Hi, 17.08.2015, 17:16, Takashi Iwai kirjoitti: > On Sun, 16 Aug 2015 14:50:12 +0200, > Anssi Hannula wrote: >> >> AudioQuest DragonFly DAC reports a volume control range of 0..50 >> (0x0000..0x0032) which in USB Audio means a range of 0 .. 0.2dB, which >> is obviously incorrect and causes software using the dB information in >> e.g. volume sliders to have a massive volume difference in 100..102% >> range. >> >> The actual volume mapping seems to be neither linear volume nor linear >> dB scale, but instead quite close to the cubic mapping e.g. alsamixer >> uses, with a range of -53...0 dB. >> >> Add a quirk for DragonFly to use a custom dB mapping, based on my >> measurements, using a 10-item range TLV (so it still fits in alsa-lib >> MAX_TLV_RANGE_SIZE). >> >> Tested on AudioQuest DragonFly HW v1.2. The quirk is only applied if the >> range is 0..50, so if this gets fixed/changed in later HW revisions it >> will no longer be applied. >> >> Signed-off-by: Anssi Hannula <anssi.hann...@iki.fi> >> Cc: <stable@vger.kernel.org> >> --- >> sound/usb/mixer_quirks.c | 37 +++++++++++++++++++++++++++++++++++++ >> 1 file changed, 37 insertions(+) >> >> diff --git a/sound/usb/mixer_quirks.c b/sound/usb/mixer_quirks.c >> index 337c317ead6f..39d7f34e44e6 100644 >> --- a/sound/usb/mixer_quirks.c >> +++ b/sound/usb/mixer_quirks.c >> @@ -37,6 +37,7 @@ >> #include <sound/control.h> >> #include <sound/hwdep.h> >> #include <sound/info.h> >> +#include <sound/tlv.h> >> >> #include "usbaudio.h" >> #include "mixer.h" >> @@ -1733,6 +1734,38 @@ static int snd_microii_controls_create(struct >> usb_mixer_interface *mixer) >> return 0; >> } >> >> +static void snd_dragonfly_quirk_db_scale(struct usb_mixer_interface *mixer) >> +{ >> + struct usb_mixer_elem_list *list; >> + struct usb_mixer_elem_info *cval; >> + static const int unit_id = 7; >> + >> + /* approximation using 10 ranges based on output measurement on hw v1.2 >> */ >> + static const DECLARE_TLV_DB_RANGE(scale, >> + 0, 1, TLV_DB_MINMAX_ITEM(-5300, -4970), >> + 2, 5, TLV_DB_MINMAX_ITEM(-4710, -4160), >> + 6, 7, TLV_DB_MINMAX_ITEM(-3884, -3710), >> + 8, 14, TLV_DB_MINMAX_ITEM(-3443, -2560), >> + 15, 16, TLV_DB_MINMAX_ITEM(-2475, -2324), >> + 17, 19, TLV_DB_MINMAX_ITEM(-2228, -2031), >> + 20, 26, TLV_DB_MINMAX_ITEM(-1910, -1393), >> + 27, 31, TLV_DB_MINMAX_ITEM(-1322, -1032), >> + 32, 40, TLV_DB_MINMAX_ITEM(-968, -490), >> + 41, 50, TLV_DB_MINMAX_ITEM(-441, 0), >> + ); >> + >> + for (list = mixer->id_elems[unit_id]; list; list = list->next_id_elem) { >> + cval = (struct usb_mixer_elem_info *)list; >> + if (cval->control == UAC_FU_VOLUME && >> + cval->min == 0 && cval->max == 50) { >> + usb_audio_info(mixer->chip, "applying DragonFly dB >> scale quirk\n"); >> + list->kctl->tlv.p = scale; >> + list->kctl->vd[0].access |= >> SNDRV_CTL_ELEM_ACCESS_TLV_READ; >> + list->kctl->vd[0].access &= >> ~SNDRV_CTL_ELEM_ACCESS_TLV_CALLBACK; >> + } >> + } > > Instead of looking through the list, just hooking at > build_feature_ctl() would be simpler in the end, I think. > E.g. something like: > > --- a/sound/usb/mixer.c > +++ b/sound/usb/mixer.c > @@ -1334,6 +1334,7 @@ static void build_feature_ctl(struct mixer_build > *state, void *raw_desc, > SNDRV_CTL_ELEM_ACCESS_TLV_READ | > SNDRV_CTL_ELEM_ACCESS_TLV_CALLBACK; > } > + mixer_fu_apply_quirk(state->mixer, cval, unitid, kctl); > } > > range = (cval->max - cval->min) / cval->res; > > ... and the quirk implementation in mixer_quirks.c like > > static void snd_dragonfly_quirk_db_scale(mixer, kctl) > { > usb_audio_info(mixer->chip, "applying DragonFly dB scale quirk\n"); > kctl->tlv.p = scale; > kctl->vd[0].access |= SNDRV_CTL_ELEM_ACCESS_TLV_READ; > list->kctl->vd[0].access &= ~SNDRV_CTL_ELEM_ACCESS_TLV_CALLBACK; > } > > void mixer_fu_apply_quirk(mixer, cval, unitid, kctl) > { > switch (mixer->chip->usb_id) { > case USB_ID(0x21b4, 0x0081): /* AudioQuest DragonFly */ > if (unitid == 7 && cval->min == 0 && cval->max == 50) > snd_dragonfly_quirk_db_scale(mixer, kctl); > break; > } > }
OK, seems like a good idea. However, I just noticed another volume quirk for DragonFly has already been merged since I started looking into this: https://git.kernel.org/cgit/linux/kernel/git/tiwai/sound.git/commit/?id=2d1cb7f658fb9c3ba8f9dab8aca297d4dfdec835 It sets a fixed dB linear range map of 0...50dB via mixer_maps.c, which doesn't seem 100% right to me. While it is much better than the unquirked 0...0.2dB, it causes e.g. pulseaudio mixer to show the nearly inaudible raw 0 as the "base" level. And, unless I made some silly mistake, the volume scale is not actually linear dB AFAICS. Yao-Wen, did you have some basis for the assumption "dB conversion factor is 1" on DragonFly other than that it sounded approximately right? Takashi, should I add removal of that "duplicate" quirk in the same commit (or a separate one)? (assuming my quirk turns out to be actually better/correct, of course) -- Anssi Hannula -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html