Se comment in patch: a5c7d797dcce3be5e77cd6ea62cc4920ededc32b ALSA: usb-audio - Add volume resolution quirk for some Logitech webcams
Signed-off-by: Alexey Fisher bug-track@fisher-privat.net --- sound/usb/mixer.c | 15 +++++++++++++++ 1 files changed, 15 insertions(+), 0 deletions(-)
diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c index 85af605..eba8ae8 100644 --- a/sound/usb/mixer.c +++ b/sound/usb/mixer.c @@ -987,6 +987,7 @@ static void build_feature_ctl(struct mixer_build *state, void *raw_desc, struct snd_kcontrol *kctl; struct usb_mixer_elem_info *cval; const struct usbmix_name_map *map; + unsigned int range;
control++; /* change from zero-based to 1-based value */
@@ -1136,6 +1137,20 @@ static void build_feature_ctl(struct mixer_build *state, void *raw_desc,
}
+ range = (cval->max - cval->min) / cval->res; + /* Are there devices with volume range more than 255? I use a bit more + * to be sure. 384 is a resolution magick nuber found on Logitech + * devices. It will definitively catch all buggy Logitech devices. */ + if (range > 384) { + snd_printk(KERN_WARNING "usb_audio: Warning! Unlikely big " + "volume range (=%u), cval->res is probably wrong.", + range); + snd_printk(KERN_WARNING "usb_audio: [%d] FU [%s] ch = %d, " + "val = %d/%d/%d", cval->id, + kctl->id.name, cval->channels, + cval->min, cval->max, cval->res); + } + snd_printdd(KERN_INFO "[%d] FU [%s] ch = %d, val = %d/%d/%d\n", cval->id, kctl->id.name, cval->channels, cval->min, cval->max, cval->res); add_control_to_empty(state, kctl);