From mboxrd@z Thu Jan 1 00:00:00 1970 From: Takashi Iwai Subject: Re: [PATCH] ALSA: usb-audio: Fix the mixer control range limiting issue Date: Wed, 21 Aug 2019 19:05:01 +0200 Message-ID: References: <20190821100225.9254-1-srinivas.kandagatla@linaro.org> Mime-Version: 1.0 (generated by SEMI 1.14.6 - "Maruoka") Content-Type: text/plain; charset=US-ASCII Return-path: In-Reply-To: <20190821100225.9254-1-srinivas.kandagatla@linaro.org> Sender: linux-kernel-owner@vger.kernel.org To: Srinivas Kandagatla Cc: broonie@kernel.org, alsa-devel@alsa-project.org, linux-kernel@vger.kernel.org, lgirdwood@gmail.com, Deepa Madiregama , Banajit Goswami , Meng Wang List-Id: alsa-devel@alsa-project.org On Wed, 21 Aug 2019 12:02:25 +0200, Srinivas Kandagatla wrote: > > From: Deepa Madiregama > > - mixer_ctl_set() function is limiting the volume level > to particular range. This results in incorrect initial > volume setting for that device. > - In USB mixer while calculating the dBmin/dBmax values > resolution factor is hardcoded to 256 which results in > populating the wrong values for dBmin/dBmax. > - Fix is to use appropriate resolution factor while > calculating the dBmin/dBmax values. This change doesn't sound right. Basically the values returned from USB-audio FEATURE UNIT or MIXER UNIT are always in 1/256 dB unit, per definition. And we pass dB min/max to user-space as TLV_DB_MINMAX(), i.e. TLV points just both min and max, no matter what scale is. I believe that the current code is correct in this regard. So, it's either a firmware bug that gives the wrong values back, or the case we still don't cover, e.g. multiple RANGE values for UAC2/UAC3. Please check what exactly doesn't work as expected. Which value is returned from the USB-audio device and what is wrongly interpreted. thanks, Takashi > Signed-off-by: Deepa Madiregama > Signed-off-by: Banajit Goswami > Signed-off-by: Meng Wang > Signed-off-by: Srinivas Kandagatla > --- > sound/usb/mixer.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c > index 5070a6a76ab3..a67448327d07 100644 > --- a/sound/usb/mixer.c > +++ b/sound/usb/mixer.c > @@ -1248,8 +1248,10 @@ static int get_min_max_with_quirks(struct usb_mixer_elem_info *cval, > /* USB descriptions contain the dB scale in 1/256 dB unit > * while ALSA TLV contains in 1/100 dB unit > */ > - cval->dBmin = (convert_signed_value(cval, cval->min) * 100) / 256; > - cval->dBmax = (convert_signed_value(cval, cval->max) * 100) / 256; > + cval->dBmin = > + (convert_signed_value(cval, cval->min) * 100) / (cval->res); > + cval->dBmax = > + (convert_signed_value(cval, cval->max) * 100) / (cval->res); > if (cval->dBmin > cval->dBmax) { > /* something is wrong; assume it's either from/to 0dB */ > if (cval->dBmin < 0) > -- > 2.21.0 >