Function esp_ota_begin 

pub unsafe extern "C" fn esp_ota_begin(
    partition: *const esp_partition_t,
    image_size: usize,
    out_handle: *mut esp_ota_handle_t,
) -> esp_err_t

@brief Commence an OTA update writing to the specified partition.

The specified partition is erased to the specified image size.

If image size is not yet known, pass OTA_SIZE_UNKNOWN which will cause the entire partition to be erased.

On success, this function allocates memory that remains in use until esp_ota_end() is called with the returned handle.

Note: If the rollback option is enabled and the running application has the ESP_OTA_IMG_PENDING_VERIFY state then it will lead to the ESP_ERR_OTA_ROLLBACK_INVALID_STATE error. Confirm the running app before to run download a new app, use esp_ota_mark_app_valid_cancel_rollback() function for it (this should be done as early as possible when you first download a new application).

Note: Rollback is applicable only for app type partitions. Note: For Rollback - The OTA data slot corresponding to the last boot application partition will be invalidated.

@param partition Pointer to info for partition which will receive the OTA update. Required. This is considered as the staging partition (where OTA is downloaded), be default this also considered as the final partition which supposed to be updated. The final partition can be overwritten using esp_ota_set_final_partition() after calling esp_ota_begin() to relocate contents to the final destination partition. @param image_size Size of new OTA app image. Partition will be erased in order to receive this size of image. If 0 or OTA_SIZE_UNKNOWN, the entire partition is erased. @param out_handle On success, returns a handle which should be used for subsequent esp_ota_write() and esp_ota_end() calls.

@return

• ESP_OK: OTA operation commenced successfully.
• ESP_ERR_INVALID_ARG: partition or out_handle arguments were NULL, or partition doesn’t point to an OTA app partition.
• ESP_ERR_NO_MEM: Cannot allocate memory for OTA operation.
• ESP_ERR_OTA_PARTITION_CONFLICT: Partition holds the currently running firmware, cannot update in place.
• ESP_ERR_NOT_FOUND: Partition argument not found in partition table.
• ESP_ERR_OTA_SELECT_INFO_INVALID: The OTA data partition contains invalid data.
• ESP_ERR_INVALID_SIZE: Partition doesn’t fit in configured flash size.
• ESP_ERR_FLASH_OP_TIMEOUT or ESP_ERR_FLASH_OP_FAIL: Flash write failed.
• ESP_ERR_OTA_ROLLBACK_INVALID_STATE: If the running app has not confirmed state. Before performing an update, the application must be valid.