linux-kernel - Re: [PATCH] Bluetooth: hci_sync: fix LE init stage 3 failure

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Message-ID: <CABBYNZJPG+-m5WwDLOBMpw-O+a-GY9RmNV6hiz7AQv_4=m66kQ@mail.gmail.com>
Date: Mon, 18 Nov 2024 10:28:35 -0500
From: Luiz Augusto von Dentz <luiz.dentz@...il.com>
To: André Groenewald <andre.groenewald@...eamunlimited.com>
Cc: marcel@...tmann.org, johan.hedberg@...il.com, 
	linux-bluetooth@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Bluetooth: hci_sync: fix LE init stage 3 failure

Hi André,

On Mon, Nov 18, 2024 at 10:19 AM André Groenewald
<andre.groenewald@...eamunlimited.com> wrote:
>
> A controller may indicate support for the extended advertising feature but
> doesn't support the HCI_LE_Read_Number_of_Supported_Advertising_Sets
> command, which will cause the initialization to fail.

It might be a good idea to mention the model and include the HCI trace
so it is easier for others to find out there is a fix for this
controller.

> Signed-off-by: André Groenewald <andre.groenewald@...eamunlimited.com>
> ---
>  net/bluetooth/hci_sync.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
>
> diff --git a/net/bluetooth/hci_sync.c b/net/bluetooth/hci_sync.c
> index c86f4e42e69c..c07be5813113 100644
> --- a/net/bluetooth/hci_sync.c
> +++ b/net/bluetooth/hci_sync.c
> @@ -4416,6 +4416,15 @@ static int hci_le_read_num_support_adv_sets_sync(struct hci_dev *hdev)
>         if (!ext_adv_capable(hdev))
>                 return 0;
>
> +       /* Checking for extended advertising capabilities is not enough; refine
> +        * by checking if the HCI_LE_Read_Number_of_Supported_Advertising_Sets
> +        * command is supported. Since this command is part of the LE init
> +        * stage 3, the initialization will fail whenever the command is not
> +        * supported for devices that indicate extended advertising features.
> +        */
> +       if (!(hdev->commands[36] & 0x80))
> +               return 0;

Is this enough though? How can we figure the number of sets supported?
Or we shall assume it is just 1? Otherwise it might be better to just
revert to using legacy advertising commands instead.

>         return __hci_cmd_sync_status(hdev,
>                                      HCI_OP_LE_READ_NUM_SUPPORTED_ADV_SETS,
>                                      0, NULL, HCI_CMD_TIMEOUT);
> --
> 2.34.1
>


-- 
Luiz Augusto von Dentz