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[ALSA] Test volume resolution of usb audio at initialization

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Test the volume of usb audio whether actually it works and adjusts
the resolution value according to it.

Some USB audio devices report a lower resolution than it reacts.
The only possible check is to write and read a volume value.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Takashi Iwai 2006-03-28 17:58:28 +02:00 committed by Jaroslav Kysela
parent 0b2dcd5d6a
commit 14790f1c73
1 changed files with 34 additions and 3 deletions
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37
sound/usb/usbmixer.c
View file

@ -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;
}