Received-SPF: pass (google.com: domain of linux-bluetooth-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <6f8f47ceebfbcfd7fa8b04a4df807ae822e2960c.camel@hadess.net>
Subject: Re: [RFC] Bluetooth: Adding support for /etc/bluetooth/main.conf.d
From:   Bastien Nocera <hadess@hadess.net>
To:     Katherine Lai <laikatherine@chromium.org>,
        linux-bluetooth@vger.kernel.org
Cc:     Sonny Sasaka <sonnysasaka@chromium.org>
Date:   Tue, 08 Mar 2022 11:14:52 +0100
In-Reply-To: <CAPBVwTQrcYYauoCXBWdOsPa_vmN=cajYzVFcep_GLC-2OwOwYQ@mail.gmail.com>
References: <CAPBVwTQrcYYauoCXBWdOsPa_vmN=cajYzVFcep_GLC-2OwOwYQ@mail.gmail.com>
Content-Type: text/plain; charset="UTF-8"
User-Agent: Evolution 3.42.4 (3.42.4-1.fc35) 
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

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’s keyboard HID tests for only certain Bluetooth
> controllers. These keyboards aren’t able to connect to the 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’s 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.

I don't think that making it optional, or have the path changeable is
needed, but the rest seems good.

Cheers