[GitHub] [incubator-nuttx] XinStellaris commented on a diff in pull request #6829: drivers/mtd:init commit of power-loss resilient cfg

[GitBox <gi...@apache.org>]

XinStellaris commented on code in PR #6829:
URL: https://github.com/apache/incubator-nuttx/pull/6829#discussion_r960159046


##########
drivers/mtd/mtd_config_fs.c:
##########
@@ -0,0 +1,2484 @@
+/****************************************************************************
+ * drivers/mtd/mtd_config_fs.c
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.  The
+ * ASF licenses this file to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance with the
+ * License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+ * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
+ * License for the specific language governing permissions and limitations
+ * under the License.
+ *
+ * NVS: non volatile storage in flash
+ *
+ * Copyright (c) 2018 Laczen
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+#include <sys/types.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <string.h>
+#include <debug.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <sys/poll.h>
+#include <nuttx/crc8.h>
+#include <nuttx/kmalloc.h>
+#include <nuttx/mtd/mtd.h>
+#include <nuttx/mtd/configdata.h>
+
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+
+#define MIN(a, b)                       ((a) > (b) ? (b) : (a))
+
+/* MASKS AND SHIFT FOR ADDRESSES
+ * an address in nvs is an uint32_t where:
+ *   high 2 bytes represent the sector number
+ *   low 2 bytes represent the offset in a sector
+ */
+
+#define ADDR_SECT_MASK                  0xFFFF0000
+#define ADDR_SECT_SHIFT                 16
+#define ADDR_OFFS_MASK                  0x0000FFFF
+
+/* we don't want to store all the read content in stack or heap,
+ * so we make a buffer to do compare or move.
+ */
+
+#define NVS_BUFFER_SIZE                 32
+
+/* if data is written after last ate, and power loss happens,
+ * we need to find a clean offset by skipping dirty data.
+ * This macro defines how many bytes to skip when dirty data
+ * is spotted(may take several skips).
+ * Normally 1 byte is okay, such process only happens when
+ * nvs is started, and it is acceptable to take some time during
+ * starting.
+ */
+
+#define NVS_CORRUPT_DATA_SKIP_STEP      1
+
+#define NVS_LOOKUP_CACHE_NO_ADDR        0xffffffff
+
+/* gc done or close ate has the id of 0xffffffff.
+ * We can tell if the ate is special by looking at its id.
+ */
+
+#define NVS_SPECIAL_ATE_ID              0xffffffff

Review Comment:
   the special value doesn't need to be the same as erase value. Here it is defined as 0xffffffff for simplicity.



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