rtcirqus 0.1.1

Set real-time priorities of IRQ threads dynamically

Introduction

rtcirqus, real-time config IRQ udev service, is a Python script that sets the real-time priority of IRQ threads of onboard and USB audio interfaces automatically using udev. It is heavily inspired by Joakim Hernberg’s udev-rtirq project.

Features

• Automatic real-time prioritization of onboard audio devices

• Automatic real-time prioritization of USB audio devices upon connection and disconnection

Installation

rtcirqus needs at least Python 3.6 and the following Python modules:

• pyalsaaudio

• psutil

• pyudev

On a Debian 12 system these modules can be installed with apt install python3-alsaaudio python3-psutil python3-pyudev

Clone this repository:

git clone https://codeberg.org/autostatic/rtcirqus.git

Copy src/rtcirqus/rtcirqus.py to /usr/local/bin/rtcirqus:

sudo cp src/rtcirqus/rtcirqus.py /usr/local/bin/rtcirqus
sudo chmod 755 /usr/local/bin/rtcirqus

Copy resources/99-rtcirqus.rules to /etc/udev/rules.d/:

sudo cp resources/99-rtcirqus.rules /etc/udev/rules.d/

And reload the udev rules:

sudo udevadm control --reload-rules

Optionally you could copy rtcirqus.conf to /etc/rtcirqus.d/rtcirqus.conf:

sudo mkdir /etc/rtcirqus.d/
sudo cp resources/rtcirqus.conf /etc/rtcirqus.d/conf

And modify it to your needs. So far only the deny_list option is available. This option takes a comma separated list of card names as produced by rtcirqus itself or by aplay -l. In the case of aplay -l the card names are the names between the brackets.

Installation in a Virtual Environment

To install the rtcirqus project in a Python virtual environment for development:

cd /path/to/clone/of/rtcirqus
python3.9 -m venv /path/to/venv  # Python >= 3.9
/path/to/venv/bin/pip install -e .

pip will install the dependencies, and create a script, rtcirqus in its bin/ directory, which you can run directly:

/path/to/venv/bin/rtcirqus --help

You can then copy that script to /usr/local/bin/rtcirqus:

sudo cp /path/to/venv/bin/rtcirqus /usr/local/bin/

and proceed as above, adding udev rules and copying / updating configuration.

Overview

You can now check if rtcirqus works properly by running it as a normal user. It will produce output similar to the following:

$ rtcirqus
WARNING: No configuration file found, continuing with defaults
INFO: Loaded kernel is using threaded IRQS and threaded IRQ processes detected
INFO: Onboard cards found: HD-Audio Generic, HD-Audio Generic, acp63
INFO: USB cards found: Babyface (23596862)
ERROR: Not running as root, rtcirqus needs to be run as root in order to set IRQ priorities

You can check if rtcirqus gets triggered by udev by plugging in a USB device while running sudo journalctl -f. You should see something in the lines of:

Feb 16 22:34:10 lenovo kernel: usb 7-1: new high-speed USB device number 10 using xhci_hcd
Feb 16 22:34:11 lenovo kernel: usb 7-1: New USB device found, idVendor=0424, idProduct=3fb7, bcdDevice= 0.01
Feb 16 22:34:11 lenovo kernel: usb 7-1: New USB device strings: Mfr=1, Product=2, SerialNumber=3
Feb 16 22:34:11 lenovo kernel: usb 7-1: Product: Babyface (23596862)
Feb 16 22:34:11 lenovo kernel: usb 7-1: Manufacturer: RME
Feb 16 22:34:11 lenovo kernel: usb 7-1: SerialNumber: 18C0A73560538C8
Feb 16 22:34:11 lenovo kernel: usb 7-1: Quirk or no altest; falling back to MIDI 1.0
Feb 16 22:34:11 lenovo mtp-probe[15199]: checking bus 7, device 10: "/sys/devices/pci0000:00/0000:00:08.3/0000:66:00.4/usb7/7-1"
Feb 16 22:34:11 lenovo mtp-probe[15199]: bus: 7, device: 10 was not an MTP device
Feb 16 22:34:11 lenovo systemd[1]: Started run-r4c9e3d2d062846ecab03c6af31529349.service - /usr/local/bin/rtcirqus --action add --dev-path /devices/pci0000:00/0000:00:08.3/0000:66:00.4/usb7/7-1/7-1:1.0/sound/card0.
Feb 16 22:34:11 lenovo mtp-probe[15216]: checking bus 7, device 10: "/sys/devices/pci0000:00/0000:00:08.3/0000:66:00.4/usb7/7-1"
Feb 16 22:34:11 lenovo mtp-probe[15216]: bus: 7, device: 10 was not an MTP device
Feb 16 22:34:11 lenovo rtcirqus[15212]: WARNING: No configuration file found, continuing with defaults
Feb 16 22:34:11 lenovo rtcirqus[15212]: INFO: Loaded kernel is using threaded IRQs and threaded IRQ processes detected
Feb 16 22:34:11 lenovo rtcirqus[15212]: INFO: Onboard cards found: HD-Audio Generic, HD-Audio Generic, acp63
Feb 16 22:34:11 lenovo rtcirqus[15212]: INFO: USB cards found: Babyface (23596862)
Feb 16 22:34:11 lenovo rtcirqus[15212]: INFO: Setting RT priority 90 for USB card Babyface (23596862)
Feb 16 22:34:11 lenovo rtcirqus[15212]: INFO: Setting RT priority 85 for onboard card HD-Audio Generic
Feb 16 22:34:11 lenovo rtcirqus[15212]: INFO: Setting RT priority 80 for onboard card HD-Audio Generic
Feb 16 22:34:11 lenovo systemd[1]: run-r4c9e3d2d062846ecab03c6af31529349.service: Deactivated successfully.

Future plans

• Allow custom ordering of devices

• Improve handling of USB devices connected to USB2 ports using the ehci_hcd kernel module

• Add option to choose between static mode and dynamic mode

  • static mode: priorities of connected devices stay the same upon connection or disconnection of devices

  • dynamic mode: priorities of connected devices get reinitialized upon connection or disconnection of devices

• Think of a logo

Contact

To contact me send me a mail or if it’s a technical issue or question, use the project’s issue tracker at codeberg.org .