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971e758dde
The CONFIG_FLASH_NVMEM option implements persistent, reliable storage
regions in flash. This adds CONFIG_FLASH_NVMEM_VARS, which uses one of
those storage regions for free-form variables.
Refer to the comments in include/nvmem_vars.h and common/nvmem_vars.c
for usage and implementation details.
BUG=chrome-os-partner:61107
BRANCH=none
TEST=make runtests
This CL includes a number of new tests, specifically for this feature.
No target boards use this feature yet so there's nothing to test on
actual hardware, but the test/nvmem_vars executable includes console
commands ("get", "set", "print") to try it out.
Change-Id: I8597415dc3b00a1462f5b164eeb5073129030525
Signed-off-by: Bill Richardson <wfrichar@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/414194
Reviewed-by: Randall Spangler <rspangler@chromium.org>
Reviewed-by: Vadim Bendebury <vbendeb@chromium.org>
88 lines
3.3 KiB
C
88 lines
3.3 KiB
C
/* Copyright 2016 The Chromium OS Authors. All rights reserved.
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* Use of this source code is governed by a BSD-style license that can be
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* found in the LICENSE file.
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*/
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#ifndef __EC_INCLUDE_NVMEM_VARS_H
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#define __EC_INCLUDE_NVMEM_VARS_H
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/*
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* CONFIG_FLASH_NVMEM provides persistent, atomic-update storage in
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* flash. The storage is logically divided into one or more "user regions", as
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* configured in board.h and board.c
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*
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* CONFIG_FLASH_NVMEM_VARS stores a set of <KEY, VALUE> tuples in the nvmem
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* user region designated by CONFIG_FLASH_NVMEM_VARS_USER_NUM (in board.h)
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*
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* Tuples are stored and managed using this struct:
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*/
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struct tuple {
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uint8_t key_len; /* 1 - 255 */
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uint8_t val_len; /* 1 - 255 */
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uint8_t flags; /* RESERVED, will be zeroed */
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uint8_t data_[0]; /* Opaque. Don't look here. */
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};
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/*
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* Both KEY and VALUE can be any binary blob between 1 and 255 bytes (flash
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* memory is limited, so if you need longer values just use two keys and
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* concatenate the blobs). Zero-length KEYs or VALUEs are not allowed.
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* Assigning a zero-length VALUE to a KEY just deletes that tuple (if it
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* existed).
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*
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* The expected usage is:
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*
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* 1. At boot, call initvars() to ensure that the variable storage region is
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* valid. If it isn't, this will initialize it to an empty set.
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*
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* 2. Call getenv() or setenv() as needed. The first call to either will copy
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* the storage regsion from flash into a RAM buffer. Any changes made with
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* setenv() will affect only that RAM buffer.
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*
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* 3. Call writevars() to commit the RAM buffer to flash and free it.
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*
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* CAUTION: The underlying CONFIG_FLASH_NVMEM implementation allows access by
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* multiple tasks, provided each task access only one user region. There is no
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* support for simultaneous access to the *same* user region by multiple tasks.
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* CONFIG_FLASH_NVMEM_VARS stores all variables in one user region, so if
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* variable access by multiple tasks is required, the tasks should establish
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* their own locks or mutexes to fit their usage. In general that would mean
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* aquiring a lock before calling getvar() or setvar(), and releasing it after
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* calling writevars().
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*/
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/*
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* Initialize the persistent storage. This checks the user region to ensure
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* that all tuples are valid and that there is one additional '\0' at the end.
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* If any discrepancies are found, it erases all values. This should return
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* EC_SUCCESS unless there is a problem writing to flash.
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*/
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int initvars(void);
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/*
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* Look up a key, return a pointer to the tuple. If the key is not found,
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* return NULL. WARNING: The returned pointer is only valid until the next call
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* to setvar() or writevars(). Use it or lose it.
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*/
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const struct tuple *getvar(const uint8_t *key, uint8_t key_len);
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/* Use these to access the data components of a valid struct tuple pointer */
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const uint8_t *tuple_key(const struct tuple *);
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const uint8_t *tuple_val(const struct tuple *);
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/*
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* Save the tuple in the RAM buffer. If val is NULL or val_len is 0, the
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* tuple is deleted (if it existed). Returns EC_SUCCESS or error code.
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*/
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int setvar(const uint8_t *key, uint8_t key_len,
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const uint8_t *val, uint8_t val_len);
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/*
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* Commit any changes made with setvar() to persistent memory, and invalidate
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* the RAM buffer. Return EC_SUCCESS or error code on failure.
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*/
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int writevars(void);
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#endif /* __EC_INCLUDE_NVMEM_VARS_H */
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