netdev - Re: [PATCH v1 1/5] Bluetooth: advmon offload MSFT add rssi support

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Message-Id: <14E449EF-6E91-43BF-9477-61B29B20783A@holtmann.org>
Date:   Mon, 7 Dec 2020 10:56:50 +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>,
        Miao-chen Chou <mcchou@...omium.org>,
        Yun-Hao Chung <howardchung@...gle.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Johan Hedberg <johan.hedberg@...il.com>,
        LKML <linux-kernel@...r.kernel.org>,
        "open list:NETWORKING [GENERAL]" <netdev@...r.kernel.org>
Subject: Re: [PATCH v1 1/5] Bluetooth: advmon offload MSFT add rssi support

Hi Archie,

>>>>> MSFT needs rssi parameter for monitoring advertisement packet,
>>>>> therefore we should supply them from mgmt.
>>>>> 
>>>>> Signed-off-by: Archie Pusaka <apusaka@...omium.org>
>>>>> Reviewed-by: Miao-chen Chou <mcchou@...omium.org>
>>>>> Reviewed-by: Yun-Hao Chung <howardchung@...gle.com>
>>>> 
>>>> I don’t need any Reviewed-by if they are not catching an obvious user API breakage.
>>>> 
>>>>> ---
>>>>> 
>>>>> include/net/bluetooth/hci_core.h | 9 +++++++++
>>>>> include/net/bluetooth/mgmt.h     | 9 +++++++++
>>>>> net/bluetooth/mgmt.c             | 8 ++++++++
>>>>> 3 files changed, 26 insertions(+)
>>>>> 
>>>>> diff --git a/include/net/bluetooth/hci_core.h b/include/net/bluetooth/hci_core.h
>>>>> index 9873e1c8cd16..42d446417817 100644
>>>>> --- a/include/net/bluetooth/hci_core.h
>>>>> +++ b/include/net/bluetooth/hci_core.h
>>>>> @@ -246,8 +246,17 @@ struct adv_pattern {
>>>>>     __u8 value[HCI_MAX_AD_LENGTH];
>>>>> };
>>>>> 
>>>>> +struct adv_rssi_thresholds {
>>>>> +     __s8 low_threshold;
>>>>> +     __s8 high_threshold;
>>>>> +     __u16 low_threshold_timeout;
>>>>> +     __u16 high_threshold_timeout;
>>>>> +     __u8 sampling_period;
>>>>> +};
>>>>> +
>>>>> struct adv_monitor {
>>>>>     struct list_head patterns;
>>>>> +     struct adv_rssi_thresholds rssi;
>>>>>     bool            active;
>>>>>     __u16           handle;
>>>>> };
>>>>> diff --git a/include/net/bluetooth/mgmt.h b/include/net/bluetooth/mgmt.h
>>>>> index d8367850e8cd..dc534837be0e 100644
>>>>> --- a/include/net/bluetooth/mgmt.h
>>>>> +++ b/include/net/bluetooth/mgmt.h
>>>>> @@ -763,9 +763,18 @@ struct mgmt_adv_pattern {
>>>>>     __u8 value[31];
>>>>> } __packed;
>>>>> 
>>>>> +struct mgmt_adv_rssi_thresholds {
>>>>> +     __s8 high_threshold;
>>>>> +     __le16 high_threshold_timeout;
>>>>> +     __s8 low_threshold;
>>>>> +     __le16 low_threshold_timeout;
>>>>> +     __u8 sampling_period;
>>>>> +} __packed;
>>>>> +
>>>>> #define MGMT_OP_ADD_ADV_PATTERNS_MONITOR      0x0052
>>>>> struct mgmt_cp_add_adv_patterns_monitor {
>>>>>     __u8 pattern_count;
>>>>> +     struct mgmt_adv_rssi_thresholds rssi;
>>>>>     struct mgmt_adv_pattern patterns[];
>>>>> } __packed;
>>>> 
>>>> This is something we can not do. It breaks an userspace facing API. Is the mgmt opcode 0x0052 in an already released kernel?
>>> 
>>> Yes, the opcode does exist in an already released kernel.
>>> 
>>> The DBus method which accesses this API is put behind the experimental
>>> flag, therefore we expect they are flexible enough to support changes.
>>> Previously, we already had a discussion in an email thread with the
>>> title "Offload RSSI tracking to controller", and the outcome supports
>>> this change.
>>> 
>>> Here is an excerpt of the discussion.
>> 
>> it doesn’t matter. This is fixed API now and so we can not just change it. The argument above is void. What matters if it is in already released kernel.
> 
> If that is the case, do you have a suggestion to allow RSSI to be
> considered when monitoring advertisement? Would a new MGMT opcode with
> these parameters suffice?

its the only way.

Regards

Marcel