Get the audio output level of a given audio device.
#include <audio/audio_manager_volume.h>
int audio_manager_get_output_level(audio_manager_device_t dev, double *level)
The audio device to query.
The output level being returned in percentage, 0.00 - 100.0 (e.g. 90.00 = 90%).
The audio_manager_get_output_level() function returns the audio output level of a given audio device.
EOK upon success, negative errno upon failure.