Re: [PATCH 2/2] ALSA: usb-audio: Add ES9219 speaker volume for ASRock X870E Taichi

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 2 potential
issues to consider:
- [Medium] ALSA: usb-audio: premature private_value update in
  taichi_es9219_vol_put()
- [Low] ALSA: usb-audio: wrong feature unit ID in taichi_es9219 comment
--

commit 67dc6589a98098f31e87c384d4ca4f8074ecf8d0
Author: Brian Harring <ferringb@gmail.com>

ALSA: usb-audio: Add ES9219 speaker volume for ASRock X870E Taichi

This commit adds a Speaker Playback Volume mixer control for the ASRock
X870E Taichi and Taichi Lite onboard audio by accessing the ESS ES9219
DAC over the ALC4082 codec's I2C bridge.

> diff --git a/sound/usb/mixer_quirks.c b/sound/usb/mixer_quirks.c
> index 4c7d68311f204..075fb5847030f 100644
> --- a/sound/usb/mixer_quirks.c
> +++ b/sound/usb/mixer_quirks.c
> @@ -4656,6 +4656,159 @@ static int snd_xiisound_init_fu_pins(struct usb_mixer_interface *mixer)
>  	return 0;
>  }
>  
> +/*
> + * ASRock X870E Taichi (ALC4082): the rear line exposes only mute (feature
> + * unit 19), but there is an ESS ES9219 DAC behind it that is usable for
> + * volume control.
> + */

[Severity: Low]
This isn't a bug, but should this comment say feature unit 29 rather than
19?  In sound/usb/mixer_maps.c, alc408x_map maps unit 29 to "Speaker
Playback" for USB_ID(0x26ce, 0x0a0b).

[ ... ]

> +static int taichi_es9219_vol_put(struct snd_kcontrol *kctl,
> +				 struct snd_ctl_elem_value *ucontrol)
> +{
> +	struct usb_mixer_elem_list *list = snd_kcontrol_chip(kctl);
> +	long l = ucontrol->value.integer.value[0];
> +	long r = ucontrol->value.integer.value[1];
> +	unsigned long pv;
> +	int err;
> +
> +	if (l < 0 || l > TAICHI_ES9219_VOL_MAX ||
> +	    r < 0 || r > TAICHI_ES9219_VOL_MAX)
> +		return -EINVAL;
> +
> +	pv = l | (r << 8);
> +	if (pv == kctl->private_value)
> +		return 0;
> +
> +	kctl->private_value = pv;
> +	err = taichi_es9219_vol_update(list->mixer, pv);
> +	return err < 0 ? err : 1;
> +}

[Severity: Medium]
Should kctl->private_value be updated only after taichi_es9219_vol_update()
succeeds?

If taichi_es9219_vol_update() fails, kctl->private_value retains the
unwritten volume.  taichi_es9219_vol_get() then reports the wrong value to
userspace, and retrying the same volume in taichi_es9219_vol_put() hits the
pv == kctl->private_value check and returns 0 without writing to the DAC.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261108-alc4082-taichi-v1-0-942558088157@gmail.com?part=2