}
 
        switch (protocol) {
+       default:
+               snd_printdd(KERN_WARNING "unknown interface protocol %#02x, assuming v1\n",
+                           protocol);
+               /* fall through */
+
        case UAC_VERSION_1: {
                struct uac1_ac_header_descriptor *h1 = control_header;
 
 
                break;
        }
-
-       default:
-               snd_printk(KERN_ERR "unknown protocol version 0x%02x\n", protocol);
-               return -EINVAL;
        }
 
        return 0;
 
 
        switch (altsd->bInterfaceProtocol) {
        case UAC_VERSION_1:
+       default:
                return set_sample_rate_v1(chip, iface, alts, fmt, rate);
 
        case UAC_VERSION_2:
                return set_sample_rate_v2(chip, iface, alts, fmt, rate);
        }
-
-       return -EINVAL;
 }
 
 
 
                /* get audio formats */
                switch (protocol) {
+               default:
+                       snd_printdd(KERN_WARNING "%d:%u:%d: unknown interface protocol %#02x, assuming v1\n",
+                                   dev->devnum, iface_no, altno, protocol);
+                       protocol = UAC_VERSION_1;
+                       /* fall through */
+
                case UAC_VERSION_1: {
                        struct uac1_as_header_descriptor *as =
                                snd_usb_find_csint_desc(alts->extra, alts->extralen, NULL, UAC_AS_GENERAL);
                                   dev->devnum, iface_no, altno, as->bTerminalLink);
                        continue;
                }
-
-               default:
-                       snd_printk(KERN_ERR "%d:%u:%d : unknown interface protocol %04x\n",
-                                  dev->devnum, iface_no, altno, protocol);
-                       continue;
                }
 
                /* get format type */
 
        u64 pcm_formats;
 
        switch (protocol) {
-       case UAC_VERSION_1: {
+       case UAC_VERSION_1:
+       default: {
                struct uac_format_type_i_discrete_descriptor *fmt = _fmt;
                sample_width = fmt->bBitResolution;
                sample_bytes = fmt->bSubframeSize;
                format <<= 1;
                break;
        }
-
-       default:
-               return -EINVAL;
        }
 
        pcm_formats = 0;
         * audio class v2 uses class specific EP0 range requests for that.
         */
        switch (protocol) {
+       default:
+               snd_printdd(KERN_WARNING "%d:%u:%d : invalid protocol version %d, assuming v1\n",
+                          chip->dev->devnum, fp->iface, fp->altsetting, protocol);
+               /* fall through */
        case UAC_VERSION_1:
                fp->channels = fmt->bNrChannels;
                ret = parse_audio_format_rates_v1(chip, fp, (unsigned char *) fmt, 7);
                /* fp->channels is already set in this case */
                ret = parse_audio_format_rates_v2(chip, fp);
                break;
-       default:
-               snd_printk(KERN_ERR "%d:%u:%d : invalid protocol version %d\n",
-                          chip->dev->devnum, fp->iface, fp->altsetting, protocol);
-               return -EINVAL;
        }
 
        if (fp->channels < 1) {
        fp->channels = 1;
 
        switch (protocol) {
+       default:
+               snd_printdd(KERN_WARNING "%d:%u:%d : invalid protocol version %d, assuming v1\n",
+                          chip->dev->devnum, fp->iface, fp->altsetting, protocol);
+               /* fall through */
        case UAC_VERSION_1: {
                struct uac_format_type_ii_discrete_descriptor *fmt = _fmt;
                brate = le16_to_cpu(fmt->wMaxBitRate);
                ret = parse_audio_format_rates_v2(chip, fp);
                break;
        }
-       default:
-               snd_printk(KERN_ERR "%d:%u:%d : invalid protocol version %d\n",
-                          chip->dev->devnum, fp->iface, fp->altsetting, protocol);
-               return -EINVAL;
        }
 
        return ret;
 
        }
 
        host_iface = &usb_ifnum_to_if(chip->dev, ctrlif)->altsetting[0];
-       mixer->protocol = get_iface_desc(host_iface)->bInterfaceProtocol;
+       switch (get_iface_desc(host_iface)->bInterfaceProtocol) {
+       case UAC_VERSION_1:
+       default:
+               mixer->protocol = UAC_VERSION_1;
+               break;
+       case UAC_VERSION_2:
+               mixer->protocol = UAC_VERSION_2;
+               break;
+       }
 
        if ((err = snd_usb_mixer_controls(mixer)) < 0 ||
            (err = snd_usb_mixer_status_create(mixer)) < 0)
 
 
        switch (altsd->bInterfaceProtocol) {
        case UAC_VERSION_1:
+       default:
                return init_pitch_v1(chip, iface, alts, fmt);
 
        case UAC_VERSION_2:
                return init_pitch_v2(chip, iface, alts, fmt);
        }
-
-       return -EINVAL;
 }
 
 /*