Takashi Iwai <tiwai@xxxxxxx> 於 2021年9月9日 週四 下午9:30寫道：
>
> On Thu, 09 Sep 2021 12:21:46 +0200,
> En-Shuo Hsu wrote:
> >
> > Hi
> >
> > We recently found that some USB headsets may fall back to their full volume
> > after a suspend and resume. We think the issue is caused by the logic of
> > mixer_ctl_feature_put in sound/usb/mixer.c:
> >
> > err = snd_usb_get_cur_mix_value(cval, c + 1, cnt, &oval);
> > if (err < 0)
> > return filter_error(cval, err);
> > val = ucontrol->value.integer.value[cnt];
> > val = get_abs_value(cval, val);
> > if (oval != val) {
> > snd_usb_set_cur_mix_value(cval, c + 1, cnt, val);
> > changed = 1;
> > }
> >
> > The existing codes get the existing mixer control value and ignore the set if
> > the val doesn't change. However, in the suspend and resume case, the USB
> > headset's control value is actually changed.
> >
> > Removing the cache logic is a potential fix, but a better solution may be to
> > properly handle the suspend resume scenario in snd_usb_get_cur_mix_value. We
> > may need to mark the cache in usb_mixer_elem_info to be dirty.
> >
> > The issue is verified to be reproduced with Dell WH3022 and Logitech USB
> > Headset H340 by:
> > 1. Boot to OS.
> > 2. Plug in the headset and check sound output.
> > 3. Play an audio/video and keep with low volume.
> > 4. Suspend.
> > 5. Resume.
> > 6. When audio/video is played, the headset's sound output can't keep the
> > original volume. --> issue "
> >
> > Would like to know your thoughts on this issue.
>
> USB-audio driver has an assumption that the normal resume code
> presumes the configuration while reset_resume needs the full
> initialization, but this looks too naive, then.
>
> Could you check the following works?
>
>
> Takashi
>
> --- a/sound/usb/card.c
> +++ b/sound/usb/card.c
> @@ -1080,7 +1080,7 @@ static int __usb_audio_resume(struct usb_interface *intf, bool reset_resume)
> * we just notify and restart the mixers
> */
> list_for_each_entry(mixer, &chip->mixer_list, list) {
> - err = snd_usb_mixer_resume(mixer, reset_resume);
> + err = snd_usb_mixer_resume(mixer, true /*reset_resume*/);
> if (err < 0)
> goto err_out;
> }
Thanks! It works. Is it an appropriate fix to set the reset_resume to
true in usb_audio_resume?
If it's acceptable, we can send the patch.
Yu-Hsuan
