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From:   Katherine Lai <laikatherine@chromium.org>
Date:   Mon, 7 Mar 2022 10:57:02 -0800
Message-ID: <CAPBVwTQrcYYauoCXBWdOsPa_vmN=cajYzVFcep_GLC-2OwOwYQ@mail.gmail.com>
Subject: [RFC] Bluetooth: Adding support for /etc/bluetooth/main.conf.d
To:     linux-bluetooth@vger.kernel.org
Cc:     Sonny Sasaka <sonnysasaka@chromium.org>
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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 Bluetooth
controllers. These keyboards aren=E2=80=99t 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=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