ble_gatt_db_srv_t is not aligned

[Daniel]

pm_peer_data_remote_db_store() stores an array of ble_gatt_db_srv_t.

pm_peer_data_remote_db_store() calls pm_peer_data_store(), which requires a buffer whose alignment and size are a multiple of 4 bytes.

ble_gatt_db_srv_t is not declared with alignment:

typedef struct
{
    ble_uuid_t               srv_uuid;                                  /**< UUID of the service. */
    uint8_t                  char_count;                                /**< Number of characteristics present in the service. */
    ble_gattc_handle_range_t handle_range;                              /**< Service Handle Range. */
    ble_gatt_db_char_t       charateristics[BLE_GATT_DB_MAX_CHARS];     /**< Array of information related to the characteristics present in the service. This list can extend further than one. */
} ble_gatt_db_srv_t;

[Petter Myhre]

Are you referring to a specific example?

Can't you do something like

__ALIGN(4) ble_gatt_db_srv_t ble_gatt_db_srv;

?

[Daniel]

---

static __ALIGN(4) ble_gatt_db_srv_t xServiceCache[NUMBER_OF_SERVICE_CACHES];
            
          /* Attempt to load attribute database from flash */
          usLength = sizeof(xServiceCache);
        
          err_code = pm_peer_data_remote_db_load
          (
              p_evt->peer_id,
              xServiceCache,
              &usLength
          );

Returns NRF_ERROR_INVALID_PARAM.

Adding __ALIGN() to the array aligns the array itself, but does not make it a multiple of 4 bytes. Adding __ALIGN() to the type also makes the array a multiple of 4 bytes (since each element of the array must be aligned).

[Daniel]

IDEA: declare a padding uint32_t directly after the array declaration. Round up to the nearest multiple of 4 when calling pm_peer_data_remote_db_load().

Anyone see an issue with this approach?

[Petter Myhre]

I checked with the developers, your suggestion might work, but they suggested the following:

uint8_t gatt_db_buf[ALIGN_NUM(4, sizeof(ble_gatt_db_srv_t)*NUMBER_OF_SERVICE_CACHES)];
ble_gatt_db_srv_t * xServiceCache = (ble_gatt_db_srv_t *) gatt_db_buf;
uint32_t usLength = sizeof(gatt_db_buf);