linux-kernel - Re: [PATCH v6 2/2] btbcm: disable read tx power for affected Macs with the T2 Security chip

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Date:   Tue, 30 Nov 2021 10:28:19 +0000
From:   Orlando Chamberlain <redecorating@...tonmail.com>
To:     Aditya Garg <gargaditya08@...e.com>
Cc:     Marcel Holtmann <marcel@...tmann.org>,
        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 v6 2/2] btbcm: disable read tx power for affected Macs with the T2 Security chip

On Tue, 30 Nov 2021 01:00:43 +1100
"Aditya Garg" <gargaditya08@...e.com> wrote:
> From: Aditya Garg <gargaditya08@...e.com>
> 
> 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>
> Reported-by: Orlando Chamberlain <redecorating@...tonmail.com>
> Link:
> https://lore.kernel.org/r/4970a940-211b-25d6-edab-21a815313954@protonmail.com
> Fixes: 7c395ea521e6 ("Bluetooth: Query LE tx power on startup")
> ---

It's hard to tell what the differences between versions of this patch
are. This spot here after the "---" is often used for a change log
(e.g. "v5->v6: Made change X and change Y"), so it would be useful to
have that if you can add one in future patches. I think someone may have
mentioned this earlier.

>  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;

This line seems to produce a compiler warning:

drivers/bluetooth/btbcm.c: In function ‘btbcm_read_info’:
drivers/bluetooth/btbcm.c:384:22: warning: empty declaration with type
qualifier does not redeclare  tag
  384 |         const struct dmi_system_id;
      |                      ^~~~~~~~~~~~~

I think Marcel mentioned this line could be removed.

The two patches make Bluetooth work on my MacBookPro16,1, with and without
that line.

Tested-by: Orlando Chamberlain <redecorating@...tonmail.com>

> 
>  	/* 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;
>  }
> 
> 

-- 

Thanks,

Orlando