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From:   Luiz Augusto von Dentz <luiz.dentz@gmail.com>
Date:   Wed, 9 Mar 2022 13:02:25 -0800
Message-ID: <CABBYNZ+rg+=ZOAFdBFhyE=Ki7KL1C=Jq-w2cT3rMTMmoMTt6_w@mail.gmail.com>
Subject: Re: [RFC] Bluetooth: Adding support for /etc/bluetooth/main.conf.d
To:     Bastien Nocera <hadess@hadess.net>
Cc:     Sonny Sasaka <sonnysasaka@chromium.org>,
        Katherine Lai <laikatherine@chromium.org>,
        BlueZ <linux-bluetooth@vger.kernel.org>
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Hi,

On Wed, Mar 9, 2022 at 12:44 PM Luiz Augusto von Dentz
<luiz.dentz@gmail.com> wrote:
>
> Hi,
>
> On Wed, Mar 9, 2022 at 4:10 AM Bastien Nocera <hadess@hadess.net> wrote:
> >
> > On Tue, 2022-03-08 at 14:50 -0800, Sonny Sasaka wrote:
> > > Hi Bastien,
> > >
> > >
> > > On Tue, Mar 8, 2022 at 2:14 AM Bastien Nocera <hadess@hadess.net>
> > > wrote:
> > > >
> > > > Hey Katherine,
> > > >
> > > > On Mon, 2022-03-07 at 10:57 -0800, Katherine Lai wrote:
> > > > > Background
> > > > >
> > > > > It was found that a change to the default settings for
> > > > > MinConnectionInterval and MaxConnectionInterval in main.conf
> > > > > broke
> > > > > some of ChromeOS=E2=80=99s keyboard HID tests for only certain Bl=
uetooth
> > > > > controllers. These keyboards aren=E2=80=99t able to connect to th=
e
> > > > > device.
> > > > > Since those connection parameters improve the connection interval
> > > > > for
> > > > > most other chipsets, we want to leave the default values but have
> > > > > a
> > > > > way to have an optional override to address problematic models.
> > > > >
> > > > >
> > > > > Proposed Solution
> > > > >
> > > > > Adding support to bluetoothd for an additional config directory
> > > > > /etc/bluetooth/main.conf.d containing multiple files which will
> > > > > override common params. Override order will be lexically sorted
> > > > > filename order. This pattern is already used by Linux distros,
> > > > > for
> > > > > example there is /etc/sudoers.d which files will override common
> > > > > params in /etc/sudoers.
> > > > >
> > > > > Users can add override config files to /etc/bluetooth/main.conf.d
> > > > > rather than directly editing /etc/bluetooth/main.conf. This is
> > > > > more
> > > > > friendly to package managers since BlueZ package updates won't
> > > > > cause
> > > > > conflict to /etc/bluetooth/main.conf.
> > > > >
> > > > > In bluez=E2=80=99s main.c, merge the params for each *.conf file =
from
> > > > > /etc/bluetooth/main.conf.d with the existing
> > > > > /etc/bluetooth/main.conf
> > > > > in lexical filename order
> > > > >
> > > > > /etc/bluetooth/main.conf.d will be configurable at build time,
> > > > > e.g.
> > > > > with ./configure --main-conf-dir
> > > >
> > > > This isn't quite how the pattern is usually used. With the existing
> > > > patterns, the OS-supplied stock configuration would be in
> > > > /usr/lib/bluetooth/main.conf.d (maybe with the default .conf in the
> > > > same directory as that subdir), with /etc/bluetooth/main.conf.d
> > > > only
> > > > used for the user/admin override the default configuration.
> > > We did a bit of research and found that /etc/X and /etc/X.d is more
> > > common, e.g. the one described in
> > > https://www.redhat.com/sysadmin/etc-configuration-directories.
> >
> > This is documentation for an enterprise distribution, not how the
> > pattern is now used upstream.
> >
> > $ ls -d1 /usr/lib/*.d/
> > /usr/lib/binfmt.d/
> > /usr/lib/environment.d/
> > /usr/lib/modprobe.d/
> > /usr/lib/modules-load.d/
> > /usr/lib/motd.d/
> > /usr/lib/pam.d/
> > /usr/lib/sysctl.d/
> > /usr/lib/sysusers.d/
> > /usr/lib/tmpfiles.d/
> > $ ls -d1 /usr/lib/*/*.d/
> > /usr/lib/dracut/dracut.conf.d/
> > /usr/lib/dracut/modules.d/
> > /usr/lib/fedora-third-party/conf.d/
> > /usr/lib/gconv/gconv-modules.d/
> > /usr/lib/kernel/install.d/
> > /usr/lib/NetworkManager/conf.d/
> > /usr/lib/NetworkManager/dispatcher.d/
> > /usr/lib/rpm/macros.d/
> > /usr/lib/systemd/ntp-units.d/
> > /usr/lib/udev/hwdb.d/
> > /usr/lib/udev/rules.d/
> >
> > > If some distribution wants to organize the conf files to
> > > /usr/lib/bluetooth (for stock by package managers) and
> > > /etc/bluetooth/main.conf.d (for admin/users), I guess this is where
> > > having a configurable path is useful.
> > > What do you think?
> >
> > I'm saying this isn't the current pattern, especially for OSes where
> > /usr is locked-down. I still think this isn't the right way to
> > implement this feature.
>
> Before we start doing this we should check if the devices with
> problems don't implement Peripheral Preferred Connection Parameters
> (PPCP) as some of peripherals are not capable of updating the
> connection parameters themselves they depend on the central reading
> the PPCP, some years back we got someone attempting to implement PPCP
> support but the problem was that one needs to load all the devices
> connection parameters with Peripheral Preferred Connection Parameters
> management command, anyway it would be great to have support for PPCP
> even if that means reloading everything or perhaps we introduce
> something at socket level where the user can set the parameters which
> then gets saved once the update connection parameters procedure is
> completed.

Here it is the RFC for the kernel side:

https://www.spinics.net/lists/linux-bluetooth/msg69520.html

It probably needs some improvements like checkinf if the conneciton is
really LE, etc.

> --
> Luiz Augusto von Dentz


--=20
Luiz Augusto von Dentz