[alsa-devel] How to implement capture_switch control?

Hello list,

I have a device with wm8903 codec. To support mute/unmute capture signal, I was trying to enable/disable PGA on this codec from user space application like

snd_ctl_elem_value_set_boolean("Left Input PGA Switch", 0, 0)

That means the mute/unmute function became platform dependent. I got the idea to support mute/unmute function with enabling/disabling capture switch. However, the function

snd_mixer_selem_has_capture_switch()

alwasy return false. I guess something is missing in my driver. Could you please give some bright how could I use capture switch to mute/unmute a channel. How could I implement capture_switch control properly? Thank you!

/Adam