Memory Technology Device Drivers

• include/nuttx/mtd/mtd.h. All structures and APIs needed to work with MTD drivers are provided in this header file.

• struct mtd_dev_s. Each MTD device driver must implement an instance of struct mtd_dev_s. That structure defines a call table with the following methods:

  Erase the specified erase blocks (units are erase blocks):

  Read/write from the specified read/write blocks:

  Some devices may support byte oriented reads (optional). Most MTD devices are inherently block oriented so byte-oriented accesses are not supported. It is recommended that low-level drivers not support read() if it requires buffering.

  Some devices may also support byte oriented writes (optional). Most MTD devices are inherently block oriented so byte-oriented accesses are not supported. It is recommended that low-level drivers not support read() if it requires buffering. This interface is only available if CONFIG_MTD_BYTE_WRITE is defined.

  Support other, less frequently used commands:

  • MTDIOC_GEOMETRY: Get MTD geometry

  • MTDIOC_XIPBASE:: Convert block to physical address for eXecute-In-Place

  • MTDIOC_BULKERASE: Erase the entire device

  is provided via a single ioctl method (see include/nuttx/fs/ioctl.h):

• Binding MTD Drivers. MTD drivers are not normally directly accessed by user code, but are usually bound to another, higher level device driver. In general, the binding sequence is:

  1. Get an instance of struct mtd_dev_s from the hardware-specific MTD device driver, and

  2. Provide that instance to the initialization method of the higher level device driver.

• Examples: drivers/mtd/m25px.c and drivers/mtd/ftl.c