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From: Luiz Augusto von Dentz <luiz.dentz@gmail.com>
Date: Mon, 19 Feb 2018 12:31:52 +0200
Message-ID: <CABBYNZ+MMgCo2m-3bgdq6Ww3vb5w3pCKgubrvjryu4b1SPwJEA@mail.gmail.com>
Subject: Re: [PATCH 2/4 v4] doc/mgmt-api: Add support for Set Phy
 Configuration command
To: Jaganath K <jaganath.k.os@gmail.com>
Cc: =?UTF-8?Q?=C5=81ukasz_Rymanowski?= <lukasz.rymanowski@codecoup.pl>,
        "open list:BLUETOOTH DRIVERS" <linux-bluetooth@vger.kernel.org>,
        Jaganath Kanakkassery <jaganathx.kanakkassery@intel.com>
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Sender: linux-bluetooth-owner@vger.kernel.org
List-ID: <linux-bluetooth.vger.kernel.org>

Hi Jaganath,

On Mon, Feb 19, 2018 at 12:09 PM, Jaganath K <jaganath.k.os@gmail.com> wrot=
e:
> Hi Lukasz,
>
> On Mon, Feb 19, 2018 at 3:28 PM, =C5=81ukasz Rymanowski
> <lukasz.rymanowski@codecoup.pl> wrote:
>> Hi Jaganath,
>>
>> On 19 February 2018 at 10:25, Jaganath K <jaganath.k.os@gmail.com> wrote=
:
>>> Hi Luiz,
>>>
>>>
>>> On Mon, Feb 19, 2018 at 2:17 PM, Luiz Augusto von Dentz
>>> <luiz.dentz@gmail.com> wrote:
>>>> Hi Jaganath,
>>>>
>>>> On Fri, Feb 16, 2018 at 5:40 AM, Jaganath K <jaganath.k.os@gmail.com> =
wrote:
>>>>> Hi Marcel,
>>>>>
>>>>>
>>>>> On Wed, Nov 29, 2017 at 12:22 PM, Jaganath Kanakkassery
>>>>> <jaganath.k.os@gmail.com> wrote:
>>>>>> This also adds PHY Configuration Changed Event.
>>>>>> ---
>>>>>>  doc/mgmt-api.txt | 52 +++++++++++++++++++++++++++++++++++++++++++++=
+++++++
>>>>>>  1 file changed, 52 insertions(+)
>>>>>>
>>>>>> diff --git a/doc/mgmt-api.txt b/doc/mgmt-api.txt
>>>>>> index c07c48c..628ff18 100644
>>>>>> --- a/doc/mgmt-api.txt
>>>>>> +++ b/doc/mgmt-api.txt
>>>>>> @@ -2940,9 +2940,46 @@ Get PHY Configuration Command
>>>>>>         LE 1M TX and LE 1M RX would be supported by default.
>>>>>>
>>>>>>         This command is only available for LE capable controllers.
>>>>>> +        It will return Not Supported otherwise.
>>>>>> +
>>>>>> +        Possible errors:        Not Supported
>>>>>> +                               Invalid Index
>>>>>> +
>>>>>> +Set PHY Configuration Command
>>>>>> +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D
>>>>>> +
>>>>>> +       Command Code:           0x0044
>>>>>> +       Controller Index:       <controller id>
>>>>>> +       Command Parameters:     Default_phys (2 Octet)
>>>>>> +       Return Parameters:
>>>>>> +
>>>>>> +       This command is used to set the default phy to the controlle=
r.
>>>>>> +
>>>>>> +       This will be stored and used for all the subsequent scanning
>>>>>> +       and connection initiation.
>>>>>> +
>>>>>> +       The list of supported PHYs can be retrieved via the
>>>>>> +       Get PHY Configuration command. Selecting unsupported PHYs wi=
ll
>>>>>> +       result in an Invalid Parameters error.
>>>>>> +
>>>>>> +       This can be called at any point to change the preferred PHYs=
.
>>>>>> +
>>>>>> +       Default_phy is a bitmask with the following bits.
>>>>>> +               0       LE 1M TX
>>>>>> +               1       LE 1M RX
>>>>>> +               2       LE 2M TX
>>>>>> +               3       LE 2M RX
>>>>>> +               4       LE CODED TX
>>>>>> +               5       LE CODED RX
>>>>>> +
>>>>>> +       This command generates a Command Complete event on success
>>>>>> +       or a Command Status event on failure.
>>>>>> +
>>>>>> +       This command is only available for LE capable controllers.
>>>>>>         It will return Not Supported otherwise.
>>>>>>
>>>>>>         Possible errors:        Not Supported
>>>>>> +                               Invalid Parameters
>>>>>>                                 Invalid Index
>>>>>>
>>>>>
>>>>> I think there is a limitation with current API proposal, user cannot =
do extended
>>>>> scanning in only 1M (to scan secondary channel in 1M) since with 1M w=
e will
>>>>> switch to legacy scanning.
>>>>
>>>> Why do we have to switch to legacy scanning for 1M? It seems it would
>>>> be possible to use extended scanning whenever it is supported
>>>> regardless of the PHY, or perhaps the spec imposes limitations to
>>>> certain PHYs? Coded perhaps?
>>>>
>>>
>>> The idea is to enable application to use legacy scanning even if
>>> controller supports
>>> extended. (ie if application dont want extended features to be used)
>>> and unlike advertising
>>> legacy scanning can not be emulated using extended scanning.
>>
>> Bluetooth controller which is doing extended scanning will report legacy
>> advertisings as well. It will just use Extended Advertising Report
>> Event for this purpose and Linux Kernel should handle it.
>>
>
> Yes, but the idea here is more on perspective of power savings
> where in application dont want to scan on secondary channels itself and
> API should support it.

I would agree if this affects passive scanning, but in that case we
can probably program the scan type when adding a device or only really
scan on primary channel since the purpose is to connect it doesn't
really matter what is on the secondary channels, for active scanning I
don't think we would be saving that much power since that should be
short-lived so Im not sure we should bother with it.

--=20
Luiz Augusto von Dentz