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Subject: Re: [PATCH 2/6] btbcm: disable read tx power for MacBook Pro 16,1 (16
 inch, 2019)
From:   Marcel Holtmann <marcel@holtmann.org>
In-Reply-To: <5B9FF471-42DD-44DA-A9CE-0A83BA7A4212@live.com>
Date:   Mon, 29 Nov 2021 09:08:16 +0100
Cc:     Thorsten Leemhuis <regressions@leemhuis.info>,
        Orlando Chamberlain <redecorating@protonmail.com>,
        Daniel Winkler <danielwinkler@google.com>,
        Greg KH <gregkh@linuxfoundation.org>,
        Johan Hedberg <johan.hedberg@intel.com>,
        "linux-bluetooth@vger.kernel.org" <linux-bluetooth@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Luiz Augusto von Dentz <luiz.dentz@gmail.com>,
        "regressions@lists.linux.dev" <regressions@lists.linux.dev>,
        "sonnysasaka@chromium.org" <sonnysasaka@chromium.org>,
        "stable@vger.kernel.org" <stable@vger.kernel.org>
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 <20211116090128.17546-1-redecorating@protonmail.com>
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To:     Aditya Garg <gargaditya08@live.com>
Precedence: bulk

Hi Aditya,

> Bluetooth on Apple MacBook Pro 16,1 is unable to start due to LE Min/Max Tx Power being queried on startup. Add a DMI based quirk so that it is disabled.

list all the MacBooks that you found problematic right now. We add the
initial as a large batch instead of all individual.

> 
> Signed-off-by: Aditya Garg <gargaditya08@live.com>
> Tested-by: Aditya Garg <gargaditya08@live.com>
> ---
> drivers/bluetooth/btbcm.c | 20 ++++++++++++++++++++
> 1 file changed, 20 insertions(+)
> 
> diff --git a/drivers/bluetooth/btbcm.c b/drivers/bluetooth/btbcm.c
> index e4182acee488c5..c1b0ca63880a68 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 +344,23 @@ 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[] = {
> +	{
> +		/* Match for Apple MacBook Pro 16,1 which needs
> +		 * Read LE Min/Max Tx Power to be disabled.
> +		 */

Actually leave the comment out. You are not adding any value that isn’t
already in the variable name or the DMI. It is just repeating the obvious.

> +		 .matches = {
> +			DMI_MATCH(DMI_BOARD_VENDOR, "Apple Inc."),
> +			DMI_MATCH(DMI_PRODUCT_NAME, "MacBookPro16,1"),
> +		},
> +	},
> +	{ }
> +};
> +
> static int btbcm_read_info(struct hci_dev *hdev)
> {
> 	struct sk_buff *skb;
> +	const struct dmi_system_id *dmi_id;
> 
> 	/* Read Verbose Config Version Info */
> 	skb = btbcm_read_verbose_config(hdev);
> @@ -362,6 +377,11 @@ 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 */
> +	dmi_id = dmi_first_match(disable_broken_read_transmit_power);
> +	if (dmi_id)
> +		set_bit(HCI_QUIRK_BROKEN_READ_TRANSMIT_POWER, &hdev->quirks);

	if (dmi_first_match(..))
		set_bit(.., &hdev->quirks);

There is really no need to have a variable for this.

Regards

Marcel