Title says it all. The approach in question is the RNAV 17 at KMPV. The approach has an LPV DA, an LNAV/VNAV DA that is about 100 feet higher, and an LNAV MDA that is higher still. The LPV DA is NA by NOTAM due to trees close to the airport perimeter, evidently affecting clearance on the missed. Therefore, when flying this approach with a WAAS GPS (in my case, a CNX-80 (aka GNS-480)), the unit will annunciate LPV. According to one opinion, claimed to be based on 91.175 (b), you are legally flying whatever the unit annunciates. Since the LPV DA is NA, you cannot fly the approach to that DA, but also, you cannot fly to the LNAV/VNAV DA since the unit will not annunciate LNAV/VNAV under these circumstances (WAAS GPS and no Baro-VNAV). In one version of this opinion, you can still fly to the LNAV MDA even with the unit annunciating LPV. In another, you cannot even do that unless you turn WAAS off to force annunciation of LNAV. Another opinion says that you can fly to any higher DA or MDA that is still authorized. I have no idea which opinion is correct. As a matter of safety, I should think the last opinion is correct unless the LNAV/VNAV glide path is different from that of the LPV approach. In particular, I'm hoping that @John Collins will weigh in on this.