To fully take advantage of advanced peripherals (for example, NAND flash controllers), you might decide to provide your own implementation of the controller layer. The controller layer is one level above the BSP layer. Its interface is more flexible, but is also more complex to implement. If you choose that route, it is strongly recommended to use the provided implementations as an example. Listing 15-12 describes The listing below describes the API that must be implemented for the controller layer.Listing 15-12 Controller API type definition
Before implementing the following functions, it is important to understand the difference between out-of-sector (OOS) data and the spare area. In a NAND device, each page has a spare area, typically used to store metadata and error correction codes (ECC). The spare area also contains a factory defect mark and, optionally, reserved sections. In the implementation of the µC/FS NAND driver, the OOS data is metadata sent to the controller layer by the translation layer. It must be stored in the spare area, wit.hout overwriting the bad block mark and without writing to the reserved section. It must also be protected by ECC. The OOS data is only a part of what is inside the spare area. It doesn’t include the factory defect marks, the reserved sections and the ECC data. Also, if the sector size is not equal to the page size, the OOS data will be associated to a single sector, while the spare area will be associated to a single page. In that case, multiple OOS sections would be fit in a single spare area.
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