[alsa-devel] A question about speaker volume control of Creative Recon3D

Hello All, Recently I looked into the hda code for Creative sound cards, based on linux-3.6-rc3. I found that for Ca0110 (X-Fi), the patch (Patch_ca0110.c) would call add_out_volume() (and add_mono_volume()) for those DACs (refer to the ca0110_build_controls() function). While for ca0132 (Recon3D), its patch (Patch_ca0132.c) does not call add_out_volume() for any DAC (refer to the ca0132_build_controls() function). If I play a wav file under Ubuntu, it can adjust the speaker volume successfully with the Recon3D card. Can somebody kindly tell me how the speaker volume been controlled for this card? Thanks, Ming