shared/vcp: Add initial code for handling VOCS
authorNitin Jadhav <nitin.jadhav@nxp.com>
Mon, 12 Jun 2023 13:32:50 +0000 (19:02 +0530)
committerAyush Garg <ayush.garg@samsung.com>
Fri, 5 Jan 2024 13:34:03 +0000 (19:04 +0530)
Summary:
- This adds implementation for VOCS service and characteristics
- Implementation based on VOCS_v1.0.pdf specification
- Tested using PTS with reference to VOCS.TS.p1.pdf

src/shared/vcp.c

index 8bbb4c0..4667405 100644 (file)
 #define BT_ATT_ERROR_INVALID_CHANGE_COUNTER    0x80
 #define BT_ATT_ERROR_OPCODE_NOT_SUPPORTED      0x81
 
+#define BT_VCP_NA                   BIT(0)
+#define BT_VCP_FRONT_LEFT           BIT(1)
+#define BT_VCP_FRONT_RIGHT          BIT(2)
+#define BT_VCP_FRONT_CENTER         BIT(3)
+#define BT_VCP_LOW_FRQ_EFF_1        BIT(4)
+#define BT_VCP_BACK_LEFT            BIT(5)
+#define BT_VCP_BACK_RIGHT           BIT(6)
+#define BT_VCP_FRONT_LEFT_CENTER    BIT(7)
+#define BT_VCP_FRONT_RIGHT_CENTER   BIT(8)
+#define BT_VCP_BACK_CENTER          BIT(9)
+#define BT_VCP_LOW_FRQ_EFF_2        BIT(10)
+#define BT_VCP_SIDE_LEFT            BIT(11)
+#define BT_VCP_SIDE_RIGHT           BIT(12)
+#define BT_VCP_TOP_FRONT_LEFT       BIT(13)
+#define BT_VCP_TOP_FRONT_RIGHT      BIT(14)
+#define BT_VCP_TOP_FRONT_CENTER     BIT(15)
+#define BT_VCP_TOP_CENTER           BIT(16)
+#define BT_VCP_TOP_BACK_LEFT        BIT(17)
+#define BT_VCP_TOP_BACK_RIGHT       BIT(18)
+#define BT_VCP_TOP_SIDE_LEFT        BIT(19)
+#define BT_VCP_TOP_SIDE_RIGHT       BIT(20)
+#define BT_VCP_TOP_BACK_CENTER      BIT(21)
+#define BT_VCP_BOTTOM_FRONT_CENTER  BIT(22)
+#define BT_VCP_BOTTOM_FRONT_LEFT    BIT(23)
+#define BT_VCP_BOTTOM_FRONT_RIGHT   BIT(24)
+#define BT_VCP_FRONT_LEFT_WIDE      BIT(25)
+#define BT_VCP_FRONT_RIGHT_WIDE     BIT(26)
+#define BT_VCP_LEFT_SURROUND        BIT(27)
+#define BT_VCP_RIGHT_SURROUND       BIT(28)
+
 struct bt_vcp_db {
        struct gatt_db *db;
        struct bt_vcs *vcs;
+       struct bt_vocs *vocs;
 };
 
 typedef void (*vcp_func_t)(struct bt_vcp *vcp, bool success, uint8_t att_ecode,
@@ -57,11 +88,21 @@ struct bt_vcs_param {
        uint8_t change_counter;
 } __packed;
 
+struct bt_vocs_param {
+       uint8_t op;
+       uint8_t change_counter;
+} __packed;
+
 struct bt_vcs_ab_vol {
        uint8_t change_counter;
        uint8_t vol_set;
 } __packed;
 
+struct bt_vocs_set_vol_off {
+       uint8_t change_counter;
+       uint8_t set_vol_offset;
+} __packed;
+
 struct bt_vcp_cb {
        unsigned int id;
        bt_vcp_func_t attached;
@@ -89,6 +130,10 @@ struct bt_vcp {
        unsigned int vstate_id;
        unsigned int vflag_id;
 
+       unsigned int state_id;
+       unsigned int audio_loc_id;
+       unsigned int ao_dec_id;
+
        struct queue *notify;
        struct queue *pending;
 
@@ -120,6 +165,27 @@ struct bt_vcs {
        struct gatt_db_attribute *vf_ccc;
 };
 
+/* Contains local bt_vcp_db */
+struct vol_offset_state {
+       uint16_t vol_offset;
+       uint8_t counter;
+} __packed;
+
+struct bt_vocs {
+       struct bt_vcp_db *vdb;
+       struct vol_offset_state *vostate;
+       uint32_t vocs_audio_loc;
+       char *vocs_ao_dec;
+       struct gatt_db_attribute *service;
+       struct gatt_db_attribute *vos;
+       struct gatt_db_attribute *vos_ccc;
+       struct gatt_db_attribute *voal;
+       struct gatt_db_attribute *voal_ccc;
+       struct gatt_db_attribute *vo_cp;
+       struct gatt_db_attribute *voaodec;
+       struct gatt_db_attribute *voaodec_ccc;
+};
+
 static struct queue *vcp_db;
 static struct queue *vcp_cbs;
 static struct queue *sessions;
@@ -159,6 +225,17 @@ static struct vol_state *vdb_get_vstate(struct bt_vcp_db *vdb)
        return NULL;
 }
 
+static struct vol_offset_state *vdb_get_vostate(struct bt_vcp_db *vdb)
+{
+       if (!vdb->vocs)
+               return NULL;
+
+       if (vdb->vocs->vostate)
+               return vdb->vocs->vostate;
+
+       return NULL;
+}
+
 static struct bt_vcs *vcp_get_vcs(struct bt_vcp *vcp)
 {
        if (!vcp)
@@ -173,6 +250,20 @@ static struct bt_vcs *vcp_get_vcs(struct bt_vcp *vcp)
        return vcp->rdb->vcs;
 }
 
+static struct bt_vocs *vcp_get_vocs(struct bt_vcp *vcp)
+{
+       if (!vcp)
+               return NULL;
+
+       if (vcp->rdb->vocs)
+               return vcp->rdb->vocs;
+
+       vcp->rdb->vocs = new0(struct bt_vocs, 1);
+       vcp->rdb->vocs->vdb = vcp->rdb;
+
+       return vcp->rdb->vocs;
+}
+
 static void vcp_detached(void *data, void *user_data)
 {
        struct bt_vcp_cb *cb = data;
@@ -202,6 +293,7 @@ static void vcp_db_free(void *data)
        gatt_db_unref(vdb->db);
 
        free(vdb->vcs);
+       free(vdb->vocs);
        free(vdb);
 }
 
@@ -583,6 +675,45 @@ static uint8_t vcs_mute(struct bt_vcs *vcs, struct bt_vcp *vcp,
        return 0;
 }
 
+static uint8_t vocs_set_vol_offset(struct bt_vocs *vocs, struct bt_vcp *vcp,
+                               struct iovec *iov)
+{
+       struct bt_vcp_db *vdb;
+       struct vol_offset_state *vstate;
+       struct bt_vocs_set_vol_off *req;
+
+       DBG(vcp, "Set Volume Offset");
+
+       vdb = vcp_get_vdb(vcp);
+       if (!vdb) {
+               DBG(vcp, "error: VDB not available");
+               return 0;
+       }
+
+       vstate = vdb_get_vostate(vdb);
+       if (!vstate) {
+               DBG(vcp, "error: VSTATE not available");
+               return 0;
+       }
+
+       req = iov_pull_mem(iov, sizeof(*req));
+       if (!req)
+               return 0;
+
+       if (req->change_counter != vstate->counter) {
+               DBG(vcp, "Change Counter Mismatch Volume not decremented!");
+               return BT_ATT_ERROR_INVALID_CHANGE_COUNTER;
+       }
+
+       vstate->vol_offset = req->set_vol_offset;
+       vstate->counter = -~vstate->counter; /*Increment Change Counter*/
+
+       gatt_db_attribute_notify(vdb->vocs->vos, (void *)vstate,
+                                sizeof(struct vol_offset_state),
+                                bt_vcp_get_att(vcp));
+       return 0;
+}
+
 #define        BT_VCS_REL_VOL_DOWN             0x00
 #define        BT_VCS_REL_VOL_UP               0x01
 #define        BT_VCS_UNMUTE_REL_VOL_DOWN      0x02
@@ -591,6 +722,8 @@ static uint8_t vcs_mute(struct bt_vcs *vcs, struct bt_vcp *vcp,
 #define        BT_VCS_UNMUTE                   0x05
 #define        BT_VCS_MUTE                     0x06
 
+#define BT_VOCS_SET_VOL_OFFSET 0x01
+
 #define VCS_OP(_str, _op, _size, _func) \
        { \
                .str = _str, \
@@ -623,6 +756,26 @@ struct vcs_op_handler {
        {}
 };
 
+#define VOCS_OP(_str, _op, _size, _func) \
+       { \
+               .str = _str, \
+               .op = _op, \
+               .size = _size, \
+               .func = _func, \
+       }
+
+struct vocs_op_handler {
+       const char *str;
+       uint8_t op;
+       size_t  size;
+       uint8_t (*func)(struct bt_vocs *vocs, struct bt_vcp *vcp,
+                       struct iovec *iov);
+} vocp_handlers[] = {
+       VOCS_OP("Set Volume Offset", BT_VOCS_SET_VOL_OFFSET,
+               sizeof(uint8_t), vocs_set_vol_offset),
+       {}
+};
+
 static void vcs_cp_write(struct gatt_db_attribute *attrib,
                                unsigned int id, uint16_t offset,
                                const uint8_t *value, size_t len,
@@ -683,6 +836,66 @@ respond:
        gatt_db_attribute_write_result(attrib, id, ret);
 }
 
+static void vocs_cp_write(struct gatt_db_attribute *attrib,
+                               unsigned int id, uint16_t offset,
+                               const uint8_t *value, size_t len,
+                               uint8_t opcode, struct bt_att *att,
+                               void *user_data)
+{
+       struct bt_vocs *vocs = user_data;
+       struct bt_vcp *vcp = vcp_get_session(att, vocs->vdb->db);
+       struct iovec iov = {
+               .iov_base = (void *) value,
+               .iov_len = len,
+       };
+       uint8_t *vcp_op;
+       struct vocs_op_handler *handler;
+       uint8_t ret = BT_ATT_ERROR_REQUEST_NOT_SUPPORTED;
+
+       DBG(vcp, "VOCP Control Point Write");
+
+       if (offset) {
+               DBG(vcp, "invalid offset %d", offset);
+               ret = BT_ATT_ERROR_INVALID_OFFSET;
+               goto respond;
+       }
+
+       if (len < sizeof(*vcp_op)) {
+               DBG(vcp, "invalid len %ld < %ld sizeof(*param)", len,
+                                                       sizeof(*vcp_op));
+               ret = BT_ATT_ERROR_INVALID_ATTRIBUTE_VALUE_LEN;
+               goto respond;
+       }
+
+       vcp_op = iov_pull_mem(&iov, sizeof(*vcp_op));
+
+       for (handler = vocp_handlers; handler && handler->str; handler++) {
+               if (handler->op != *vcp_op)
+                       continue;
+
+               if (iov.iov_len < handler->size) {
+                       DBG(vcp, "invalid len %ld < %ld handler->size", len,
+                           handler->size);
+                       ret = BT_ATT_ERROR_OPCODE_NOT_SUPPORTED;
+                       goto respond;
+               }
+
+               break;
+       }
+
+       if (handler && handler->str) {
+               DBG(vcp, "%s", handler->str);
+
+               ret = handler->func(vocs, vcp, &iov);
+       } else {
+               DBG(vcp, "Unknown opcode 0x%02x", *vcp_op);
+               ret = BT_ATT_ERROR_OPCODE_NOT_SUPPORTED;
+       }
+
+respond:
+       gatt_db_attribute_write_result(attrib, id, ret);
+}
+
 static void vcs_state_read(struct gatt_db_attribute *attrib,
                                unsigned int id, uint16_t offset,
                                uint8_t opcode, struct bt_att *att,
@@ -698,6 +911,21 @@ static void vcs_state_read(struct gatt_db_attribute *attrib,
                                                        iov.iov_len);
 }
 
+static void vocs_state_read(struct gatt_db_attribute *attrib,
+                               unsigned int id, uint16_t offset,
+                               uint8_t opcode, struct bt_att *att,
+                               void *user_data)
+{
+       struct bt_vocs *vocs = user_data;
+       struct iovec iov;
+
+       iov.iov_base = vocs->vostate;
+       iov.iov_len = sizeof(*vocs->vostate);
+
+       gatt_db_attribute_read_result(attrib, id, 0, iov.iov_base,
+                                                       iov.iov_len);
+}
+
 static void vcs_flag_read(struct gatt_db_attribute *attrib,
                                unsigned int id, uint16_t offset,
                                uint8_t opcode, struct bt_att *att,
@@ -713,6 +941,36 @@ static void vcs_flag_read(struct gatt_db_attribute *attrib,
                                                        iov.iov_len);
 }
 
+static void vocs_voal_read(struct gatt_db_attribute *attrib,
+                               unsigned int id, uint16_t offset,
+                               uint8_t opcode, struct bt_att *att,
+                               void *user_data)
+{
+       struct bt_vocs *vocs = user_data;
+       struct iovec iov;
+
+       iov.iov_base = &vocs->vocs_audio_loc;
+       iov.iov_len = sizeof(vocs->vocs_audio_loc);
+
+       gatt_db_attribute_read_result(attrib, id, 0, iov.iov_base,
+                                                       iov.iov_len);
+}
+
+static void vocs_voaodec_read(struct gatt_db_attribute *attrib,
+                               unsigned int id, uint16_t offset,
+                               uint8_t opcode, struct bt_att *att,
+                               void *user_data)
+{
+       struct bt_vocs *vocs = user_data;
+       struct iovec iov;
+
+       iov.iov_base = &vocs->vocs_ao_dec;
+       iov.iov_len = strlen(vocs->vocs_ao_dec);
+
+       gatt_db_attribute_read_result(attrib, id, 0, iov.iov_base,
+                                                       iov.iov_len);
+}
+
 static struct bt_vcs *vcs_new(struct gatt_db *db)
 {
        struct bt_vcs *vcs;
@@ -771,6 +1029,74 @@ static struct bt_vcs *vcs_new(struct gatt_db *db)
        return vcs;
 }
 
+static struct bt_vocs *vocs_new(struct gatt_db *db)
+{
+       struct bt_vocs *vocs;
+       struct vol_offset_state *vostate;
+       bt_uuid_t uuid;
+
+       if (!db)
+               return NULL;
+
+       vocs = new0(struct bt_vocs, 1);
+
+       vostate = new0(struct vol_offset_state, 1);
+
+       vocs->vostate = vostate;
+       vocs->vocs_audio_loc = BT_VCP_FRONT_LEFT;
+       vocs->vocs_ao_dec = "Left Speaker";
+
+       /* Populate DB with VOCS attributes */
+       bt_uuid16_create(&uuid, VOL_OFFSET_CS_UUID);
+       vocs->service = gatt_db_add_service(db, &uuid, true, 9);
+
+       bt_uuid16_create(&uuid, VOCS_STATE_CHAR_UUID);
+       vocs->vos = gatt_db_service_add_characteristic(vocs->service,
+                                       &uuid,
+                                       BT_ATT_PERM_READ,
+                                       BT_GATT_CHRC_PROP_READ |
+                                       BT_GATT_CHRC_PROP_NOTIFY,
+                                       vocs_state_read, NULL,
+                                       vocs);
+
+       vocs->vos_ccc = gatt_db_service_add_ccc(vocs->service,
+                                       BT_ATT_PERM_READ | BT_ATT_PERM_WRITE);
+
+       bt_uuid16_create(&uuid, VOCS_AUDIO_LOC_CHRC_UUID);
+       vocs->voal = gatt_db_service_add_characteristic(vocs->service,
+                                       &uuid,
+                                       BT_ATT_PERM_READ,
+                                       BT_GATT_CHRC_PROP_READ |
+                                       BT_GATT_CHRC_PROP_NOTIFY,
+                                       vocs_voal_read, NULL,
+                                       vocs);
+
+       vocs->voal_ccc = gatt_db_service_add_ccc(vocs->service,
+                                       BT_ATT_PERM_READ | BT_ATT_PERM_WRITE);
+
+       bt_uuid16_create(&uuid, VOCS_CP_CHRC_UUID);
+       vocs->vo_cp = gatt_db_service_add_characteristic(vocs->service,
+                                       &uuid,
+                                       BT_ATT_PERM_WRITE,
+                                       BT_GATT_CHRC_PROP_WRITE,
+                                       NULL, vocs_cp_write,
+                                       vocs);
+
+       bt_uuid16_create(&uuid, VOCS_AUDIO_OP_DESC_CHAR_UUID);
+       vocs->voaodec = gatt_db_service_add_characteristic(vocs->service,
+                                       &uuid,
+                                       BT_ATT_PERM_READ,
+                                       BT_GATT_CHRC_PROP_READ |
+                                       BT_GATT_CHRC_PROP_NOTIFY,
+                                       vocs_voaodec_read, NULL,
+                                       vocs);
+
+       vocs->voaodec_ccc = gatt_db_service_add_ccc(vocs->service,
+                                       BT_ATT_PERM_READ | BT_ATT_PERM_WRITE);
+
+       return vocs;
+}
+
 static struct bt_vcp_db *vcp_db_new(struct gatt_db *db)
 {
        struct bt_vcp_db *vdb;
@@ -787,6 +1113,9 @@ static struct bt_vcp_db *vcp_db_new(struct gatt_db *db)
        vdb->vcs = vcs_new(db);
        vdb->vcs->vdb = vdb;
 
+       vdb->vocs = vocs_new(db);
+       vdb->vocs->vdb = vdb;
+
        queue_push_tail(vcp_db, vdb);
 
        return vdb;
@@ -911,6 +1240,47 @@ static void vcp_vstate_notify(struct bt_vcp *vcp, uint16_t value_handle,
        DBG(vcp, "Vol Counter 0x%x", vstate.counter);
 }
 
+static void vcp_voffset_state_notify(struct bt_vcp *vcp, uint16_t value_handle,
+                               const uint8_t *value, uint16_t length,
+                               void *user_data)
+{
+       struct vol_offset_state vostate;
+
+       memcpy(&vostate, value, sizeof(struct vol_offset_state));
+
+       DBG(vcp, "Vol Offset 0x%x", vostate.vol_offset);
+       DBG(vcp, "Vol Offset Counter 0x%x", vostate.counter);
+}
+
+static void vcp_audio_loc_notify(struct bt_vcp *vcp, uint16_t value_handle,
+                               const uint8_t *value, uint16_t length,
+                               void *user_data)
+{
+       uint32_t *vocs_audio_loc_n = malloc(sizeof(uint32_t));
+       *vocs_audio_loc_n = 0;
+
+       if (value != NULL)
+               memcpy(vocs_audio_loc_n, value, sizeof(uint32_t));
+
+       DBG(vcp, "VOCS Audio Location 0x%x", *vocs_audio_loc_n);
+
+       free(vocs_audio_loc_n);
+}
+
+
+static void vcp_audio_descriptor_notify(struct bt_vcp *vcp,
+                                       uint16_t value_handle,
+                                       const uint8_t *value,
+                                       uint16_t length,
+                                       void *user_data)
+{
+       char vocs_audio_dec_n[256] = {'\0'};
+
+       memcpy(vocs_audio_dec_n, value, length);
+
+       DBG(vcp, "VOCS Audio Descriptor 0x%s", *vocs_audio_dec_n);
+}
+
 static void vcp_vflag_notify(struct bt_vcp *vcp, uint16_t value_handle,
                             const uint8_t *value, uint16_t length,
                             void *user_data)
@@ -972,6 +1342,86 @@ static void read_vol_state(struct bt_vcp *vcp, bool success, uint8_t att_ecode,
        DBG(vcp, "Vol Counter:%x", vs->counter);
 }
 
+static void read_vol_offset_state(struct bt_vcp *vcp, bool success,
+                                 uint8_t att_ecode,
+                                 const uint8_t *value, uint16_t length,
+                                 void *user_data)
+{
+       struct vol_offset_state *vos;
+       struct iovec iov = {
+               .iov_base = (void *) value,
+               .iov_len = length,
+       };
+
+       if (!success) {
+               DBG(vcp, "Unable to read Vol Offset State: error 0x%02x",
+                   att_ecode);
+               return;
+       }
+
+       vos = iov_pull_mem(&iov, sizeof(*vos));
+       if (!vos) {
+               DBG(vcp, "Unable to get Vol Offset State");
+               return;
+       }
+
+       DBG(vcp, "Vol Set:%x", vos->vol_offset);
+       DBG(vcp, "Vol Counter:%x", vos->counter);
+}
+
+static void read_vocs_audio_location(struct bt_vcp *vcp, bool success,
+                                    uint8_t att_ecode,
+                                    const uint8_t *value, uint16_t length,
+                                    void *user_data)
+{
+       uint32_t *vocs_audio_loc;
+       struct iovec iov = {
+               .iov_base = (void *) value,
+               .iov_len = length,
+       };
+
+       if (!success) {
+               DBG(vcp, "Unable to read VOCS Audio Location: error 0x%02x",
+                   att_ecode);
+               return;
+       }
+
+       vocs_audio_loc = iov_pull_mem(&iov, sizeof(uint32_t));
+       if (!*vocs_audio_loc) {
+               DBG(vcp, "Unable to get VOCS Audio Location");
+               return;
+       }
+
+       DBG(vcp, "VOCS Audio Loc:%x", *vocs_audio_loc);
+}
+
+
+static void read_vocs_audio_descriptor(struct bt_vcp *vcp, bool success,
+                                      uint8_t att_ecode,
+                                      const uint8_t *value, uint16_t length,
+                                      void *user_data)
+{
+       char *vocs_ao_dec_r;
+       struct iovec iov = {
+               .iov_base = (void *) value,
+               .iov_len = length,
+       };
+
+       if (!success) {
+               DBG(vcp, "Unable to read VOCS Audio Descriptor: error 0x%02x",
+                       att_ecode);
+               return;
+       }
+
+       vocs_ao_dec_r = iov_pull_mem(&iov, length);
+       if (!*vocs_ao_dec_r) {
+               DBG(vcp, "Unable to get VOCS Audio Descriptor");
+               return;
+       }
+
+       DBG(vcp, "VOCS Audio Descriptor:%s", *vocs_ao_dec_r);
+}
+
 static void vcp_pending_destroy(void *data)
 {
        struct bt_vcp_pending *pending = data;
@@ -1128,6 +1578,90 @@ static void foreach_vcs_char(struct gatt_db_attribute *attr, void *user_data)
        }
 }
 
+static void foreach_vocs_char(struct gatt_db_attribute *attr, void *user_data)
+{
+       struct bt_vcp *vcp = user_data;
+       uint16_t value_handle;
+       bt_uuid_t uuid, uuid_vostate, uuid_audio_loc, uuid_vo_cp,
+                       uuid_audio_op_decs;
+       struct bt_vocs *vocs;
+
+       if (!gatt_db_attribute_get_char_data(attr, NULL, &value_handle,
+                                               NULL, NULL, &uuid))
+               return;
+
+       bt_uuid16_create(&uuid_vostate, VOCS_STATE_CHAR_UUID);
+       bt_uuid16_create(&uuid_audio_loc, VOCS_AUDIO_LOC_CHRC_UUID);
+       bt_uuid16_create(&uuid_vo_cp, VOCS_CP_CHRC_UUID);
+       bt_uuid16_create(&uuid_audio_op_decs, VOCS_AUDIO_OP_DESC_CHAR_UUID);
+
+       if (!bt_uuid_cmp(&uuid, &uuid_vostate)) {
+               DBG(vcp, "VOCS Vol state found: handle 0x%04x", value_handle);
+
+               vocs = vcp_get_vocs(vcp);
+               if (!vocs || vocs->vos)
+                       return;
+
+               vocs->vos = attr;
+
+               vcp_read_value(vcp, value_handle, read_vol_offset_state, vcp);
+
+               vcp->state_id = vcp_register_notify(vcp, value_handle,
+                                       vcp_voffset_state_notify, NULL);
+
+               return;
+       }
+
+       if (!bt_uuid_cmp(&uuid, &uuid_audio_loc)) {
+               DBG(vcp, "VOCS Volume Audio Location found: handle 0x%04x",
+                       value_handle);
+
+               vocs = vcp_get_vocs(vcp);
+               if (!vocs || vocs->voal)
+                       return;
+
+               vocs->voal = attr;
+
+               vcp_read_value(vcp, value_handle, read_vocs_audio_location,
+                                      vcp);
+
+               vcp->audio_loc_id = vcp_register_notify(vcp, value_handle,
+                                               vcp_audio_loc_notify, NULL);
+
+               return;
+       }
+
+       if (!bt_uuid_cmp(&uuid, &uuid_vo_cp)) {
+               DBG(vcp, "VOCS Volume CP found: handle 0x%04x", value_handle);
+
+               vocs = vcp_get_vocs(vcp);
+               if (!vocs || vocs->vo_cp)
+                       return;
+
+               vocs->vo_cp = attr;
+
+               return;
+       }
+
+       if (!bt_uuid_cmp(&uuid, &uuid_audio_op_decs)) {
+               DBG(vcp, "VOCS Vol Audio Descriptor found: handle 0x%04x",
+                       value_handle);
+
+               vocs = vcp_get_vocs(vcp);
+               if (!vocs || vocs->voaodec)
+                       return;
+
+               vocs->voaodec = attr;
+
+               vcp_read_value(vcp, value_handle, read_vocs_audio_descriptor,
+                              vcp);
+               vcp->ao_dec_id = vcp_register_notify(vcp, value_handle,
+                                       vcp_audio_descriptor_notify, NULL);
+
+       }
+
+}
+
 static void foreach_vcs_service(struct gatt_db_attribute *attr,
                                                void *user_data)
 {
@@ -1141,6 +1675,19 @@ static void foreach_vcs_service(struct gatt_db_attribute *attr,
        gatt_db_service_foreach_char(attr, foreach_vcs_char, vcp);
 }
 
+static void foreach_vocs_service(struct gatt_db_attribute *attr,
+                                               void *user_data)
+{
+       struct bt_vcp *vcp = user_data;
+       struct bt_vocs *vocs = vcp_get_vocs(vcp);
+
+       vocs->service = attr;
+
+       gatt_db_service_set_claimed(attr, true);
+
+       gatt_db_service_foreach_char(attr, foreach_vocs_char, vcp);
+}
+
 bool bt_vcp_attach(struct bt_vcp *vcp, struct bt_gatt_client *client)
 {
        bt_uuid_t uuid;
@@ -1163,5 +1710,8 @@ bool bt_vcp_attach(struct bt_vcp *vcp, struct bt_gatt_client *client)
        bt_uuid16_create(&uuid, VCS_UUID);
        gatt_db_foreach_service(vcp->ldb->db, &uuid, foreach_vcs_service, vcp);
 
+       bt_uuid16_create(&uuid, VOL_OFFSET_CS_UUID);
+       gatt_db_foreach_service(vcp->ldb->db, &uuid, foreach_vocs_service, vcp);
+
        return true;
 }