1 files changed, 34 insertions, 3 deletions

diff --git a/sound/usb/usbmixer.c b/sound/usb/usbmixer.c
index 8d08b34a1cb5..ce86283ee0fa 100644
--- a/sound/usb/usbmixer.c
+++ b/sound/usb/usbmixer.c
@@ -306,8 +306,8 @@ static int get_relative_value(struct usb_mixer_elem_info *cval, int val)
                 cval->res = 1;
         if (val < cval->min)
                 return 0;
-        else if (val > cval->max)
-                return (cval->max - cval->min) / cval->res;
+        else if (val >= cval->max)
+                return (cval->max - cval->min + cval->res - 1) / cval->res;
         else
                 return (val - cval->min) / cval->res;
 }
@@ -670,6 +670,36 @@ static int get_min_max(struct usb_mixer_elem_info *cval, int default_min)
                 }
                 if (cval->res == 0)
                         cval->res = 1;
+
+                /* Additional checks for the proper resolution
+                 *
+                 * Some devices report smaller resolutions than actually
+                 * reacting.  They don't return errors but simply clip
+                 * to the lower aligned value.
+                 */
+                if (cval->min + cval->res < cval->max) {
+                        int last_valid_res = cval->res;
+                        int saved, test, check;
+                        get_cur_mix_value(cval, minchn, &saved);
+                        for (;;) {
+                                test = saved;
+                                if (test < cval->max)
+                                        test += cval->res;
+                                else
+                                        test -= cval->res;
+                                if (test < cval->min || test > cval->max ||
+                                    set_cur_mix_value(cval, minchn, test) ||
+                                    get_cur_mix_value(cval, minchn, &check)) {
+                                        cval->res = last_valid_res;
+                                        break;
+                                }
+                                if (test == check)
+                                        break;
+                                cval->res *= 2;
+                        }
+                        set_cur_mix_value(cval, minchn, saved);
+                }
+
                 cval->initialized = 1;
         }
         return 0;
@@ -695,7 +725,8 @@ static int mixer_ctl_feature_info(struct snd_kcontrol *kcontrol, struct snd_ctl_
                 if (! cval->initialized)
                         get_min_max(cval,  0);
                 uinfo->value.integer.min = 0;
-                uinfo->value.integer.max = (cval->max - cval->min) / cval->res;
+                uinfo->value.integer.max =
+                        (cval->max - cval->min + cval->res - 1) / cval->res;
         }
         return 0;
 }