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name : ubi.h
 /* SPDX-License-Identifier: GPL-2.0-or-later */
/*
 * Copyright (c) International Business Machines Corp., 2006
 *
 * Author: Artem Bityutskiy (Битюцкий Артём)
 */

#ifndef __LINUX_UBI_H__
#define __LINUX_UBI_H__

#include <linux/ioctl.h>
#include <linux/types.h>
#include <linux/scatterlist.h>
#include <mtd/ubi-user.h>

/* All voumes/LEBs */
#define UBI_ALL -1

/*
 * Maximum number of scatter gather list entries,
 * we use only 64 to have a lower memory foot print.
 */
#define UBI_MAX_SG_COUNT 64

/*
 * enum ubi_open_mode - UBI volume open mode constants.
 *
 * UBI_READONLY: read-only mode
 * UBI_READWRITE: read-write mode
 * UBI_EXCLUSIVE: exclusive mode
 * UBI_METAONLY: modify only the volume meta-data,
 *  i.e. the data stored in the volume table, but not in any of volume LEBs.
 */
enum {
	UBI_READONLY = 1,
	UBI_READWRITE,
	UBI_EXCLUSIVE,
	UBI_METAONLY
};

/**
 * struct ubi_volume_info - UBI volume description data structure.
 * @vol_id: volume ID
 * @ubi_num: UBI device number this volume belongs to
 * @size: how many physical eraseblocks are reserved for this volume
 * @used_bytes: how many bytes of data this volume contains
 * @used_ebs: how many physical eraseblocks of this volume actually contain any
 *            data
 * @vol_type: volume type (%UBI_DYNAMIC_VOLUME or %UBI_STATIC_VOLUME)
 * @corrupted: non-zero if the volume is corrupted (static volumes only)
 * @upd_marker: non-zero if the volume has update marker set
 * @alignment: volume alignment
 * @usable_leb_size: how many bytes are available in logical eraseblocks of
 *                   this volume
 * @name_len: volume name length
 * @name: volume name
 * @cdev: UBI volume character device major and minor numbers
 *
 * The @corrupted flag is only relevant to static volumes and is always zero
 * for dynamic ones. This is because UBI does not care about dynamic volume
 * data protection and only cares about protecting static volume data.
 *
 * The @upd_marker flag is set if the volume update operation was interrupted.
 * Before touching the volume data during the update operation, UBI first sets
 * the update marker flag for this volume. If the volume update operation was
 * further interrupted, the update marker indicates this. If the update marker
 * is set, the contents of the volume is certainly damaged and a new volume
 * update operation has to be started.
 *
 * To put it differently, @corrupted and @upd_marker fields have different
 * semantics:
 *     o the @corrupted flag means that this static volume is corrupted for some
 *       reasons, but not because an interrupted volume update
 *     o the @upd_marker field means that the volume is damaged because of an
 *       interrupted update operation.
 *
 * I.e., the @corrupted flag is never set if the @upd_marker flag is set.
 *
 * The @used_bytes and @used_ebs fields are only really needed for static
 * volumes and contain the number of bytes stored in this static volume and how
 * many eraseblock this data occupies. In case of dynamic volumes, the
 * @used_bytes field is equivalent to @size*@usable_leb_size, and the @used_ebs
 * field is equivalent to @size.
 *
 * In general, logical eraseblock size is a property of the UBI device, not
 * of the UBI volume. Indeed, the logical eraseblock size depends on the
 * physical eraseblock size and on how much bytes UBI headers consume. But
 * because of the volume alignment (@alignment), the usable size of logical
 * eraseblocks if a volume may be less. The following equation is true:
 *	@usable_leb_size = LEB size - (LEB size mod @alignment),
 * where LEB size is the logical eraseblock size defined by the UBI device.
 *
 * The alignment is multiple to the minimal flash input/output unit size or %1
 * if all the available space is used.
 *
 * To put this differently, alignment may be considered is a way to change
 * volume logical eraseblock sizes.
 */
struct ubi_volume_info {
	int ubi_num;
	int vol_id;
	int size;
	long long used_bytes;
	int used_ebs;
	int vol_type;
	int corrupted;
	int upd_marker;
	int alignment;
	int usable_leb_size;
	int name_len;
	const char *name;
	dev_t cdev;
	struct device *dev;
};

/**
 * struct ubi_sgl - UBI scatter gather list data structure.
 * @list_pos: current position in @sg[]
 * @page_pos: current position in @sg[@list_pos]
 * @sg: the scatter gather list itself
 *
 * ubi_sgl is a wrapper around a scatter list which keeps track of the
 * current position in the list and the current list item such that
 * it can be used across multiple ubi_leb_read_sg() calls.
 */
struct ubi_sgl {
	int list_pos;
	int page_pos;
	struct scatterlist sg[UBI_MAX_SG_COUNT];
};

/**
 * ubi_sgl_init - initialize an UBI scatter gather list data structure.
 * @usgl: the UBI scatter gather struct itself
 *
 * Please note that you still have to use sg_init_table() or any adequate
 * function to initialize the unterlaying struct scatterlist.
 */
static inline void ubi_sgl_init(struct ubi_sgl *usgl)
{
	usgl->list_pos = 0;
	usgl->page_pos = 0;
}

/**
 * struct ubi_device_info - UBI device description data structure.
 * @ubi_num: ubi device number
 * @leb_size: logical eraseblock size on this UBI device
 * @leb_start: starting offset of logical eraseblocks within physical
 *             eraseblocks
 * @min_io_size: minimal I/O unit size
 * @max_write_size: maximum amount of bytes the underlying flash can write at a
 *                  time (MTD write buffer size)
 * @ro_mode: if this device is in read-only mode
 * @cdev: UBI character device major and minor numbers
 *
 * Note, @leb_size is the logical eraseblock size offered by the UBI device.
 * Volumes of this UBI device may have smaller logical eraseblock size if their
 * alignment is not equivalent to %1.
 *
 * The @max_write_size field describes flash write maximum write unit. For
 * example, NOR flash allows for changing individual bytes, so @min_io_size is
 * %1. However, it does not mean than NOR flash has to write data byte-by-byte.
 * Instead, CFI NOR flashes have a write-buffer of, e.g., 64 bytes, and when
 * writing large chunks of data, they write 64-bytes at a time. Obviously, this
 * improves write throughput.
 *
 * Also, the MTD device may have N interleaved (striped) flash chips
 * underneath, in which case @min_io_size can be physical min. I/O size of
 * single flash chip, while @max_write_size can be N * @min_io_size.
 *
 * The @max_write_size field is always greater or equivalent to @min_io_size.
 * E.g., some NOR flashes may have (@min_io_size = 1, @max_write_size = 64). In
 * contrast, NAND flashes usually have @min_io_size = @max_write_size = NAND
 * page size.
 */
struct ubi_device_info {
	int ubi_num;
	int leb_size;
	int leb_start;
	int min_io_size;
	int max_write_size;
	int ro_mode;
	dev_t cdev;
};

/*
 * Volume notification types.
 * @UBI_VOLUME_ADDED: a volume has been added (an UBI device was attached or a
 *                    volume was created)
 * @UBI_VOLUME_REMOVED: a volume has been removed (an UBI device was detached
 *			or a volume was removed)
 * @UBI_VOLUME_RESIZED: a volume has been re-sized
 * @UBI_VOLUME_RENAMED: a volume has been re-named
 * @UBI_VOLUME_UPDATED: data has been written to a volume
 *
 * These constants define which type of event has happened when a volume
 * notification function is invoked.
 */
enum {
	UBI_VOLUME_ADDED,
	UBI_VOLUME_REMOVED,
	UBI_VOLUME_RESIZED,
	UBI_VOLUME_RENAMED,
	UBI_VOLUME_UPDATED,
};

/*
 * struct ubi_notification - UBI notification description structure.
 * @di: UBI device description object
 * @vi: UBI volume description object
 *
 * UBI notifiers are called with a pointer to an object of this type. The
 * object describes the notification. Namely, it provides a description of the
 * UBI device and UBI volume the notification informs about.
 */
struct ubi_notification {
	struct ubi_device_info di;
	struct ubi_volume_info vi;
};

/* UBI descriptor given to users when they open UBI volumes */
struct ubi_volume_desc;

int ubi_get_device_info(int ubi_num, struct ubi_device_info *di);
void ubi_get_volume_info(struct ubi_volume_desc *desc,
			 struct ubi_volume_info *vi);
struct ubi_volume_desc *ubi_open_volume(int ubi_num, int vol_id, int mode);
struct ubi_volume_desc *ubi_open_volume_nm(int ubi_num, const char *name,
					   int mode);
struct ubi_volume_desc *ubi_open_volume_path(const char *pathname, int mode);

int ubi_register_volume_notifier(struct notifier_block *nb,
				 int ignore_existing);
int ubi_unregister_volume_notifier(struct notifier_block *nb);

void ubi_close_volume(struct ubi_volume_desc *desc);
int ubi_leb_read(struct ubi_volume_desc *desc, int lnum, char *buf, int offset,
		 int len, int check);
int ubi_leb_read_sg(struct ubi_volume_desc *desc, int lnum, struct ubi_sgl *sgl,
		   int offset, int len, int check);
int ubi_leb_write(struct ubi_volume_desc *desc, int lnum, const void *buf,
		  int offset, int len);
int ubi_leb_change(struct ubi_volume_desc *desc, int lnum, const void *buf,
		   int len);
int ubi_leb_erase(struct ubi_volume_desc *desc, int lnum);
int ubi_leb_unmap(struct ubi_volume_desc *desc, int lnum);
int ubi_leb_map(struct ubi_volume_desc *desc, int lnum);
int ubi_is_mapped(struct ubi_volume_desc *desc, int lnum);
int ubi_sync(int ubi_num);
int ubi_flush(int ubi_num, int vol_id, int lnum);

/*
 * This function is the same as the 'ubi_leb_read()' function, but it does not
 * provide the checking capability.
 */
static inline int ubi_read(struct ubi_volume_desc *desc, int lnum, char *buf,
			   int offset, int len)
{
	return ubi_leb_read(desc, lnum, buf, offset, len, 0);
}

/*
 * This function is the same as the 'ubi_leb_read_sg()' function, but it does
 * not provide the checking capability.
 */
static inline int ubi_read_sg(struct ubi_volume_desc *desc, int lnum,
			      struct ubi_sgl *sgl, int offset, int len)
{
	return ubi_leb_read_sg(desc, lnum, sgl, offset, len, 0);
}
#endif /* !__LINUX_UBI_H__ */
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