Re: [alsa-devel] [PATCH 4/4] ALSA: usb: add UAC3 BADD profiles support

[Takashi Iwai]

On Sat, 14 Apr 2018 00:24:26 +0200,
Ruslan Bilovol wrote:
> 
> +static void build_feature_ctl_badd(struct usb_mixer_interface *mixer,
> +			      unsigned int ctl_mask, int control, int unitid,
> +			      const struct usbmix_name_map *badd_map)
> +{
....
> +	kctl = snd_ctl_new1(&usb_feature_unit_ctl, cval);
> +
> +	if (!kctl) {
> +		usb_audio_err(mixer->chip, "cannot malloc kcontrol\n");

No need for error message after malloc failure.  The kernel is already
chatty about it.


> +static int snd_usb_mixer_controls_badd(struct usb_mixer_interface *mixer,
> +				       int ctrlif)
> +{
> +	struct usb_device *dev = mixer->chip->dev;
> +	struct usb_interface_assoc_descriptor *assoc;
> +	int badd_profile = mixer->chip->badd_profile;
> +	const struct usbmix_ctl_map *map;
> +	int p_chmask = 0, c_chmask = 0, st_chmask = 0;
> +	int i;
> +
> +	assoc = usb_ifnum_to_if(dev, ctrlif)->intf_assoc;
> +
> +	/* Detect BADD capture/playback channels from AS EP descriptors */
> +	for (i = 0; i < assoc->bInterfaceCount; i++) {
> +		int intf = assoc->bFirstInterface + i;
> +
> +		if (intf != ctrlif) {

In this case, it's better to skip like

		if (intf == ctrlif)
			continue;

so that we can save an indentation for the whole long block.

> +	switch (badd_profile) {
> +	default:
> +		return -EINVAL;
> +	case UAC3_FUNCTION_SUBCLASS_GENERIC_IO:
> +		/*
> +		 * BAIF, BAOF or combination of both
> +		 * IN: Mono or Stereo cfg, Mono alt possible
> +		 * OUT: Mono or Stereo cfg, Mono alt possible
> +		 */
> +		/* c_chmask := DYNAMIC */
> +		/* p_chmask := DYNAMIC */
> +		if (!c_chmask && !p_chmask) {
> +			usb_audio_err(mixer->chip,
> +				"BADD GENERIC_IO profile: no channels?\n");
> +			return -EINVAL;
> +		}
> +		break;

Maybe we can simplify the whole switch/case with a table lookup.
For example,

	for (f = uac3_func_tables; f->name; f++) {
		if (badd_profile == f->subclass)
			break;
	}
	if (!f->name)
		return -EINVAL;
	if (!uac3_func_has_valid_channels(mixer, f, c_chmask, p_chmask))
		return -EINVAL;
	st_chmask = f->st_chmask;

and in uac3_func_has_valid_channels(),

static bool uac3_func_has_valid_channels()
{
	if ((f->c_chmask < 0 && !c_chmask) ||
	    (f->c_chmask >= 0 && f->c_chmask != c_chmask)) {
		usb_audio_warn(mixer->chip, "BAAD %s c_chmask mismatch",
				f->name);
		return false;
	}
	if ((f->p_chmask < 0 && !p_chmask) ||
	    (f->p_chmask >= 0 && f->p_chmask != p_chmask)) {
		usb_audio_warn(mixer->chip, "BAAD %s p_chmask mismatch",
				f->name);
		return false;
	}
	return true;
}


thanks,

Takashi