netdev - Re: [PATCH v3 1/2] Bluetooth: Ignore HCI_ERROR_CANCELLED_BY

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Message-Id: <5F95A4B3-0002-414A-A397-520BF6089017@holtmann.org>
Date:   Tue, 16 Nov 2021 15:18:24 +0100
From:   Marcel Holtmann <marcel@...tmann.org>
To:     Archie Pusaka <apusaka@...gle.com>
Cc:     linux-bluetooth <linux-bluetooth@...r.kernel.org>,
        CrosBT Upstreaming <chromeos-bluetooth-upstreaming@...omium.org>,
        Archie Pusaka <apusaka@...omium.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Johan Hedberg <johan.hedberg@...il.com>,
        Luiz Augusto von Dentz <luiz.dentz@...il.com>,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH v3 1/2] Bluetooth: Ignore HCI_ERROR_CANCELLED_BY_HOST on
 adv set terminated event

Hi Archie,

> This event is received when the controller stops advertising,
> specifically for these three reasons:
> (a) Connection is successfully created (success).
> (b) Timeout is reached (error).
> (c) Number of advertising events is reached (error).
> (*) This event is NOT generated when the host stops the advertisement.
> Refer to the BT spec ver 5.3 vol 4 part E sec 7.7.65.18. Note that the
> section was revised from BT spec ver 5.0 vol 2 part E sec 7.7.65.18
> which was ambiguous about (*).
> 
> Some chips (e.g. RTL8822CE) send this event when the host stops the
> advertisement with status = HCI_ERROR_CANCELLED_BY_HOST (due to (*)
> above). This is treated as an error and the advertisement will be
> removed and userspace will be informed via MGMT event.
> 
> On suspend, we are supposed to temporarily disable advertisements,
> and continue advertising on resume. However, due to the behavior
> above, the advertisements are removed instead.
> 
> This patch returns early if HCI_ERROR_CANCELLED_BY_HOST is received.
> 
> Btmon snippet of the unexpected behavior:
> @ MGMT Command: Remove Advertising (0x003f) plen 1
>        Instance: 1
> < HCI Command: LE Set Extended Advertising Enable (0x08|0x0039) plen 6
>        Extended advertising: Disabled (0x00)
>        Number of sets: 1 (0x01)
>        Entry 0
>          Handle: 0x01
>          Duration: 0 ms (0x00)
>          Max ext adv events: 0
>> HCI Event: LE Meta Event (0x3e) plen 6
>      LE Advertising Set Terminated (0x12)
>        Status: Operation Cancelled by Host (0x44)
>        Handle: 1
>        Connection handle: 0
>        Number of completed extended advertising events: 5
>> HCI Event: Command Complete (0x0e) plen 4
>      LE Set Extended Advertising Enable (0x08|0x0039) ncmd 2
>        Status: Success (0x00)
> 
> Signed-off-by: Archie Pusaka <apusaka@...omium.org>
> 
> ---
> 
> (no changes since v2)
> 
> Changes in v2:
> * Split clearing HCI_LE_ADV into its own patch
> * Reword comments
> 
> include/net/bluetooth/hci.h |  1 +
> net/bluetooth/hci_event.c   | 12 ++++++++++++
> 2 files changed, 13 insertions(+)

patch has been applied to bluetooth-next tree.

Regards

Marcel