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.htmlSigned-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.comSigned-off-by: Takashi Iwai <tiwai@suse.de>

include/uapi/linux/virtio_snd.h

@@ -7,6 +7,14 @@
 
 #include <linux/virtio_types.h>
 
+/*******************************************************************************
+ * FEATURE BITS
+ */
+enum {
+	/* device supports control elements */
+	VIRTIO_SND_F_CTLS = 0
+};
+
 /*******************************************************************************
  * CONFIGURATION SPACE
  */
@@ -17,6 +25,8 @@ struct virtio_snd_config {
 	__le32 streams;
 	/* # of available channel maps */
 	__le32 chmaps;
+	/* # of available control elements */
+	__le32 controls;
 };
 
 enum {
@@ -55,6 +65,15 @@ enum {
 	/* channel map control request types */
 	VIRTIO_SND_R_CHMAP_INFO = 0x0200,
 
+	/* 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,
+
 	/* jack event types */
 	VIRTIO_SND_EVT_JACK_CONNECTED = 0x1000,
 	VIRTIO_SND_EVT_JACK_DISCONNECTED,
@@ -63,6 +82,9 @@ enum {
 	VIRTIO_SND_EVT_PCM_PERIOD_ELAPSED = 0x1100,
 	VIRTIO_SND_EVT_PCM_XRUN,
 
+	/* control element event types */
+	VIRTIO_SND_EVT_CTL_NOTIFY = 0x1200,
+
 	/* common status codes */
 	VIRTIO_SND_S_OK = 0x8000,
 	VIRTIO_SND_S_BAD_MSG,
@@ -331,4 +353,136 @@ struct virtio_snd_chmap_info {
 	__u8 positions[VIRTIO_SND_CHMAP_MAX_SIZE];
 };
 
+/*******************************************************************************
+ * CONTROL ELEMENTS MESSAGES
+ */
+struct virtio_snd_ctl_hdr {
+	/* VIRTIO_SND_R_CTL_XXX */
+	struct virtio_snd_hdr hdr;
+	/* 0 ... virtio_snd_config::controls - 1 */
+	__le32 control_id;
+};
+
+/* supported roles for control elements */
+enum {
+	VIRTIO_SND_CTL_ROLE_UNDEFINED = 0,
+	VIRTIO_SND_CTL_ROLE_VOLUME,
+	VIRTIO_SND_CTL_ROLE_MUTE,
+	VIRTIO_SND_CTL_ROLE_GAIN
+};
+
+/* supported value types for control elements */
+enum {
+	VIRTIO_SND_CTL_TYPE_BOOLEAN = 0,
+	VIRTIO_SND_CTL_TYPE_INTEGER,
+	VIRTIO_SND_CTL_TYPE_INTEGER64,
+	VIRTIO_SND_CTL_TYPE_ENUMERATED,
+	VIRTIO_SND_CTL_TYPE_BYTES,
+	VIRTIO_SND_CTL_TYPE_IEC958
+};
+
+/* supported access rights for control elements */
+enum {
+	VIRTIO_SND_CTL_ACCESS_READ = 0,
+	VIRTIO_SND_CTL_ACCESS_WRITE,
+	VIRTIO_SND_CTL_ACCESS_VOLATILE,
+	VIRTIO_SND_CTL_ACCESS_INACTIVE,
+	VIRTIO_SND_CTL_ACCESS_TLV_READ,
+	VIRTIO_SND_CTL_ACCESS_TLV_WRITE,
+	VIRTIO_SND_CTL_ACCESS_TLV_COMMAND
+};
+
+struct virtio_snd_ctl_info {
+	/* common header */
+	struct virtio_snd_info hdr;
+	/* element role (VIRTIO_SND_CTL_ROLE_XXX) */
+	__le32 role;
+	/* element value type (VIRTIO_SND_CTL_TYPE_XXX) */
+	__le32 type;
+	/* element access right bit map (1 << VIRTIO_SND_CTL_ACCESS_XXX) */
+	__le32 access;
+	/* # of members in the element value */
+	__le32 count;
+	/* index for an element with a non-unique name */
+	__le32 index;
+	/* name identifier string for the element */
+	__u8 name[44];
+	/* additional information about the element's value */
+	union {
+		/* VIRTIO_SND_CTL_TYPE_INTEGER */
+		struct {
+			/* minimum supported value */
+			__le32 min;
+			/* maximum supported value */
+			__le32 max;
+			/* fixed step size for value (0 = variable size) */
+			__le32 step;
+		} integer;
+		/* VIRTIO_SND_CTL_TYPE_INTEGER64 */
+		struct {
+			/* minimum supported value */
+			__le64 min;
+			/* maximum supported value */
+			__le64 max;
+			/* fixed step size for value (0 = variable size) */
+			__le64 step;
+		} integer64;
+		/* VIRTIO_SND_CTL_TYPE_ENUMERATED */
+		struct {
+			/* # of options supported for value */
+			__le32 items;
+		} enumerated;
+	} value;
+};
+
+struct virtio_snd_ctl_enum_item {
+	/* option name */
+	__u8 item[64];
+};
+
+struct virtio_snd_ctl_iec958 {
+	/* AES/IEC958 channel status bits */
+	__u8 status[24];
+	/* AES/IEC958 subcode bits */
+	__u8 subcode[147];
+	/* nothing */
+	__u8 pad;
+	/* AES/IEC958 subframe bits */
+	__u8 dig_subframe[4];
+};
+
+struct virtio_snd_ctl_value {
+	union {
+		/* VIRTIO_SND_CTL_TYPE_BOOLEAN|INTEGER value */
+		__le32 integer[128];
+		/* VIRTIO_SND_CTL_TYPE_INTEGER64 value */
+		__le64 integer64[64];
+		/* VIRTIO_SND_CTL_TYPE_ENUMERATED value (option indexes) */
+		__le32 enumerated[128];
+		/* VIRTIO_SND_CTL_TYPE_BYTES value */
+		__u8 bytes[512];
+		/* VIRTIO_SND_CTL_TYPE_IEC958 value */
+		struct virtio_snd_ctl_iec958 iec958;
+	} value;
+};
+
+/* supported event reason types */
+enum {
+	/* element's value has changed */
+	VIRTIO_SND_CTL_EVT_MASK_VALUE = 0,
+	/* element's information has changed */
+	VIRTIO_SND_CTL_EVT_MASK_INFO,
+	/* element's metadata has changed */
+	VIRTIO_SND_CTL_EVT_MASK_TLV
+};
+
+struct virtio_snd_ctl_event {
+	/* VIRTIO_SND_EVT_CTL_NOTIFY */
+	struct virtio_snd_hdr hdr;
+	/* 0 ... virtio_snd_config::controls - 1 */
+	__le16 control_id;
+	/* event reason bit map (1 << VIRTIO_SND_CTL_EVT_MASK_XXX) */
+	__le16 mask;
+};
+
 #endif /* VIRTIO_SND_IF_H */

sound/virtio/Makefile

@@ -7,6 +7,7 @@ virtio_snd-objs := \
 	virtio_chmap.o \
 	virtio_ctl_msg.o \
 	virtio_jack.o \
+	virtio_kctl.o \
 	virtio_pcm.o \
 	virtio_pcm_msg.o \
 	virtio_pcm_ops.o

sound/virtio/virtio_card.c

@@ -64,6 +64,9 @@ static void virtsnd_event_dispatch(struct virtio_snd *snd,
 	case VIRTIO_SND_EVT_PCM_XRUN:
 		virtsnd_pcm_event(snd, event);
 		break;
+	case VIRTIO_SND_EVT_CTL_NOTIFY:
+		virtsnd_kctl_event(snd, event);
+		break;
 	}
 }
 
@@ -233,6 +236,12 @@ static int virtsnd_build_devs(struct virtio_snd *snd)
 	if (rc)
 		return rc;
 
+	if (virtio_has_feature(vdev, VIRTIO_SND_F_CTLS)) {
+		rc = virtsnd_kctl_parse_cfg(snd);
+		if (rc)
+			return rc;
+	}
+
 	if (snd->njacks) {
 		rc = virtsnd_jack_build_devs(snd);
 		if (rc)
@@ -251,6 +260,12 @@ static int virtsnd_build_devs(struct virtio_snd *snd)
 			return rc;
 	}
 
+	if (snd->nkctls) {
+		rc = virtsnd_kctl_build_devs(snd);
+		if (rc)
+			return rc;
+	}
+
 	return snd_card_register(snd->card);
 }
 
@@ -417,10 +432,16 @@ static const struct virtio_device_id id_table[] = {
 	{ 0 },
 };
 
+static unsigned int features[] = {
+	VIRTIO_SND_F_CTLS
+};
+
 static struct virtio_driver virtsnd_driver = {
 	.driver.name = KBUILD_MODNAME,
 	.driver.owner = THIS_MODULE,
 	.id_table = id_table,
+	.feature_table = features,
+	.feature_table_size = ARRAY_SIZE(features),
 	.validate = virtsnd_validate,
 	.probe = virtsnd_probe,
 	.remove = virtsnd_remove,

sound/virtio/virtio_card.h

@@ -31,6 +31,16 @@ struct virtio_snd_queue {
 	struct virtqueue *vqueue;
 };
 
+/**
+ * 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.
@@ -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 */