Revert "[nrf noup] settings: nvs: use dedicated lookup cache hash function"

This reverts commit 98ba1b4.

Signed-off-by: Andrzej Głąbek <[email protected]>

Author: anangl

subsys/fs/nvs/Kconfig

@@ -29,15 +29,6 @@ config NVS_LOOKUP_CACHE_SIZE
 	  Number of entries in Non-volatile Storage lookup cache.
 	  It is recommended that it be a power of 2.
 
-config NVS_LOOKUP_CACHE_FOR_SETTINGS
-	bool "Non-volatile Storage lookup cache optimized for settings"
-	depends on NVS_LOOKUP_CACHE
-	help
-	  Use the lookup cache hash function that results in the least number of
-	  collissions and, in turn, the best NVS performance provided that the NVS
-	  is used as the settings backend only. This option should NOT be enabled
-	  if the NVS is also written to directly, outside the settings layer.
-
 module = NVS
 module-str = nvs
 source "subsys/logging/Kconfig.template.log_config"

subsys/fs/nvs/nvs.c

@@ -13,11 +13,6 @@
 #include <zephyr/sys/crc.h>
 #include "nvs_priv.h"
 
-#ifdef CONFIG_NVS_LOOKUP_CACHE_FOR_SETTINGS
-#include <zephyr/sys/util.h>
-#include <settings/settings_nvs.h>
-#endif
-
 #include <zephyr/logging/log.h>
 LOG_MODULE_REGISTER(fs_nvs, CONFIG_NVS_LOG_LEVEL);
 
@@ -26,45 +21,6 @@ static int nvs_ate_valid(struct nvs_fs *fs, const struct nvs_ate *entry);
 
 #ifdef CONFIG_NVS_LOOKUP_CACHE
 
-#ifdef CONFIG_NVS_LOOKUP_CACHE_FOR_SETTINGS
-
-static inline size_t nvs_lookup_cache_pos(uint16_t id)
-{
-	/*
-	 * 1. The NVS settings backend uses up to (NVS_NAME_ID_OFFSET - 1) NVS IDs to
-	      store keys and equal number of NVS IDs to store values.
-	 * 2. For each key-value pair, the value is stored at NVS ID greater by exactly
-	 *    NVS_NAME_ID_OFFSET than NVS ID that holds the key.
-	 * 3. The backend tries to minimize the range of NVS IDs used to store keys.
-	 *    That is, NVS IDs are allocated sequentially, and freed NVS IDs are reused
-	 *    before allocating new ones.
-	 *
-	 * Therefore, to assure the least number of collisions in the lookup cache,
-	 * the least significant bit of the hash indicates whether the given NVS ID
-	 * represents a key or a value, and remaining bits of the hash are set to
-	 * the ordinal number of the key-value pair. Consequently, the hash function
-	 * provides the following mapping:
-	 *
-	 * 1st settings key   => hash 0
-	 * 1st settings value => hash 1
-	 * 2nd settings key   => hash 2
-	 * 2nd settings value => hash 3
-	 * ...
-	 */
-	BUILD_ASSERT(IS_POWER_OF_TWO(NVS_NAMECNT_ID), "NVS_NAMECNT_ID is not power of 2");
-	BUILD_ASSERT(IS_POWER_OF_TWO(NVS_NAME_ID_OFFSET), "NVS_NAME_ID_OFFSET is not power of 2");
-
-	uint16_t key_value_bit;
-	uint16_t key_value_ord;
-
-	key_value_bit = (id >> LOG2(NVS_NAME_ID_OFFSET)) & 1;
-	key_value_ord = id & (NVS_NAME_ID_OFFSET - 1);
-
-	return ((key_value_ord << 1) | key_value_bit) % CONFIG_NVS_LOOKUP_CACHE_SIZE;
-}
-
-#else /* CONFIG_NVS_LOOKUP_CACHE_FOR_SETTINGS */
-
 static inline size_t nvs_lookup_cache_pos(uint16_t id)
 {
 	uint16_t hash;
@@ -80,8 +36,6 @@ static inline size_t nvs_lookup_cache_pos(uint16_t id)
 	return hash % CONFIG_NVS_LOOKUP_CACHE_SIZE;
 }
 
-#endif /* CONFIG_NVS_LOOKUP_CACHE_FOR_SETTINGS */
-
 static int nvs_lookup_cache_rebuild(struct nvs_fs *fs)
 {
 	int rc;