ALSA: virtio: add support for audio controls

Implementation of support for audio controls in accordance with the
extension of the virtio sound device specification [1] planned for
virtio-v1.3-cs01.

The device can announce the VIRTIO_SND_F_CTLS feature. If the feature is
negotiated, then an additional field appears in the configuration space:

  struct virtio_snd_config {
    ...
    /* number of available control elements */
    __le32 controls;
  };

The driver can send the following requests to manage audio controls:

  enum {
    ...
    /* control element request types */
    VIRTIO_SND_R_CTL_INFO = 0x0300,
    VIRTIO_SND_R_CTL_ENUM_ITEMS,
    VIRTIO_SND_R_CTL_READ,
    VIRTIO_SND_R_CTL_WRITE,
    VIRTIO_SND_R_CTL_TLV_READ,
    VIRTIO_SND_R_CTL_TLV_WRITE,
    VIRTIO_SND_R_CTL_TLV_COMMAND,
    ...
  };

And the device can send the following audio control event notification:

  enum {
    ...
    /* control element event types */
    VIRTIO_SND_EVT_CTL_NOTIFY = 0x1200,
    ...
  };

See additional details in [1].

[1] https://lists.oasis-open.org/archives/virtio-comment/202104/msg00013.html

Signed-off-by: Anton Yakovlev <anton.yakovlev@opensynergy.com>
Signed-off-by: Aiswarya Cyriac <aiswarya.cyriac@opensynergy.com>
Link: https://lore.kernel.org/r/20240115133654.576068-2-aiswarya.cyriac@opensynergy.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>

1 files changed, 22 insertions, 0 deletions

diff --git a/sound/virtio/virtio_card.h b/sound/virtio/virtio_card.h
index 86ef3941895e..3ceee4e416fc 100644
--- a/sound/virtio/virtio_card.h
+++ b/sound/virtio/virtio_card.h
@@ -32,6 +32,16 @@ struct virtio_snd_queue {
 };
 
 /**
+ * struct virtio_kctl - VirtIO control element.
+ * @kctl: ALSA control element.
+ * @items: Items for the ENUMERATED element type.
+ */
+struct virtio_kctl {
+	struct snd_kcontrol *kctl;
+	struct virtio_snd_ctl_enum_item *items;
+};
+
+/**
  * struct virtio_snd - VirtIO sound card device.
  * @vdev: Underlying virtio device.
  * @queues: Virtqueue wrappers.
@@ -45,6 +55,9 @@ struct virtio_snd_queue {
  * @nsubstreams: Number of PCM substreams.
  * @chmaps: VirtIO channel maps.
  * @nchmaps: Number of channel maps.
+ * @kctl_infos: VirtIO control element information.
+ * @kctls: VirtIO control elements.
+ * @nkctls: Number of control elements.
  */
 struct virtio_snd {
 	struct virtio_device *vdev;
@@ -59,6 +72,9 @@ struct virtio_snd {
 	u32 nsubstreams;
 	struct virtio_snd_chmap_info *chmaps;
 	u32 nchmaps;
+	struct virtio_snd_ctl_info *kctl_infos;
+	struct virtio_kctl *kctls;
+	u32 nkctls;
 };
 
 /* Message completion timeout in milliseconds (module parameter). */
@@ -108,4 +124,10 @@ int virtsnd_chmap_parse_cfg(struct virtio_snd *snd);
 
 int virtsnd_chmap_build_devs(struct virtio_snd *snd);
 
+int virtsnd_kctl_parse_cfg(struct virtio_snd *snd);
+
+int virtsnd_kctl_build_devs(struct virtio_snd *snd);
+
+void virtsnd_kctl_event(struct virtio_snd *snd, struct virtio_snd_event *event);
+
 #endif /* VIRTIO_SND_CARD_H */