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Lib/dhara/map.h

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+/* Dhara - NAND flash management layer
+ * Copyright (C) 2013 Daniel Beer <dlbeer@gmail.com>
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#ifndef DHARA_MAP_H_
+#define DHARA_MAP_H_
+
+#include "journal.h"
+
+/* The map is a journal indexing format. It maps virtual sectors to
+ * pages of data in flash memory.
+ */
+typedef uint32_t dhara_sector_t;
+
+/* This sector value is reserved */
+#define DHARA_SECTOR_NONE	0xffffffff
+
+struct dhara_map {
+	struct dhara_journal	journal;
+
+	uint8_t			gc_ratio;
+	dhara_sector_t		count;
+};
+
+/* Initialize a map. You need to supply a buffer for page metadata, and
+ * a garbage collection ratio. This is the ratio of garbage collection
+ * operations to real writes when automatic collection is active.
+ *
+ * Smaller values lead to faster and more predictable IO, at the
+ * expense of capacity. You should always initialize the same chip with
+ * the same garbage collection ratio.
+ */
+void dhara_map_init(struct dhara_map *m, const struct dhara_nand *n,
+		    uint8_t *page_buf, uint8_t gc_ratio);
+
+/* Recover stored state, if possible. If there is no valid stored state
+ * on the chip, -1 is returned, and an empty map is initialized.
+ */
+int dhara_map_resume(struct dhara_map *m, dhara_error_t *err);
+
+/* Clear the map (delete all sectors). */
+void dhara_map_clear(struct dhara_map *m);
+
+/* Obtain the maximum capacity of the map. */
+dhara_sector_t dhara_map_capacity(const struct dhara_map *m);
+
+/* Obtain the current number of allocated sectors. */
+static inline dhara_sector_t dhara_map_size(const struct dhara_map *m)
+{
+	return m->count;
+}
+
+/* Find the physical page which holds the current data for this sector.
+ * Returns 0 on success or -1 if an error occurs. If the sector doesn't
+ * exist, the error is E_NOT_FOUND.
+ */
+int dhara_map_find(struct dhara_map *m, dhara_sector_t s,
+		   dhara_page_t *loc, dhara_error_t *err);
+
+/* Read from the given logical sector. If the sector is unmapped, a
+ * blank page (0xff) will be returned.
+ */
+int dhara_map_read(struct dhara_map *m, dhara_sector_t s,
+		   uint8_t *data, dhara_error_t *err);
+
+/* Write data to a logical sector. */
+int dhara_map_write(struct dhara_map *m, dhara_sector_t s,
+		    const uint8_t *data, dhara_error_t *err);
+
+/* Copy any flash page to a logical sector. */
+int dhara_map_copy_page(struct dhara_map *m, dhara_page_t src,
+			dhara_sector_t dst, dhara_error_t *err);
+
+/* Copy one sector to another. If the source sector is unmapped, the
+ * destination sector will be trimmed.
+ */
+int dhara_map_copy_sector(struct dhara_map *m, dhara_sector_t src,
+			  dhara_sector_t dst, dhara_error_t *err);
+
+/* Delete a logical sector. You don't necessarily need to do this, but
+ * it's a useful hint if you no longer require the sector's data to be
+ * kept.
+ *
+ * If order is non-zero, it specifies that all sectors in the
+ * (2**order)-aligned group of s are to be deleted.
+ */
+int dhara_map_trim(struct dhara_map *m, dhara_sector_t s,
+		   dhara_error_t *err);
+
+/* Synchronize the map. Once this returns successfully, all changes to
+ * date are persistent and durable. Conversely, there is no guarantee
+ * that unsynchronized changes will be persistent.
+ */
+int dhara_map_sync(struct dhara_map *m, dhara_error_t *err);
+
+/* Perform one garbage collection step. You can do this whenever you
+ * like, but it's not necessary -- garbage collection happens
+ * automatically and is interleaved with other operations.
+ */
+int dhara_map_gc(struct dhara_map *m, dhara_error_t *err);
+
+#endif