Hi,

Summary of this message: * systemd got udev rules with new database for firewire node/unit * then fw character device for audio is owned by 'audio' group with ACL * the entries are added by my investigation, thus doesn't cover all * if you have firewire audio devices not listed in README of below repository, please contact to me with image of configuration ROM: * https://github.com/takaswie/am-config-roms/

The way to create image file of configuration ROM is typically:

``` $ cat /sys/bus/firewire/devices/fw1/config_rom > filename.img ```

Here, I presuppose that Linux FireWire subsystem detects your device as 'fw1'.

Well, in the past, access permission of Linux firewire character device is decided by udev rules just for video devices[1]. This was inconvenient some project such as ALSA and FFADO to produce audio application.

The source code of libffado includes own file for udev rules[2] to take firewire character device owned by 'audio' group. Additionally the rules gives 'ID_FFADO' tag, and systemd includes another udev rule[3] to ACL at logging-in time according to it.

As a whole, the above is not comprehensive and self-contained. I proposed patchset to systemd for better solution and today it was merged. * https://github.com/systemd/systemd/pull/19124

In the patchset, I add some udev rules, based on hwdb for new entries of node and units in IEEE 1394 bus. You can see the database[4].

The entries of database have below variables when matching to either node or unit devices: * IEEE1394_UNIT_FUNCTION_MIDI * IEEE1394_UNIT_FUNCTION_AUDIO * IEEE1394_UNIT_FUNCTION_VIDEO

The added udev rules interpret the content of variables and decide group owner of fw character device(see [1]). Furthermore, the variables are used again to decide ACL in logging-in time(see [3], too).

The entries of database also include below variables: * ID_VENDOR_FROM_DATABASE * ID_MODEL_FROM_DATABASE

They are expected to use applications such as PipeWire and PulseAudio for better names of sound device, which binds to unit instead of node. I expect the variables can obsolete my former patch for pulseaudio[5].

I handy write the entries of database from my investigation, thus it could includes the lack of your device, or mistakes. I wish you to contact to me with image file of configuration ROM when you can not find your device in README of my collection repository[6], or when you find any mistakes in database file.

Thanks for your cooperation in advance.

[1] 4 rules in 'rules.d/50-udev-default.rules' https://github.com/systemd/systemd/blob/main/rules.d/50-udev-default.rules.i... [2] many rules in 'libffado/60-ffado.rules' http://subversion.ffado.org/browser/trunk/libffado/libffado/60-ffado.rules?r... [3] 'src/login/70-uaccess.rules.m4' https://github.com/systemd/systemd/blob/main/src/login/70-uaccess.rules.m4 [4] 'hwdb.d/80-ieee1394-unit-function.hwdb' https://github.com/systemd/systemd/blob/main/hwdb.d/80-ieee1394-unit-functio... [5] udev: use ID_MODEL/ID_VENDOR to give friendly name for FireWire devices https://gitlab.freedesktop.org/pulseaudio/pulseaudio/-/commit/3ac73598c67c [6] https://github.com/takaswie/am-config-roms/

Takashi Sakamoto