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

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Date:   Sat, 5 Dec 2020 00:34:59 +0800
From:   Archie Pusaka <apusaka@...gle.com>
To:     Marcel Holtmann <marcel@...tmann.org>
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 Marcel,

On Fri, 4 Dec 2020 at 17:51, Marcel Holtmann <marcel@...tmann.org> wrote:
>
> 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?
#define MGMT_OP_ADD_ADV_PATTERNS_MONITOR_RSSI 0x005?
struct mgmt_cp_add_adv_patterns_monitor {
    __u8 pattern_count;
    struct mgmt_adv_rssi_thresholds rssi;
    struct mgmt_adv_pattern patterns[];
} __packed;

Thanks,
Archie