> +static int
> +snd_usb_offload_route_get(struct snd_kcontrol *kcontrol,
> + struct snd_ctl_elem_value *ucontrol)
> +{
> + struct device *sysdev = snd_kcontrol_chip(kcontrol);
> + int ret;
> +
> + ret = snd_soc_usb_update_offload_route(sysdev,
> + CARD_IDX(kcontrol->private_value),
> + PCM_IDX(kcontrol->private_value),
> + SNDRV_PCM_STREAM_PLAYBACK,
> + ucontrol->value.integer.value);
> + if (ret < 0) {
> + ucontrol->value.integer.value[0] = -1;
> + ucontrol->value.integer.value[1] = -1;
> + }
well this invalidates again what I understood from the last patch and
goes back to what I understood initially: the error code is never
returned to higher levels - when offload is not supported the kcontrol
values are encoded to the -1 magic value.
> + return 0;
and this begs the question if this helper should return a void value.
> +}
> +
> +static int snd_usb_offload_route_info(struct snd_kcontrol *kcontrol,
> + struct snd_ctl_elem_info *uinfo)
> +{
> + uinfo->type = SNDRV_CTL_ELEM_TYPE_INTEGER;
> + uinfo->count = 2;
> + uinfo->value.integer.min = -1;
> + /* Arbitrary max value, as there is no 'limit' on number of PCM devices */
> + uinfo->value.integer.max = 0xff;
> +
> + return 0;
> +}
> +
> +static struct snd_kcontrol_new snd_usb_offload_mapped_ctl = {
> + .iface = SNDRV_CTL_ELEM_IFACE_CARD,
> + .access = SNDRV_CTL_ELEM_ACCESS_READ,
> + .info = snd_usb_offload_route_info,
> + .get = snd_usb_offload_route_get,
> +};
> +
> +/**
> + * snd_usb_offload_create_ctl() - Add USB offload bounded mixer
> + * @chip - USB SND chip device
> + *
> + * Creates a sound control for a USB audio device, so that applications can
> + * query for if there is an available USB audio offload path, and which
> + * card is managing it.
> + */
> +int snd_usb_offload_create_ctl(struct snd_usb_audio *chip)
> +{
> + struct usb_device *udev = chip->dev;
> + struct snd_kcontrol_new *chip_kctl;
> + struct snd_usb_substream *subs;
> + struct snd_usb_stream *as;
> + char ctl_name[37];
that's quite a magic value.
> + int ret;
> +
> + list_for_each_entry(as, &chip->pcm_list, list) {
> + subs = &as->substream[SNDRV_PCM_STREAM_PLAYBACK];
> + if (!subs->ep_num)
> + continue;
> +
> + chip_kctl = &snd_usb_offload_mapped_ctl;
> + chip_kctl->count = 1;
> + /*
> + * Store the associated USB SND card number and PCM index for
> + * the kctl.
> + */
> + chip_kctl->private_value = as->pcm_index |
> + chip->card->number << 16;
> + sprintf(ctl_name, "USB Offload Playback Route PCM#%d",
> + as->pcm_index);
> + chip_kctl->name = ctl_name;
> + ret = snd_ctl_add(chip->card, snd_ctl_new1(chip_kctl,
> + udev->bus->sysdev));
> + if (ret < 0)
> + break;
> + }
> +
> + return ret;
> +}
