/**
 * @file
 *
 * @ingroup RTEMSFDisk
 *
 * @brief Interface to a Flash Disk Block Device
 *
 * This file defines the interface to a flash disk block device.
 */

/*
 * Copyright (C) 2007 Chris Johns
 *
 * The license and distribution terms for this file may be
 * found in the file LICENSE in this distribution or at
 * http://www.rtems.org/license/LICENSE.
 */

#if !defined (_RTEMS_FLASHDISK_H_)
#define _RTEMS_FLASHDISK_H_

#include <stdint.h>
#include <sys/ioctl.h>

#include <rtems.h>

/**
 * @defgroup RTEMSFDisk Flash Disk Device
 *
 * @ingroup rtems_blkdev
 *
 * Flash disk driver for RTEMS provides support for block based
 * file systems on flash devices. The driver is not a flash file
 * system nor does it try to compete with flash file systems. It
 * currently does not journal how-ever block sequence numbering
 * could be added to allow recovery of a past positions if
 * a power down occurred while being updated.
 *
 * This flash driver provides block device support for most flash
 * devices. The driver has been tested on NOR type devices such
 * as the AMLV160 or M28W160. Support for NAND type devices may
 * require driver changes to allow speedy recover of the block
 * mapping data and to also handle the current use of word programming.
 * Currently the page descriptors are stored in the first few pages
 * of each segment.
 *
 * The driver supports devices, segments and pages. You provide
 * to the driver the device descriptions as a table of device
 * descriptors. Each device descriptor contain a table of
 * segment descriptions or segment descriptors. The driver uses
 * this information to manage the devices.
 *
 * A device is made up of segments. These are also called
 * sectors or blocks. It is the smallest erasable part of a device.
 * A device can have differing size segments at different
 * offsets in the device. The segment descriptors support repeating
 * segments that are continuous in the device. The driver breaks the
 * segments up into pages. The first pages of a segment contain
 * the page descriptors. A page descriptor hold the page flags,
 * a CRC for the page of data and the block number the page
 * holds. The block can appear in any order in the devices. A
 * page is active if it hold a current block of data. If the
 * used bit is set the page is counted as used. A page moves
 * from erased to active to used then back to erased. If a block
 * is written that is already in a page, the block is written to
 * a new page the old page is flagged as used.
 *
 * At initialization time each segment's page descriptors are
 * read into memory and scanned to determine the active pages,
 * the used pages and the bad pages. If a segment has any erased
 * pages it is queue on the available queue. If the segment has
 * no erased pages it is queue on the used queue.
 *
 * The available queue is sorted from the least number available
 * to the most number of available pages. A segment that has just
 * been erased will placed at the end of the queue. A segment that
 * has only a few available pages will be used sooner and once
 * there are no available pages it is queued on the used queue.
 * The used queue hold segments that have no available pages and
 * is sorted from the least number of active pages to the most
 * number of active pages.
 *
 * The driver is required to compact segments. Compacting takes
 * the segment with the most number of available pages from the
 * available queue then takes segments with the least number of
 * active pages from the used queue until it has enough pages
 * to fill the empty segment. As the active pages are moved
 * they flagged as used and once the segment has only used pages
 * it is erased.
 *
 * A flash block driver like this never knows if a page is not
 * being used by the file-system. A typical file system is not
 * design with the idea of erasing a block on a disk once it is
 * not being used. The file-system will normally use a flag
 * or a location as a marker to say that part of the disk is
 * no longer in use. This means a number of blocks could be
 * held in active pages but are no in use by the file system.
 * The file system may also read blocks that have never been
 * written to disk. This complicates the driver and may make
 * the wear, usage and erase patterns harsher than a flash
 * file system. The driver may also suffer from problems if
 * power is lost.
 *
 * There are some flash disk specific IO control request types.
 * To use open the device and issue the ioctl() call.
 *
 * @code
 *  int fd = open ("/dev/flashdisk0", O_WRONLY, 0);
 *  if (fd < 0)
 *  {
 *    printf ("driver open failed: %s\n", strerror (errno));
 *    exit (1);
 *  }
 *  if (ioctl (fd, RTEMS_FDISK_IOCTL_ERASE_DISK) < 0)
 *  {
 *    printf ("driver erase failed: %s\n", strerror (errno));
 *    exit (1);
 *  }
 *  close (fd);
 * @endcode
 */
/**@{**/

/**
 * @brief The base name of the flash disks.
 */
#define RTEMS_FLASHDISK_DEVICE_BASE_NAME "/dev/fdd"

#define RTEMS_FDISK_IOCTL_ERASE_DISK   _IO('B', 128)
#define RTEMS_FDISK_IOCTL_COMPACT      _IO('B', 129)
#define RTEMS_FDISK_IOCTL_ERASE_USED   _IO('B', 130)
#define RTEMS_FDISK_IOCTL_MONITORING   _IO('B', 131)
#define RTEMS_FDISK_IOCTL_INFO_LEVEL   _IO('B', 132)
#define RTEMS_FDISK_IOCTL_PRINT_STATUS _IO('B', 133)

/**
 * @brief Flash Disk Monitoring Data allows a user to obtain
 * the current status of the disk.
 */
typedef struct rtems_fdisk_monitor_data
{
  uint32_t block_size;
  uint32_t block_count;
  uint32_t unavail_blocks;
  uint32_t device_count;
  uint32_t segment_count;
  uint32_t page_count;
  uint32_t blocks_used;
  uint32_t segs_available;
  uint32_t segs_used;
  uint32_t segs_failed;
  uint32_t seg_erases;
  uint32_t pages_desc;
  uint32_t pages_active;
  uint32_t pages_used;
  uint32_t pages_bad;
  uint32_t info_level;
} rtems_fdisk_monitor_data;

/**
 * @brief Flash Segment Descriptor holds, number of continuous segments in the
 * device of this type, the base segment number in the device, the address
 * offset of the base segment in the device, and the size of segment.
 *
 * Typically this structure is part of a table of segments in the
 * device which is referenced in the flash disk configuration table.
 * The reference is kept in the driver and used all the time to
 * manage the flash device, therefore it must always exist.
 */
typedef struct rtems_fdisk_segment_desc
{
  uint16_t count;    /**< Number of segments of this type in a row. */
  uint16_t segment;  /**< The base segment number. */
  uint32_t offset;   /**< Address offset of base segment in device. */
  uint32_t size;     /**< Size of the segment in bytes. */
} rtems_fdisk_segment_desc;

/**
 * @brief Return the number of kilo-bytes.
 */
#define RTEMS_FDISK_KBYTES(_k) (UINT32_C(1024) * (_k))

/**
 * Forward declaration of the device descriptor.
 */
struct rtems_fdisk_device_desc;

/**
 * @brief Flash Low Level driver handlers.
 *
 * Typically this structure is part of a table of handlers in the
 * device which is referenced in the flash disk configuration table.
 * The reference is kept in the driver and used all the time to
 * manage the flash device, therefore it must always exist.
 */
typedef struct rtems_fdisk_driver_handlers
{
  /**
   * Read data from the device into the buffer. Return an errno
   * error number if the device cannot be read. A segment descriptor
   * can describe more than one segment in a device if the device has
   * repeating segments. The segment number is the device segment to
   * access and the segment descriptor must reference the segment
   * being requested. For example the segment number must resided in
   * the range [base, base + count).
   *
   * @param sd The segment descriptor.
   * @param device The device to read data from.
   * @param segment The segment within the device to read.
   * @param offset The offset in the segment to read.
   * @param buffer The buffer to read the data into.
   * @param size The amount of data to read.
   * @retval 0 No error.
   * @retval EIO The read did not complete.
   */
  int (*read) (const rtems_fdisk_segment_desc* sd,
               uint32_t                        device,
               uint32_t                        segment,
               uint32_t                        offset,
               void*                           buffer,
               uint32_t                        size);

  /**
   * Write data from the buffer to the device. Return an errno
   * error number if the device cannot be written to. A segment
   * descriptor can describe more than segment in a device if the
   * device has repeating segments. The segment number is the device
   * segment to access and the segment descriptor must reference
   * the segment being requested. For example the segment number must
   * resided in the range [base, base + count).
   *
   * @param sd The segment descriptor.
   * @param device The device to write data from.
   * @param segment The segment within the device to write to.
   * @param offset The offset in the segment to write.
   * @param buffer The buffer to write the data from.
   * @param size The amount of data to write.
   * @retval 0 No error.
   * @retval EIO The write did not complete or verify.
   */
  int (*write) (const rtems_fdisk_segment_desc* sd,
                uint32_t                        device,
                uint32_t                        segment,
                uint32_t                        offset,
                const void*                     buffer,
                uint32_t                        size);

  /**
   * Blank a segment in the device. Return an errno error number
   * if the device cannot be read or is not blank. A segment descriptor
   * can describe more than segment in a device if the device has
   * repeating segments. The segment number is the device segment to
   * access and the segment descriptor must reference the segment
   * being requested. For example the segment number must resided in
   * the range [base, base + count).
   *
   * @param sd The segment descriptor.
   * @param device The device to read data from.
   * @param segment The segment within the device to read.
   * @param offset The offset in the segment to checl.
   * @param size The amount of data to check.
   * @retval 0 No error.
   * @retval EIO The segment is not blank.
   */
  int (*blank) (const rtems_fdisk_segment_desc* sd,
                uint32_t                        device,
                uint32_t                        segment,
                uint32_t                        offset,
                uint32_t                        size);

  /**
   * Verify data in the buffer to the data in the device. Return an
   * errno error number if the device cannot be read. A segment
   * descriptor can describe more than segment in a device if the
   * device has repeating segments. The segment number is the
   * segment to access and the segment descriptor must reference
   * the device segment being requested. For example the segment number
   * must resided in the range [base, base + count).
   *
   * @param sd The segment descriptor.
   * @param device The device to verify data in.
   * @param segment The segment within the device to verify.
   * @param offset The offset in the segment to verify.
   * @param buffer The buffer to verify the data in the device with.
   * @param size The amount of data to verify.
   * @retval 0 No error.
   * @retval EIO The data did not verify.
   */
  int (*verify) (const rtems_fdisk_segment_desc* sd,
                 uint32_t                        device,
                 uint32_t                        segment,
                 uint32_t                        offset,
                 const void*                     buffer,
                 uint32_t                        size);

  /**
   * Erase the segment. Return an errno error number if the
   * segment cannot be erased. A segment descriptor can describe
   * more than segment in a device if the device has repeating
   * segments. The segment number is the device segment to access and
   * the segment descriptor must reference the segment being requested.
   *
   * @param sd The segment descriptor.
   * @param device The device to erase the segment of.
   * @param segment The segment within the device to erase.
   * @retval 0 No error.
   * @retval EIO The segment was not erased.
   */
  int (*erase) (const rtems_fdisk_segment_desc* sd,
                uint32_t                        device,
                uint32_t                        segment);

  /**
   * Erase the device. Return an errno error number if the
   * segment cannot be erased. A segment descriptor can describe
   * more than segment in a device if the device has repeating
   * segments. The segment number is the segment to access and
   * the segment descriptor must reference the segment being requested.
   *
   * @param sd The segment descriptor.
   * @param device The device to erase.
   * @retval 0 No error.
   * @retval EIO The device was not erased.
   */
  int (*erase_device) (const struct rtems_fdisk_device_desc* dd,
                       uint32_t                              device);

} rtems_fdisk_driver_handlers;

/**
 * @brief Flash Device Descriptor holds the segments in a device.
 *
 * The placing of the segments in a device decriptor allows the low level
 * driver to share the segment descriptors for a number of devices.
 *
 * Typically this structure is part of a table of segments in the
 * device which is referenced in the flash disk configuration table.
 * The reference is kept in the driver and used all the time to
 * manage the flash device, therefore it must always exist.
 */
typedef struct rtems_fdisk_device_desc
{
  uint32_t                           segment_count; /**< Number of segments. */
  const rtems_fdisk_segment_desc*    segments;      /**< Array of segments. */
  const rtems_fdisk_driver_handlers* flash_ops;     /**< Device handlers. */
} rtems_fdisk_device_desc;

/**
 * @brief RTEMS Flash Disk configuration table used to initialise the
 * driver.
 *
 * The unavailable blocks count is the number of blocks less than the
 * available number of blocks the file system is given. This means there
 * will always be that number of blocks available when the file system
 * thinks the disk is full. The compaction code needs blocks to compact
 * with so you will never be able to have all the blocks allocated to the
 * file system and be able to full the disk.
 *
 * The compacting segment count is the number of segments that are
 * moved into a new segment. A high number will mean more segments with
 * low active page counts and high used page counts will be moved into
 * avaliable pages how-ever this extends the compaction time due to
 * time it takes the erase the pages. There is no pont making this number
 * greater than the maximum number of pages in a segment.
 *
 * The available compacting segment count is the level when compaction occurs
 * when writing. If you set this to 0 then compaction will fail because
 * there will be no segments to compact into.
 *
 * The info level can be 0 for off with error, and abort messages allowed.
 * Level 1 is warning messages, level 1 is informational messages, and level 3
 * is debugging type prints. The info level can be turned off with a compile
 * time directive on the command line to the compiler of:
 *
 *     -DRTEMS_FDISK_TRACE=0
 */
typedef struct rtems_flashdisk_config
{
  uint32_t                       block_size;     /**< The block size. */
  uint32_t                       device_count;   /**< The number of devices. */
  const rtems_fdisk_device_desc* devices;        /**< The device descriptions. */
  uint32_t                       flags;          /**< Set of flags to control
                                                      driver. */
  /**
   * Number of blocks not available to the file system.  This number must be
   * greater than or equal to the number of blocks in the largest segment to
   * avoid starvation of erased blocks.
   */
  uint32_t                       unavail_blocks;

  uint32_t                       compact_segs;   /**< Max number of segs to
                                                      compact in one pass. */
  /**
   * The number of segments when compaction occurs when writing.  In case the
   * number of segments in the available queue is less than or equal to this
   * number the compaction process will be triggered.  The available queue
   * contains all segments with erased blocks.
   */
  uint32_t                       avail_compact_segs;
  uint32_t                       info_level;     /**< Default info level. */
} rtems_flashdisk_config;

/*
 * Driver flags.
 */

/**
 * Leave the erasing of used segment to the background handler.
 */
#define RTEMS_FDISK_BACKGROUND_ERASE (1 << 0)

/**
 * Leave the compacting of of used segment to the background handler.
 */
#define RTEMS_FDISK_BACKGROUND_COMPACT (1 << 1)

/**
 * Check the pages during initialisation to see which pages are
 * valid and which are not. This could slow down initialising the
 * disk driver.
 */
#define RTEMS_FDISK_CHECK_PAGES (1 << 2)

/**
 * Blank check the flash device before writing to them. This is needed if
 * you think you have a driver or device problem.
 */
#define RTEMS_FDISK_BLANK_CHECK_BEFORE_WRITE (1 << 3)

/**
 * Flash disk device driver initialization. Place in a table as the
 * initialisation entry and remainder of the entries are the
 * RTEMS block device generic handlers.
 *
 * @param major Flash disk major device number.
 * @param minor Minor device number, not applicable.
 * @param arg Initialization argument, not applicable.
 * @return The rtems_device_driver is actually just
 *         rtems_status_code.
 */
rtems_device_driver
rtems_fdisk_initialize (rtems_device_major_number major,
                        rtems_device_minor_number minor,
                        void*                     arg);

/**
 * @brief External reference to the configuration. Please supply.
 * Support is present in confdefs.h for providing this variable.
 */
extern const rtems_flashdisk_config rtems_flashdisk_configuration[];

/**
 * @brief External reference to the number of configurations. Please supply.
 * Support is present in confdefs.h for providing this variable.
 */
extern uint32_t rtems_flashdisk_configuration_size;

/** @} */

#endif
