miropcm20 uses ALSA (snd_) interfaces from the SND_MIRO
driver, so it should depend on SND.
(selecting SND_MIRO when CONFIG_SND is not enabled is a
problem.)
drivers/built-in.o: In function `vidioc_s_ctrl':
radio-miropcm20.c:(.text+0x227499): undefined reference to `snd_aci_cmd'
drivers/built-in.o: In function `vidioc_s_frequency':
radio-miropcm20.c:(.text+0x227574): undefined reference to `snd_aci_cmd'
radio-miropcm20.c:(.text+0x227588): undefined reference to `snd_aci_cmd'
drivers/built-in.o: In function `pcm20_init':
radio-miropcm20.c:(.init.text+0x2a784): undefined reference to `snd_aci_get_aci'
miropcm20 selects SND_MIRO but SND_ISA may be not enabled, so
also select SND_ISA so that the snd-miro driver will be built.
Otherwise there are missing symbols: