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/* Copyright 2016 The Chromium OS Authors. All rights reserved.
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#ifndef __EC_INCLUDE_NVMEM_VARS_H
#define __EC_INCLUDE_NVMEM_VARS_H
#ifdef __cplusplus
extern "C" {
#endif
/*
* CONFIG_FLASH_NVMEM provides persistent, atomic-update storage in
* flash. The storage is logically divided into one or more "user regions", as
* configured in board.h and board.c
*
* CONFIG_FLASH_NVMEM_VARS stores a set of <KEY, VALUE> tuples in the nvmem
* user region designated by CONFIG_FLASH_NVMEM_VARS_USER_NUM (in board.h)
*
* Tuples are stored and managed using this struct:
*/
struct tuple {
uint8_t key_len; /* 1 - 255 */
uint8_t val_len; /* 1 - 255 */
uint8_t flags; /* RESERVED, will be zeroed */
uint8_t data_[0]; /* Opaque. Don't look here. */
};
/*
* Both KEY and VALUE can be any binary blob between 1 and 255 bytes (flash
* memory is limited, so if you need longer values just use two keys and
* concatenate the blobs). Zero-length KEYs or VALUEs are not allowed.
* Assigning a zero-length VALUE to a KEY just deletes that tuple (if it
* existed).
*
* The expected usage is:
*
* 1. At boot, call initvars() to ensure that the variable storage region is
* valid. If it isn't, this will initialize it to an empty set.
*
* 2. Call getenv() or setenv() as needed. The first call to either will copy
* the storage regsion from flash into a RAM buffer. Any changes made with
* setenv() will affect only that RAM buffer.
*
* 3. Call writevars() to commit the RAM buffer to flash and free it.
*
* CAUTION: The underlying CONFIG_FLASH_NVMEM implementation allows access by
* multiple tasks, provided each task access only one user region. There is no
* support for simultaneous access to the *same* user region by multiple tasks.
* CONFIG_FLASH_NVMEM_VARS stores all variables in one user region, so if
* variable access by multiple tasks is required, the tasks should establish
* their own locks or mutexes to fit their usage. In general that would mean
* aquiring a lock before calling getvar() or setvar(), and releasing it after
* calling writevars().
*/
/*
* Initialize the persistent storage. This checks the user region to ensure
* that all tuples are valid and that there is one additional '\0' at the end.
* If any discrepancies are found, it erases all values. This should return
* EC_SUCCESS unless there is a problem writing to flash.
*/
int initvars(void);
/*
* Look up a key, return a pointer to the tuple. If the key is not found,
* return NULL. WARNING: The returned pointer is only valid until the next call
* to setvar() or writevars(). Use it or lose it.
*/
const struct tuple *getvar(const uint8_t *key, uint8_t key_len);
/* Use these to access the data components of a valid struct tuple pointer */
const uint8_t *tuple_key(const struct tuple *);
const uint8_t *tuple_val(const struct tuple *);
/*
* Save the tuple in the RAM buffer. If val is NULL or val_len is 0, the
* tuple is deleted (if it existed). Returns EC_SUCCESS or error code.
*/
int setvar(const uint8_t *key, uint8_t key_len,
const uint8_t *val, uint8_t val_len);
/*
* Commit any changes made with setvar() to persistent memory, and invalidate
* the RAM buffer. Return EC_SUCCESS or error code on failure.
*/
int writevars(void);
#ifdef __cplusplus
}
#endif
#endif /* __EC_INCLUDE_NVMEM_VARS_H */
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