457ade48b4
Clean some parts of the code and refactor it to avoid multiple nested conditions. Signed-off-by: Riadh Ghaddab <rghaddab@baylibre.com>
99 lines
3.9 KiB
C
99 lines
3.9 KiB
C
/* Copyright (c) 2024 BayLibre SAS
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*
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* SPDX-License-Identifier: Apache-2.0
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*/
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#ifndef __SETTINGS_ZMS_H_
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#define __SETTINGS_ZMS_H_
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#include <zephyr/fs/zms.h>
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#include <zephyr/settings/settings.h>
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#ifdef __cplusplus
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extern "C" {
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#endif
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/* In the ZMS backend, each setting is stored in two ZMS entries:
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* 1. setting's name
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* 2. setting's value
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*
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* The ZMS entry ID for the setting's value is determined implicitly based on
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* the ID of the ZMS entry for the setting's name, once that is found. The
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* difference between name and value ID is constant and equal to
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* ZMS_DATA_ID_OFFSET.
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*
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* Setting's name is hashed into 29 bits minus hash_collisions_bits.
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* The 2 MSB_bits have always the same value 10, the LL_bit for the name's hash is 0
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* and the hash_collisions_bits is configurable through CONFIG_SETTINGS_ZMS_MAX_COLLISIONS_BITS.
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* The resulted 32 bits is the ZMS_ID of the Setting's name.
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* If we detect a collision between ZMS_IDs we increment the value within hash_collision_bits
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* until we find a free ZMS_ID.
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* Separately, we store a linked list using the Setting's name ZMS_ID but setting the lsb to 1.
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*
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* The linked list is used to maintain a relation between all ZMS_IDs. This is necessary to load
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* all settings at initialization.
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* The linked list contains at least a header followed by multiple linked list elements that
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* we can refer to as LL_x (where x is the order of that element in that list).
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* This is a representation of the Linked List that is stored in the storage.
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* LL_header <--> LL_0 <--> LL_1 <--> LL_2.
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* The "next_hash" pointer of each LL element refers to the next element in the linked list.
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* The "previous_hash" pointer is referring the previous element in the linked list.
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*
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* The bit representation of the 32 bits ZMS_ID is the following:
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* --------------------------------------------------------------
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* | MSB_bits | hash (truncated) | hash_collision_bits | LL_bit |
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* --------------------------------------------------------------
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* Where:
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* MSB_bits (2 bits width) : = 10 for Name IDs
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* = 11 for Data IDs
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* hash (29 bits - hash_collision_bits) : truncated hash obtained from sys_hash32
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* hash_collision_bits (configurable width) : used to handle hash collisions
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* LL_bit : = 0 when this is a name's ZMS_ID
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* = 1 when this is the linked list ZMS_ID corresponding to the name
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*
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* if a settings element is deleted it won't be found.
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*/
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#define ZMS_LL_HEAD_HASH_ID 0x80000000
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#define ZMS_DATA_ID_OFFSET 0x40000000
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#define ZMS_HASH_MASK GENMASK(29, CONFIG_SETTINGS_ZMS_MAX_COLLISIONS_BITS + 1)
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#define ZMS_COLLISIONS_MASK GENMASK(CONFIG_SETTINGS_ZMS_MAX_COLLISIONS_BITS, 1)
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#define ZMS_HASH_TOTAL_MASK GENMASK(29, 1)
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#define ZMS_MAX_COLLISIONS (BIT(CONFIG_SETTINGS_ZMS_MAX_COLLISIONS_BITS) - 1)
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/* some useful macros */
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#define ZMS_NAME_ID_FROM_LL_NODE(x) (x & ~BIT(0))
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#define ZMS_LL_NODE_FROM_NAME_ID(x) (x | BIT(0))
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#define ZMS_UPDATE_COLLISION_NUM(x, y) \
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((x & ~ZMS_COLLISIONS_MASK) | ((y << 1) & ZMS_COLLISIONS_MASK))
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#define ZMS_COLLISION_NUM(x) ((x & ZMS_COLLISIONS_MASK) >> 1)
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#define ZMS_NAME_ID_FROM_HASH(x) ((x & ZMS_HASH_TOTAL_MASK) | BIT(31))
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#define ZMS_DATA_ID_FROM_HASH(x) (ZMS_NAME_ID_FROM_HASH(x) + ZMS_DATA_ID_OFFSET)
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#define ZMS_DATA_ID_FROM_NAME(x) (x + ZMS_DATA_ID_OFFSET)
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#define ZMS_DATA_ID_FROM_LL_NODE(x) (ZMS_NAME_ID_FROM_LL_NODE(x) + ZMS_DATA_ID_OFFSET)
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struct settings_hash_linked_list {
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uint32_t previous_hash;
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uint32_t next_hash;
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};
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struct settings_zms {
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struct settings_store cf_store;
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struct zms_fs cf_zms;
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const struct device *flash_dev;
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#if CONFIG_SETTINGS_ZMS_LL_CACHE
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struct settings_hash_linked_list ll_cache[CONFIG_SETTINGS_ZMS_LL_CACHE_SIZE];
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uint32_t ll_cache_next;
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bool ll_has_changed;
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#endif /* CONFIG_SETTINGS_ZMS_LL_CACHE */
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uint32_t last_hash_id;
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uint32_t second_to_last_hash_id;
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uint8_t hash_collision_num;
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};
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#ifdef __cplusplus
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}
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#endif
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#endif /* __SETTINGS_ZMS_H_ */
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