4b烧入ubuntu 20.04 64位镜像 接上DAC红灯亮
系统里面找不到音频设备
是需要安装额外的驱动吗
```
ubuntu@ubuntu:~$ uname -a
Linux ubuntu 5.4.0-1011-raspi #11-Ubuntu SMP Fri May 8 07:43:33 UTC 2020 aarch64 aarch64 aarch64 GNU/Linux
ubuntu@ubuntu:~$ cat /boot/firmware/syscfg.txt
# This file is intended to be modified by the pibootctl utility. User
# configuration changes should be placed in "usercfg.txt". Please refer to the
# README file for a description of the various configuration files on the boot
# partition.

enable_uart=1
dtparam=audio=on
dtparam=i2c_arm=on
dtparam=spi=on
cmdline=cmdline.txt
ubuntu@ubuntu:~$ cat /boot/firmware/usercfg.txt
# Place "config.txt" changes (dtparam, dtoverlay, disable_overscan, etc.) in
# this file. Please refer to the README file for a description of the various
# configuration files on the boot partition.
dtparam=audio=on
ubuntu@ubuntu:~$ aplay -L
null
Discard all samples (playback) or generate zero samples (capture)
ubuntu@ubuntu:~$ aplay -l
aplay: device_list:274: no soundcards found...
ubuntu@ubuntu:~$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 20.04 LTS
Release: 20.04
Codename: focal
```