Using AVIRT =================================== ## Introduction ## Table of Contents 1. [Load/Unload AVIRT](#un-load-avirt) 2. [Configuring AVIRT](#configuring-avirt) ## Loading and Unloading AVIRT ### Load Out of Tree As root, load the required `avirt_core.ko` and subsequent audio path. As an example, the Dummy Audiopath is being loaded here. ```sh insmod snd-avirt-core.ko insmod dummy/snd-avirt-ap-dummy.ko insmod loopback/snd-avirt-ap-loopback.ko ``` ### Note: The loading and unloading of drivers can be performed using the helper scripts. To run, we must load the kernel modules using the `scripts/load.sh` script: ```sh $ ./scripts/load.sh ``` To unload the drivers use: ```sh $ ./scripts/unload.sh ``` ### Load In Tree #### Note: Either build the module in tree, or you can copy the modules manually and then run `depmod` to generate dependencies. For example, in AGL: ```sh mkdir -p /lib/modules/$(uname -r)/extra cp snd-avirt-core.ko snd-avirt-ap-dummy.ko snd-avirt-ap-loopback.ko /lib/modules/$(uname -r)/extra depmod ``` Once the modules are in place, we can load the modules using: ```sh modprobe snd-avirt-core modprobe snd-avirt-ap-dummy modprobe snd-avirt-ap-loopback ``` ## Configuring AVIRT AVIRT is configured using configfs. ### Note: A sample script for the following is supplied inside the `scripts` folder. First, verify the kernel supports the use of configfs. ```sh fgrep configfs /proc/filesystems ``` The expected output is: ``` nodev configfs ``` Once confirmed, we can mount the `configfs` filesystem at the conventional point: ```sh # Check configfs is mounted on the system mkdir -p /config mount -t configfs none /config ``` Finally, we can configure AVIRT, for example: ```sh # Set up each of the cards channels mkdir /config/snd-avirt/streams/playback_media echo "2">/config/snd-avirt/streams/playback_media/channels echo "ap_dummy">/config/snd-avirt/streams/playback_media/map mkdir /config/snd-avirt/streams/playback_navigation echo "1">/config/snd-avirt/streams/playback_navigation/channels echo "ap_dummy">/config/snd-avirt/streams/playback_navigation/map mkdir /config/snd-avirt/streams/playback_emergency echo "1">/config/snd-avirt/streams/playback_emergency/channels echo "ap_dummy">/config/snd-avirt/streams/playback_emergency/map mkdir /config/snd-avirt/streams/capture_voice echo "1">/config/snd-avirt/streams/capture_voice/channels echo "ap_dummy">/config/snd-avirt/streams/capture_voice/map # Finally, seal the card, and initiate configuration echo "1">/config/snd-avirt/streams/sealed ``` Alternatively, the test script at `scripts/test_configfs.sh` can be used. The user-space library, [libavirt](https://github.com/fiberdyne/libavirt) can be used to interact with the configfs interface. Please refer to the README in libavirt for further details. ## 3. Checking AVIRT Loaded Correctly We can see the newly created streams by using the `aplay` utility. For example, the device list might look a little like this: ```sh aplay -l ... card 2: avirt [avirt], device 0: multimedia [multimedia] Subdevices: 1/1 Subdevice #0: subdevice #0 card 2: avirt [avirt], device 1: navigation [navigation] Subdevices: 1/1 Subdevice #0: subdevice #0 card 2: avirt [avirt], device 2: emergency [emergency] Subdevices: 1/1 Subdevice #0: subdevice #0 ... ```