Re: [PATCH 1/2 v2] ALSA: usb-audio: Add a more accurate volume quirk for AudioQuest DragonFly

[Takashi Iwai <tiwai@suse.de>]

On Sun, 13 Dec 2015 19:49:58 +0100,
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 would cause software using the dB information
> in e.g. volume sliders to have a massive volume difference in 100..102%
> range.
> 
> Commit 2d1cb7f658fb ("ALSA: usb-audio: add dB range mapping for some
> devices") added a dB range mapping for it with range 0..50 dB.
> 
> However, 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 approx. -53...0 dB.
> 
> Replace the previous quirk with a custom dB mapping based on some basic
> output measurements, using a 10-item range TLV (which will still fit 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.
> 
> v2: incorporated Takashi Iwai's suggestion for the quirk application
> method
> 
> Signed-off-by: Anssi Hannula <anssi.hannula@iki.fi>
> Cc: <stable@vger.kernel.org>

Applied, thanks.


Takashi

> ---
> 
> It took a bit longer than expected for me to get back to this, but here
> goes :)
> 
> 
>  sound/usb/mixer.c        |  2 ++
>  sound/usb/mixer_maps.c   | 12 ------------
>  sound/usb/mixer_quirks.c | 37 +++++++++++++++++++++++++++++++++++++
>  sound/usb/mixer_quirks.h |  4 ++++
>  4 files changed, 43 insertions(+), 12 deletions(-)
> 
> diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c
> index f494dced3c11..4f85757009b3 100644
> --- a/sound/usb/mixer.c
> +++ b/sound/usb/mixer.c
> @@ -1354,6 +1354,8 @@ static void build_feature_ctl(struct mixer_build *state, void *raw_desc,
>  		}
>  	}
>  
> +	snd_usb_mixer_fu_apply_quirk(state->mixer, cval, unitid, kctl);
> +
>  	range = (cval->max - cval->min) / cval->res;
>  	/*
>  	 * Are there devices with volume range more than 255? I use a bit more
> diff --git a/sound/usb/mixer_maps.c b/sound/usb/mixer_maps.c
> index 6a803eff87f7..ddca6547399b 100644
> --- a/sound/usb/mixer_maps.c
> +++ b/sound/usb/mixer_maps.c
> @@ -348,13 +348,6 @@ static struct usbmix_name_map bose_companion5_map[] = {
>  	{ 0 }	/* terminator */
>  };
>  
> -/* Dragonfly DAC 1.2, the dB conversion factor is 1 instead of 256 */
> -static struct usbmix_dB_map dragonfly_1_2_dB = {0, 5000};
> -static struct usbmix_name_map dragonfly_1_2_map[] = {
> -	{ 7, NULL, .dB = &dragonfly_1_2_dB },
> -	{ 0 }	/* terminator */
> -};
> -
>  /*
>   * Control map entries
>   */
> @@ -470,11 +463,6 @@ static struct usbmix_ctl_map usbmix_ctl_maps[] = {
>  		.id = USB_ID(0x05a7, 0x1020),
>  		.map = bose_companion5_map,
>  	},
> -	{
> -		/* Dragonfly DAC 1.2 */
> -		.id = USB_ID(0x21b4, 0x0081),
> -		.map = dragonfly_1_2_map,
> -	},
>  	{ 0 } /* terminator */
>  };
>  
> diff --git a/sound/usb/mixer_quirks.c b/sound/usb/mixer_quirks.c
> index fe91184ce832..0ce888dceed0 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"
> @@ -1825,3 +1826,39 @@ void snd_usb_mixer_rc_memory_change(struct usb_mixer_interface *mixer,
>  	}
>  }
>  
> +static void snd_dragonfly_quirk_db_scale(struct usb_mixer_interface *mixer,
> +					 struct snd_kcontrol *kctl)
> +{
> +	/* Approximation using 10 ranges based on output measurement on hw v1.2.
> +	 * This seems close to the cubic mapping e.g. alsamixer uses. */
> +	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),
> +	);
> +
> +	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;
> +	kctl->vd[0].access &= ~SNDRV_CTL_ELEM_ACCESS_TLV_CALLBACK;
> +}
> +
> +void snd_usb_mixer_fu_apply_quirk(struct usb_mixer_interface *mixer,
> +				  struct usb_mixer_elem_info *cval, int unitid,
> +				  struct snd_kcontrol *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;
> +	}
> +}
> +
> diff --git a/sound/usb/mixer_quirks.h b/sound/usb/mixer_quirks.h
> index bdbfab093816..177c329cd4dd 100644
> --- a/sound/usb/mixer_quirks.h
> +++ b/sound/usb/mixer_quirks.h
> @@ -9,5 +9,9 @@ void snd_emuusb_set_samplerate(struct snd_usb_audio *chip,
>  void snd_usb_mixer_rc_memory_change(struct usb_mixer_interface *mixer,
>  				    int unitid);
>  
> +void snd_usb_mixer_fu_apply_quirk(struct usb_mixer_interface *mixer,
> +				  struct usb_mixer_elem_info *cval, int unitid,
> +				  struct snd_kcontrol *kctl);
> +
>  #endif /* SND_USB_MIXER_QUIRKS_H */
>  
> -- 
> 2.3.10
>