linux-bluetooth.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Luiz Augusto von Dentz <luiz.dentz@gmail.com>
To: chethan tn <chethantn@gmail.com>
Cc: Bluez mailing list <linux-bluetooth@vger.kernel.org>,
	Chethan T N <chethan.tumkur.narayan@intel.com>,
	Sathish N <nsathish41@gmail.com>,
	Sathish Narasimman <sathish.narasimman@intel.com>
Subject: Re: L2CAP mtu preference set by user space clarification
Date: Tue, 17 Dec 2019 16:19:06 -0800	[thread overview]
Message-ID: <CABBYNZLW7qe8ie-FLYaka7wKTeKAmBQYf0DG0ZZqbOu2eEOxPA@mail.gmail.com> (raw)
In-Reply-To: <CAMH2TCooGyxiZbhersOCFMHLpjSAqKFq2_XswXx3nt200L-qBQ@mail.gmail.com>

Hi Chethan,

On Mon, Dec 16, 2019 at 10:40 PM chethan tn <chethantn@gmail.com> wrote:
>
> Hi,
>
> I would like to understand why the Source device L2CAP mtu is always
> set to the remote device mtu during L2CAP connection?
>
> https://git.kernel.org/pub/scm/linux/kernel/git/bluetooth/bluetooth.git/tree/net/bluetooth/l2cap_core.c#n3370
> https://git.kernel.org/pub/scm/linux/kernel/git/bluetooth/bluetooth.git/tree/net/bluetooth/l2cap_core.c#n3474
>
>
>
> I tried to set the specific MTU for specific profile connection( For
> Ex: A2DP connection - PSM  25) patch mentioned below, but the same is
> not reflected because of the below code.
>
> https://git.kernel.org/pub/scm/linux/kernel/git/bluetooth/bluetooth.git/tree/net/bluetooth/l2cap_core.c#n3474

The answer is pretty simple, we don't control the remote/output MTU,
so we cannot force the remote to use some arbitrary MTU if it doesn't
agree with.

> Here the patch to set the MTU from the use space bluez.
>
> diff --git a/profiles/audio/a2dp.c b/profiles/audio/a2dp.c
> index 58e1534a4..7d8a718c0 100644
> --- a/profiles/audio/a2dp.c
> +++ b/profiles/audio/a2dp.c
> @@ -1573,6 +1573,7 @@ static bool a2dp_server_listen(struct a2dp_server *server)
>                                 BT_IO_OPT_SOURCE_BDADDR,
>                                 btd_adapter_get_address(server->adapter),
>                                 BT_IO_OPT_PSM, AVDTP_PSM,
> +                               BT_IO_OPT_OMTU, AVDTP_MTU,
>                                 BT_IO_OPT_SEC_LEVEL, BT_IO_SEC_MEDIUM,
>                                 BT_IO_OPT_MASTER, true,
>                                 BT_IO_OPT_INVALID);
> diff --git a/profiles/audio/avdtp.c b/profiles/audio/avdtp.c
> index 51ead684a..786702cec 100644
> --- a/profiles/audio/avdtp.c
> +++ b/profiles/audio/avdtp.c
> @@ -2394,6 +2394,7 @@ static GIOChannel *l2cap_connect(struct avdtp *session)
>                                 BT_IO_OPT_DEST_BDADDR,
>                                 device_get_address(session->device),
>                                 BT_IO_OPT_PSM, AVDTP_PSM,
> +                               BT_IO_OPT_OMTU, AVDTP_MTU,
>                                 BT_IO_OPT_SEC_LEVEL, BT_IO_SEC_MEDIUM,
>                                 BT_IO_OPT_INVALID);
>         if (!io) {
> diff --git a/profiles/audio/avdtp.h b/profiles/audio/avdtp.h
> index 621a6e3cf..372b2579d 100644
> --- a/profiles/audio/avdtp.h
> +++ b/profiles/audio/avdtp.h
>
>
>
> Can you please suggest what is the best way to set the L2CAP mtu as
> user defined.
>
>
> Thanks
>
> Chethan



-- 
Luiz Augusto von Dentz

  reply	other threads:[~2019-12-18  0:19 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-17  6:36 L2CAP mtu preference set by user space clarification chethan tn
2019-12-18  0:19 ` Luiz Augusto von Dentz [this message]
2020-01-28  7:01   ` Sathish Narasimman
2020-01-30  5:19     ` Sathish Narasimman
2020-01-30 19:12     ` Luiz Augusto von Dentz
2020-01-31  5:07       ` Sathish Narasimman

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=CABBYNZLW7qe8ie-FLYaka7wKTeKAmBQYf0DG0ZZqbOu2eEOxPA@mail.gmail.com \
    --to=luiz.dentz@gmail.com \
    --cc=chethan.tumkur.narayan@intel.com \
    --cc=chethantn@gmail.com \
    --cc=linux-bluetooth@vger.kernel.org \
    --cc=nsathish41@gmail.com \
    --cc=sathish.narasimman@intel.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).