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From:   Luiz Augusto von Dentz <luiz.dentz@gmail.com>
Date:   Wed, 3 Aug 2022 10:00:47 -0700
Message-ID: <CABBYNZ+vJ5UJdz1KH+34QtR8qGj6x4sRp4CDj0Z=vMX0VYPYWg@mail.gmail.com>
Subject: Re: Connection Event Length
To:     Chris Laplante <Chris.Laplante@lairdconnect.com>
Cc:     "linux-bluetooth@vger.kernel.org" <linux-bluetooth@vger.kernel.org>
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Hi Chris,

On Wed, Aug 3, 2022 at 9:28 AM Chris Laplante
<Chris.Laplante@lairdconnect.com> wrote:
>
> Hi,
>
> Can someone tell me if the Connection Event Min and Max lengths can be se=
t in BlueZ? I have a customer using BlueZ and their throughput is less than=
 optimal. It looks like from their sniffer logs that there is a single PDU =
sent every 18.75mS connection interval. Looking at the mgmt-api.txt doc in =
the BlueZ-5.64 release it doesn't seem the conn event length parameters can=
 be changed.
>
> New Connection Parameter Event
> =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=3D
>
>         Event Code:             0x001c
>         Controller Index:       <controller id>
>         Event Parameters:       Store_Hint (1 Octet)
>                                 Param {
>                                         Address (6 Octets)
>                                         Address_Type (1 Octet)
>                                         Min_Connection_Interval (2 Octets=
)
>                                         Max_Connection_Interval (2 Octets=
)
>                                         Connection_Latency (2 Octets)
>                                         Supervision_Timeout (2 Octets)
>                                 }
>
>         This event indicates a new set of connection parameters from
>         a peripheral device.
>
>         The Store_Hint parameter indicates whether the host is expected
>         to store this information persistently or not.
>
>         Possible values for the Address_Type parameter:
>                 0       Reserved (not in use)
>                 1       LE Public
>                 2       LE Random
>
>         The Min_Connection_Interval, Max_Connection_Interval,
>         Connection_Latency and Supervision_Timeout parameters are
>         encoded as described in Core 4.1 spec, Vol 2, 7.7.65.3.
>
> I am a novice BlueZ user so if for one I am not looking in the right plac=
e please point me to where I should be looking for this info. And also if i=
t is supported please could you provide details on how it can be supported.

You can set the preferred parameter via main.conf:

https://git.kernel.org/pub/scm/bluetooth/bluez.git/tree/src/main.conf#n202

That said if the peripheral changes these parameters it might cause
them to stored and in that case that is used instead of the global
ones, btw it looks like some peripherals have started to set very high
values for interval in order to save power, the problem is that the
central has no idea about that and will not restore to the normal
settings once there is any traffic. We might need to start handling
the likes of PPCP characteristic in order to determine exactly what is
the prefered settings and when acting as peripheral we shall set it
based on what is configured over main.conf so the central can tell
what is our preferred settings as well.

> Thank you in advance!
>
> Chris
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--=20
Luiz Augusto von Dentz