From 59bb7f0eebe69aa32a5c7917a23a7da1c5667d73 Mon Sep 17 00:00:00 2001 From: Takashi Iwai Date: Thu, 28 Apr 2011 09:58:43 +0200 Subject: [PATCH] ALSA: usb-audio - Don't expose broken dB ranges Some crappy USB-audio devices give broken dB ranges, e.g. both min and max are 0dB. This confuses the volume control that prefers dB expression such as alsactl or PulseAudio. In such a case, it's much better not to expose the broken dB information. Signed-off-by: Takashi Iwai --- sound/usb/mixer.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-) diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c index 5e4775716607..c8c28cd75534 100644 --- a/sound/usb/mixer.c +++ b/sound/usb/mixer.c @@ -1097,11 +1097,13 @@ static void build_feature_ctl(struct mixer_build *state, void *raw_desc, append_ctl_name(kctl, control == UAC_FU_MUTE ? " Switch" : " Volume"); if (control == UAC_FU_VOLUME) { - kctl->tlv.c = mixer_vol_tlv; - kctl->vd[0].access |= - SNDRV_CTL_ELEM_ACCESS_TLV_READ | - SNDRV_CTL_ELEM_ACCESS_TLV_CALLBACK; check_mapped_dB(map, cval); + if (cval->dBmin < cval->dBmax) { + kctl->tlv.c = mixer_vol_tlv; + kctl->vd[0].access |= + SNDRV_CTL_ELEM_ACCESS_TLV_READ | + SNDRV_CTL_ELEM_ACCESS_TLV_CALLBACK; + } } break;