linux-kernel - Re: [PATCH v5 BlueZ 4/4] Bluetooth: Handle Slave Connection Interval Range AD

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Date:   Thu, 13 Apr 2017 21:40:05 +0300
From:   Luiz Augusto von Dentz <luiz.dentz@...il.com>
To:     Vinicius Costa Gomes <vinicius.gomes@...el.com>
Cc:     "Felipe F. Tonello" <eu@...ipetonello.com>,
        "linux-bluetooth@...r.kernel.org" <linux-bluetooth@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Marcel Holtmann <marcel@...tmann.org>,
        Johan Hedberg <johan.hedberg@...il.com>
Subject: Re: [PATCH v5 BlueZ 4/4] Bluetooth: Handle Slave Connection Interval
 Range AD

Hi,

On Thu, Apr 13, 2017 at 9:24 PM, Vinicius Costa Gomes
<vinicius.gomes@...el.com> wrote:
> Hi Felipe,
>
> "Felipe F. Tonello" <eu@...ipetonello.com> writes:
>
>> The Slave Connection Interval Range data type contains the Peripheral's
>> preferred connection interval range, for all logical connections.
>>
>> It is useful to parse it in the Kernel so there is no multiple calls to
>> MGMT interface to update the device connection parameters and subsequent
>> connection command call to this device will use proper connection
>> parameters. This saves context-switches and eliminates user-space to
>> update the connection parameters each time a device is found or
>> bluetoothd is restarted and so on. Also, there is no need for the
>> user-space to know care about it because if the slave device wishes to
>> persist with these parameters, it should use the L2CAP connection
>> parameters upade request upon a completed connection.
>
> nitpick: upade -> update
>
>>
>> Signed-off-by: Felipe F. Tonello <eu@...ipetonello.com>
>> ---
>>  net/bluetooth/mgmt.c | 53 ++++++++++++++++++++++++++++++++++++++++++++++++++++
>>  1 file changed, 53 insertions(+)
>>
>> diff --git a/net/bluetooth/mgmt.c b/net/bluetooth/mgmt.c
>> index 1fba2a03f8ae..ea5d6c85f173 100644
>> --- a/net/bluetooth/mgmt.c
>> +++ b/net/bluetooth/mgmt.c
>> @@ -7442,6 +7442,46 @@ static bool is_filter_match(struct hci_dev *hdev, s8 rssi, u8 *eir,
>>       return true;
>>  }
>>
>> +static bool has_eir_slave_conn_int(const u8 *eir_data, u8 eir_len,
>> +                                u16 *min_conn, u16 *max_conn)
>> +{
>> +     u16 len = 0;
>> +     const u8 EIR_SLAVE_CONN_INT = 0x12; /* Slave Connection Interval Range */
>> +
>> +     while (len < eir_len - 1) {
>> +             u8 field_len = eir_data[0];
>> +             const u8 *data;
>> +             u8 data_len;
>> +
>> +             /* Check for the end of EIR */
>> +             if (field_len == 0)
>> +                     break;
>> +
>> +             len += field_len + 1;
>> +
>> +             /* Do not continue EIR Data parsing if got
>> +              * incorrect length
>> +              */
>> +             if (len > eir_len)
>> +                     break;
>> +
>> +             data = &eir_data[2];
>> +             data_len = field_len - 1;
>> +
>> +             if (eir_data[1] == EIR_SLAVE_CONN_INT) {
>> +                     if (data_len < 4)
>> +                             break;
>> +                     *min_conn = le16_to_cpu(&data[0]);
>> +                     *max_conn = le16_to_cpu(&data[2]);
>> +                     return true;
>> +             }
>> +
>> +             eir_data += field_len + 1;
>> +     }
>> +
>> +     return false;
>> +}
>> +
>>  void mgmt_device_found(struct hci_dev *hdev, bdaddr_t *bdaddr, u8 link_type,
>>                      u8 addr_type, u8 *dev_class, s8 rssi, u32 flags,
>>                      u8 *eir, u16 eir_len, u8 *scan_rsp, u8 scan_rsp_len)
>> @@ -7449,6 +7489,7 @@ void mgmt_device_found(struct hci_dev *hdev, bdaddr_t *bdaddr, u8 link_type,
>>       char buf[512];
>>       struct mgmt_ev_device_found *ev = (void *)buf;
>>       size_t ev_size;
>> +     struct hci_conn *hcon;
>>
>>       /* Don't send events for a non-kernel initiated discovery. With
>>        * LE one exception is if we have pend_le_reports > 0 in which
>> @@ -7521,6 +7562,18 @@ void mgmt_device_found(struct hci_dev *hdev, bdaddr_t *bdaddr, u8 link_type,
>>       ev->eir_len = cpu_to_le16(eir_len + scan_rsp_len);
>>       ev_size = sizeof(*ev) + eir_len + scan_rsp_len;
>>
>> +     /* Search for Slave Connection Interval AD */
>> +     hcon = hci_conn_hash_lookup_le(hdev, bdaddr, addr_type);
>> +     if (hcon) {
>> +             u16 min_conn_int, max_conn_int;
>> +
>> +             if (has_eir_slave_conn_int(ev->eir, ev->eir_len,
>> +                                        &min_conn_int, &max_conn_int)) {
>> +                     hcon->le_conn_min_interval = min_conn_int;
>> +                     hcon->le_conn_max_interval = max_conn_int;
>> +             }
>> +     }
>> +
>
> It's been some time that I looked at this code, so I could be missing
> something, but I got the feeling that this part would make more sense if
> it was at process_adv_report(), there's even the check for a pending
> connection, so no need to redo that here.

Actually I would use the AD only in case the device is marked for
auto-connect or there is a connection pending, so the parameters are
only used for the connection alone and are not persisted.

> Apart from this, the series looks good.
>
>
>>       mgmt_event(MGMT_EV_DEVICE_FOUND, hdev, ev, ev_size, NULL);
>>  }
>>
>> --
>> 2.12.2
>>
>> --
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>
> Cheers,
> --
> Vinicius



-- 
Luiz Augusto von Dentz