Re: [PATCH v28 30/32] ALSA: usb-audio: Add USB offload route kcontrol

+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;

+}