> +		 .matches = {
> +			DMI_MATCH(DMI_BOARD_VENDOR, "Apple Inc."),
> +			DMI_MATCH(DMI_PRODUCT_NAME, "iMac20,2"),
> +		},
> +	},
> +	{ }
> +};
> +
> static int btbcm_read_info(struct hci_dev *hdev)
> {
> 	struct sk_buff *skb;
> +	const struct dmi_system_id *dmi_id;

this variable is not needed.

> 
> 	/* Read Verbose Config Version Info */
> 	skb = btbcm_read_verbose_config(hdev);
> @@ -363,6 +399,10 @@ static int btbcm_read_info(struct hci_dev *hdev)
> 	bt_dev_info(hdev, "BCM: features 0x%2.2x", skb->data[1]);
> 	kfree_skb(skb);
> 
> +	/* Read DMI and disable broken Read LE Min/Max Tx Power */
> +	if (dmi_first_match(disable_broken_read_transmit_power))
> +		set_bit(HCI_QUIRK_BROKEN_READ_TRANSMIT_POWER, &hdev->quirks);
> +
> 	return 0;
> }

Regards

Marcel