I am trying to implement Attribute caching as described in Vol 3, part G, section 2.5.2 of the Bluetooth Core Spec.
- Reading the GATT Database Hash seems to work:
- The bt_gatt_read returns zero
- The callback function returns a zero “err” parameter
- However:
- the callback also returns a “length” of 3 (I would expect a 1 (if the return is a “field”) or a 16 (if the return is an array of bytes))
- the bytes are not what I would expect – they don’t match my reference db hash.
- an Ellisys trace does not show the Read by UUID ATT Transaction I would expect
- I expect I am not configuring the bt_gatt_read_params correctly - here's the relevant code snippet:
// Callback for GATT DB Hash read
static uint8_t unicast_client_read_func_cb(struct bt_conn *conn, uint8_t err,
struct bt_gatt_read_params *read, const void *data,
uint16_t length)
{
LOG_INF("TEC - unicast_client_read_func_cb: conn %p err %u read %p data 0x%032x length 0x%02x\n",
(void *)conn, err, (void *)read, data, length);
for (int i = 0; i < 32; i++) {
LOG_INF("TEC - unicast_client_read_func_cb: data[%0d] = 0x%02x", i, ((uint8_t *)data)[i]);
}
return BT_GATT_ITER_STOP;
}
int unicast_client_gatt_db_hash_read(struct bt_conn *conn)
{
LOG_INF("TEC - unicast_client_gatt_db_hash_read: conn %p\n", (void *)conn);
int ret;
struct stream_index idx;
static struct bt_gatt_read_params read_params;
struct bt_gatt_read_params* read_params_ptr = &read_params;
ret = device_index_get(conn, &idx);
LOG_INF("TEC - device_index_get ret %d idx %d,%d,%d\n", ret, idx.lvl1, idx.lvl2, idx.lvl3);
if (ret) {
return ret;
}
(*read_params_ptr).func = unicast_client_read_func_cb;
(*read_params_ptr).by_uuid.uuid = BT_UUID_GATT_DB_HASH_VAL; // GATT DB Hash UUID
(*read_params_ptr).by_uuid.start_handle = 0x0001;
(*read_params_ptr).by_uuid.end_handle = 0xffff;
(*read_params_ptr).handle_count = 0;
ret = bt_gatt_read(conn, read_params_ptr);
if (ret) {
LOG_WRN("Failed to read gatt db hash: %d", ret);
return ret;
}
return 0;
}
