Re: [PATCH 2/2] ALSA: usb-audio: Add quirk for Plantronics headsets to fix control names

[Takashi Iwai <tiwai@xxxxxxx>]

On Sun, 24 Nov 2024 21:32:41 +0100,
Terry Junge wrote:
> 
> Many Poly/Plantronics headset families name the feature, input,
> and/or output units in a such a way to produce control names
> that are not recognized by user space. As such, the volume and
> mute events do not get routed to the headset's audio controls.
> 
> As an example from a product family:
> 
> The microphone mute control is named
> Headset Microphone Capture Switch
> and the headset volume control is named
> Headset Earphone Playback Volume
> 
> The quirk fixes these to become
> Headset Capture Switch
> Headset Playback Volume
> 
> Signed-off-by: Terry Junge <linuxhid@xxxxxxxxxxxxxxxxxxxxxx>

Thanks, this description looks much more understandable now.
Meanwhile...

> ---
>  sound/usb/mixer_quirks.c | 35 +++++++++++++++++++++++++++++++++++
>  1 file changed, 35 insertions(+)
> 
> diff --git a/sound/usb/mixer_quirks.c b/sound/usb/mixer_quirks.c
> index 8bbf070b3676..20d63efd5498 100644
> --- a/sound/usb/mixer_quirks.c
> +++ b/sound/usb/mixer_quirks.c
> @@ -4215,6 +4215,37 @@ static void snd_dragonfly_quirk_db_scale(struct usb_mixer_interface *mixer,
>  	}
>  }
>  
> +static void snd_fix_plt_control_name(struct snd_kcontrol *kctl)
> +{
> +	static const char * const names_to_remove[] = {
> +		"Earphone",
> +		"Microphone",
> +		"Receive",
> +		"Transmit",
> +		NULL
> +	};
> +	const char * const *n2r;
> +	char *dst, *src;
> +	size_t len;
> +
> +	for (n2r = names_to_remove; *n2r; ++n2r) {
> +		dst = strstr(kctl->id.name, *n2r);
> +		if (dst) {
> +			src = dst + strlen(*n2r);
> +			len = strlen(src) + 1;
> +			if ((char *)kctl->id.name != dst && *(dst - 1) == ' ')
> +				--dst;
> +			memmove(dst, src, len);
> +		}
> +	}
> +	if (kctl->id.name[0] == ' ') {
> +		char rcat[sizeof(kctl->id.name)] = { "Headset" };
> +
> +		strlcat(rcat, kctl->id.name, sizeof(rcat));
> +		strscpy(kctl->id.name, rcat, sizeof(kctl->id.name));
> +	}
> +}

... the code itself isn't really trivial (due to the poor string
handling by nature of C language), so it's better to put some brief
comment what this function really does, too.


thanks,

Takashi