From 67a1dba11405ca6dd63f31364d564899983b3ae4 Mon Sep 17 00:00:00 2001 From: Takashi Iwai Date: Tue, 23 Mar 2021 12:01:00 +0000 Subject: [PATCH] ALSA: usb-audio: Drop bogus dB range in too low level MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit stable inclusion from stable-5.10.22 commit 86c524934277b279785659f7b453b31c8d143d0e bugzilla: 50796 -------------------------------- commit 21cba9c5359dd9d1bffe355336cfec0b66d1ee52 upstream. Some USB audio firmware seem to report broken dB values for the volume controls, and this screws up applications like PulseAudio who blindly trusts the given data. For example, Edifier G2000 reports a PCM volume from -128dB to -127dB, and this results in barely inaudible sound. This patch adds a sort of sanity check at parsing the dB values in USB-audio driver and disables the dB reporting if the range looks bogus. Here, we assume -96dB as the bottom line of the max dB. Note that, if one can figure out that proper dB range later, it can be patched in the mixer maps. BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=211929 Cc: Link: https://lore.kernel.org/r/20210227105737.3656-1-tiwai@suse.de Signed-off-by: Takashi Iwai Signed-off-by: Greg Kroah-Hartman Signed-off-by: Chen Jun Acked-by:  Weilong Chen Signed-off-by: Zheng Zengkai --- sound/usb/mixer.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c index 81e987eaf063..375cfb9c9ab7 100644 --- a/sound/usb/mixer.c +++ b/sound/usb/mixer.c @@ -1301,6 +1301,17 @@ static int get_min_max_with_quirks(struct usb_mixer_elem_info *cval, /* totally crap, return an error */ return -EINVAL; } + } else { + /* if the max volume is too low, it's likely a bogus range; + * here we use -96dB as the threshold + */ + if (cval->dBmax <= -9600) { + usb_audio_info(cval->head.mixer->chip, + "%d:%d: bogus dB values (%d/%d), disabling dB reporting\n", + cval->head.id, mixer_ctrl_intf(cval->head.mixer), + cval->dBmin, cval->dBmax); + cval->dBmin = cval->dBmax = 0; + } } return 0; -- GitLab