@dragu I'll give it a go on a pi3, but still, it does work for me
my (filtered) lsmod reports :
Module Size Used by Not tainted
snd_soc_hifiberry_dacplus 4100 1
snd_soc_pcm512x_i2c 2243 1
snd_soc_hifiberry_dac 2511 0
snd_soc_bcm2835_i2s 6354 2
snd_soc_pcm512x 17268 1 snd_soc_pcm512x_i2c
snd_soc_core 125885 4 snd_soc_hifiberry_dacplus,snd_soc_hifiberry_dac,snd_soc_bcm2835_i2s,snd_soc_pcm512x
regmap_i2c 3393 1 snd_soc_pcm512x_i2c
snd_pcm_dmaengine 3391 1 snd_soc_core
snd_pcm 75698 7 snd_bcm2835,snd_soc_hifiberry_dacplus,snd_soc_hifiberry_dac,snd_soc_pcm512x,snd_soc_core,snd_pcm_dmaengine
snd_timer 19156 1 snd_pcm
snd 51908 5 snd_bcm2835,snd_soc_core,snd_pcm,snd_timer
clk_hifiberry_dacpro 2278 1
uio 8000 1 uio_pdrv_genirq