flash_journal.h

00001 /*
00002  * Copyright (c) 2006-2016, ARM Limited, All Rights Reserved
00003  * SPDX-License-Identifier: Apache-2.0
00004  *
00005  * Licensed under the Apache License, Version 2.0 (the "License"); you may
00006  * not use this file except in compliance with the License.
00007  * You may obtain a copy of the License at
00008  *
00009  * http://www.apache.org/licenses/LICENSE-2.0
00010  *
00011  * Unless required by applicable law or agreed to in writing, software
00012  * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
00013  * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
00014  * See the License for the specific language governing permissions and
00015  * limitations under the License.
00016  */
00017 
00018 #ifndef __FLASH_JOURNAL_H__
00019 #define __FLASH_JOURNAL_H__
00020 
00021 #ifdef __cplusplus
00022 extern "C" {
00023 #endif // __cplusplus
00024 
00025 #include "storage_abstraction/Driver_Storage.h"
00026 
00027 /**
00028  * General return codes. All Flash-Journal APIs return an int32_t to allow for
00029  * both error and success status returns. This enumeration contains all
00030  * possible error status values.
00031  */
00032 typedef enum _FlashJournal_Status
00033 {
00034     JOURNAL_STATUS_OK                =   0,
00035     JOURNAL_STATUS_ERROR             =  -1, ///< Unspecified error
00036     JOURNAL_STATUS_BUSY              =  -2, ///< Underlying storage is currently unavailable
00037     JOURNAL_STATUS_TIMEOUT           =  -3, ///< Timeout occurred
00038     JOURNAL_STATUS_UNSUPPORTED       =  -4, ///< Operation not supported
00039     JOURNAL_STATUS_PARAMETER         =  -5, ///< Parameter error
00040     JOURNAL_STATUS_BOUNDED_CAPACITY  =  -6, ///< Attempt to write larger than available capacity
00041     JOURNAL_STATUS_STORAGE_API_ERROR =  -7, ///< Failure from some Storage API
00042     JOURNAL_STATUS_STORAGE_IO_ERROR  =  -8, ///< Failure from underlying storage during an IO operation.
00043     JOURNAL_STATUS_NOT_INITIALIZED   =  -9, ///< journal not initialized
00044     JOURNAL_STATUS_EMPTY             = -10, ///< There is no further data to read
00045     JOURNAL_STATUS_SMALL_LOG_REQUEST = -11, ///< log request is smaller than the program_unit of the underlying MTD block.
00046     JOURNAL_STATUS_NOT_FORMATTED     = -12, ///< need to call xxx_format() before using the journal.
00047     JOURNAL_STATUS_METADATA_ERROR    = -13, ///< sanity checks for the journal metadata failed.
00048     JOURNAL_STATUS_STORAGE_RUNTIME_OR_INTEGRITY_FAILURE = -14, ///< validation or run-time errors arising from the badkend media.
00049 } FlashJournal_Status_t;
00050 
00051 /**
00052  * Command opcodes for flash. Completion callbacks use these codes to refer to
00053  * completing commands. Refer to \ref ARM_Flash_Callback_t.
00054  */
00055 typedef enum _FlashJournal_OpCode {
00056     FLASH_JOURNAL_OPCODE_FORMAT,
00057     FLASH_JOURNAL_OPCODE_INITIALIZE,
00058     FLASH_JOURNAL_OPCODE_GET_INFO,
00059     FLASH_JOURNAL_OPCODE_READ_BLOB,
00060     FLASH_JOURNAL_OPCODE_LOG_BLOB,
00061     FLASH_JOURNAL_OPCODE_COMMIT,
00062     FLASH_JOURNAL_OPCODE_RESET,
00063 } FlashJournal_OpCode_t;
00064 
00065 /**
00066  * @brief Flash Journal information. This contains journal-metadata, and is the
00067  *     return value from calling GetInfo() on the journal driver.
00068  */
00069 typedef struct _FlashJournal_Info {
00070     uint64_t capacity;             ///< Maximum capacity (in octets) of the flash journal--i.e. the largest 'blob' which can be contained as payload.
00071     uint64_t sizeofJournaledBlob;  ///< size (in octets) of the most recently logged blob.
00072     uint32_t program_unit;         ///< Minimum programming size (in units of octets) for
00073                                    ///<   the current storage block--the one which will be used
00074                                    ///<   for the next log() operation. This value may change as we
00075                                    ///<   cycle through the blocks of the underlying MTD.
00076                                    ///<   Callers of FlashJournal_log() should refer to this field
00077                                    ///<   upon receiving the error JOURNAL_STATUS_SMALL_LOG_REQUEST
00078                                    ///<   (of when the actual amount of data logged is smaller than
00079                                    ///<   the requested amount).
00080 } FlashJournal_Info_t;
00081 
00082 
00083 static const uint32_t FLASH_JOURNAL_HEADER_MAGIC   = 0xA00AEE1DUL;
00084 static const uint32_t FLASH_JOURNAL_HEADER_VERSION = 1;
00085 
00086 /**
00087  * Meta-data placed at the head of a Journal. The actual header would be an
00088  * extension of this generic header, and would depend on the implementation
00089  * strategy. Initialization algorithms can expect to find this generic header at
00090  * the start of every Journal.
00091  */
00092 typedef struct _FlashJournalHeader {
00093     uint32_t magic;         /** Journal-header specific magic code */
00094     uint32_t version;       /** Revision number for this generic journal header. */
00095     uint64_t totalSize;     /** Total space (in bytes) occupied by the journal, including the header.
00096                              *    Both 'mtdOffset' and 'mtdOffset + totalSize' should
00097                              *    lie on erase boundaries. */
00098     uint32_t sizeofHeader;  /** The size of the journal header; this is expected to be larger than this generic header. */
00099     uint32_t journalOffset; /** Offset from the start of the journal header to the actual logged journal. */
00100     uint32_t checksum;      /** CRC32 over the entire flash-journal-header, including the implementation
00101                              *    specific extension (i.e. over 'sizeofHeader' bytes). The value of the
00102                              *    field is taken to be 0 for the purpose of computing the checksum. */
00103 } FlashJournalHeader_t;
00104 
00105 /**
00106  * This is the type of the command completion callback handler for the
00107  * asynchronous flash-journal APIs: initialize(), read(), log(), commit() and
00108  * reset() (which is nearly all APIs).
00109  *
00110  * @param status
00111  *          A code to indicate the status of the completed operation. For data
00112  *          transfer operations, the status field is overloaded in case of
00113  *          success to return the amount of data successfully transferred; this
00114  *          can be done safely because error codes are negative values.
00115  *
00116  * @param cmd_code
00117  *          The command op-code of type FlashJournal_OpCode_t. This value isn't
00118  *          essential for the callback, but it is expected that this information
00119  *          could be a quick and useful filter.
00120  */
00121 typedef void (*FlashJournal_Callback_t)(int32_t status, FlashJournal_OpCode_t cmd_code);
00122 
00123 /* forward declarations. */
00124 struct FlashJournal_t;
00125 
00126 /**
00127  * @ref FlashJournal_t is an abstraction implemented by a table of generic
00128  * operations (i.e. strategy) together with an opaque, strategy-specific
00129  * data. Taken together, the FlashJournal_t is an opaque handle containing
00130  * such top-level metadata.
00131  *
00132  * Algorithms depending on the FlashJournal can be generic (i.e. independent of
00133  * the strategy) in their use of the Flash-Journal APIs. For the sake of being
00134  * able to allocate a FlashJournal_t for use in such generic algorithms, the
00135  * FlashJournal_t contains a MAX_SIZE to accommodate the largest of the
00136  * strategy-specific metadata. The value of this MAX_SIZE may need to be
00137  * increased if some future journal-strategy needs more metadata.
00138  */
00139 #define FLASH_JOURNAL_HANDLE_MAX_SIZE 160
00140 
00141 /**
00142  * This is the set of operations offered by the flash-journal abstraction. A set
00143  * of implementations for these operations defines a logging strategy.
00144  */
00145 
00146 typedef struct FlashJournal_Ops_t {
00147     /**
00148      * \brief Initialize the flash journal. Refer to @ref FlashJournal_initialize.
00149      */
00150     int32_t               (*initialize)(struct FlashJournal_t           *journal,
00151                                         ARM_DRIVER_STORAGE       *mtd,
00152                                         const struct FlashJournal_Ops_t *ops,
00153                                         FlashJournal_Callback_t   callback);
00154 
00155     /**
00156      * \brief fetch journal metadata. Refer to @ref FlashJournal_getInfo.
00157      */
00158     FlashJournal_Status_t (*getInfo)   (struct FlashJournal_t *journal, FlashJournal_Info_t *info);
00159 
00160     /**
00161      * @brief Read from the most recently logged blob. Refer to @ref FlashJournal_read.
00162      */
00163     int32_t               (*read)      (struct FlashJournal_t *journal, void *buffer, size_t size);
00164 
00165     /**
00166      * @brief Read from the most recently logged blob from a particular offset. Refer to @ref FlashJournal_readFrom.
00167      */
00168     int32_t               (*readFrom)  (struct FlashJournal_t *journal, size_t offset, void *buffer, size_t size);
00169 
00170     /**
00171      * @brief Start logging a new blob or append to the one currently being logged. Refer to @ref FlashJournal_log.
00172      */
00173     int32_t               (*log)       (struct FlashJournal_t *journal, const void *blob, size_t size);
00174 
00175     /**
00176      * @brief commit a blob accumulated through a non-empty sequence of
00177      *     previously successful log() operations. Refer to @ref FlashJournal_commit.
00178      */
00179     int32_t               (*commit)    (struct FlashJournal_t *journal);
00180 
00181     /**
00182      * @brief Reset the journal. This has the effect of erasing all valid blobs.
00183      *     Refer to @ref FlashJournal_reset.
00184      */
00185     int32_t               (*reset)     (struct FlashJournal_t *journal);
00186 } FlashJournal_Ops_t;
00187 
00188 /**
00189  * @brief An opaque handle constituting the Flash Journal.
00190  *
00191  * @details This structure is intentionally opaque to avoid exposing data
00192  *     internal to an implementation strategy; this prevents accesses through any
00193  *     means other than through the defined API.
00194  *
00195  * Having a known size for the handle allows the caller to remain malloc-free.
00196  *
00197  * @note: There should be static asserts in the code to verify our assumption
00198  * that the real FlashJournal handle fits within FLASH_JOURNAL_HANDLE_MAX_SIZE
00199  * bytes.
00200  *
00201  * @note: there is a risk of overallocation in case an implementation doesn't
00202  * need FLASH_JOURNAL_HANDLE_MAX_SIZE bytes, but the impact should be small.
00203  */
00204 typedef struct FlashJournal_t {
00205     FlashJournal_Ops_t       ops;
00206 
00207     union {
00208         ARM_DRIVER_STORAGE  *mtd;
00209         FlashJournal_Info_t  info;
00210         void                *pointer;
00211         uint8_t              octet;
00212         uint32_t             data[FLASH_JOURNAL_HANDLE_MAX_SIZE / sizeof(uint32_t)];
00213     } opaque;
00214 } FlashJournal_t;
00215 
00216 /**
00217  * @brief Initialize a flash journal.
00218  *
00219  * This is a front-end for @ref FlashJournal_Ops_t::initialize() of the
00220  * underlying strategy.
00221  *
00222  * This function must be called *before* the middle-ware component starts
00223  * using a journal. As a part of bringing the journal to a ready state, it
00224  * also discovers the most recently logged blob.
00225  *
00226  * Initialize() receives a callback handler to be invoked upon completion of
00227  * asynchronous operations.
00228  *
00229  * @param [out] journal
00230  *                A caller-supplied buffer large enough to hold an
00231  *                initialized journal. The internals of the actual journal
00232  *                are opaque to the caller and depend on the logging
00233  *                strategy (as defined by the parameter 'ops'). This memory
00234  *                should be at least as large as 'FLASH_JOURNAL_HANDLE_MAX_SIZE'.
00235  *                Upon successful return, the journal is setup in an
00236  *                initialized state.
00237  *
00238  * @param  [in] mtd
00239  *                The underlying Storage_Driver targeted by the journal. MTD
00240  *                stands for Memory-Technology-Device.
00241  *
00242  * @param  [in] ops
00243  *                This is the set of operations which define the logging strategy.
00244  *
00245  * @param  [in] callback
00246  *                Caller-defined callback to be invoked upon command completion of
00247  *                initialization; and also for all future invocations of
00248  *                asynchronous APIs. Use a NULL pointer when no
00249  *                callback signals are required.
00250  *
00251  * @note: this is an asynchronous operation, but it can finish
00252  * synchronously if the underlying MTD supports that.
00253  *
00254  * @return
00255  *   The function executes in the following ways:
00256  *   - When the operation is asynchronous, the function only starts the
00257  *     initialization and control returns to the caller with an
00258  *     JOURNAL_STATUS_OK before the actual completion of the operation (or
00259  *     with an appropriate error code in case of failure). When the
00260  *     operation is completed the command callback is invoked with
00261  *     1 passed in as the 'status' parameter of the
00262  *     callback. In case of errors, the completion callback is invoked with
00263  *     an error status.
00264  *   - When the operation is executed by the journal in a blocking (i.e.
00265  *     synchronous) manner, control returns to the caller only upon the actual
00266  *     completion of the operation or the discovery of a failure condition. In
00267  *     this case, the function returns 1 to signal successful synchronous
00268  *     completion or an appropriate error code, and no further
00269  *     invocation of the completion callback should be expected at a later time.
00270  *
00271  * @note The user must call an appropriate xxx_format() to format underlying
00272  *     storage before initializing it for use. If Initialize() is called on
00273  *     unformatted storage, an error value of JOURNAL_STATUS_NOT_FORMATTED will be
00274  *     returned.
00275  *
00276  * Here's a code snippet to suggest how this API might be used by callers:
00277  * \code
00278  *     ASSERT(JOURNAL_STATUS_OK == 0); // this is a precondition; it doesn't need to be put in code
00279  *     int32_t returnValue = FlashJournal_initialize(&journal, MTD, &STRATEGY_SEQUENTIAL, callbackHandler);
00280  *     if (returnValue < JOURNAL_STATUS_OK) {
00281  *         // handle error
00282  *     } else if (returnValue == JOURNAL_STATUS_OK) {
00283  *         ASSERT(MTD->GetCapabilities().asynchronous_ops == 1);
00284  *         // handle early return from asynchronous execution
00285  *     } else {
00286  *         ASSERT(returnValue == 1);
00287  *         // handle synchronous completion
00288  *     }
00289  * \endcode
00290  */
00291 static inline int32_t FlashJournal_initialize(FlashJournal_t           *journal,
00292                                               ARM_DRIVER_STORAGE       *mtd,
00293                                               const FlashJournal_Ops_t *ops,
00294                                               FlashJournal_Callback_t   callback)
00295 {
00296     return ops->initialize(journal, mtd, ops, callback);
00297 }
00298 
00299 /**
00300  * @brief Fetch journal metadata. A front-end for @ref FlashJournal_Ops_t::getInfo().
00301  *
00302  * @param [in] journal
00303  *                A previously initialized journal.
00304  *
00305  * @param [out] info
00306  *                A caller-supplied buffer capable of being filled in with an
00307  *                FlashJournal_Info_t.
00308  *
00309  * @return JOURNAL_STATUS_OK if a FlashJournal_Info_t structure containing
00310  *         top level metadata about the journal is filled into the supplied
00311  *         buffer, else an appropriate error value.
00312  *
00313  * @note It is the caller's responsibility to ensure that the buffer passed in
00314  *         is able to be initialized with a FlashJournal_Info_t.
00315  *
00316  * @note getInfo()s can still be called during a sequence of
00317  *     log()s.
00318  *
00319  * @note This API returns synchronously--it does not result in an invocation
00320  *     of a completion callback.
00321  *
00322  * Here's a code snippet to suggest how this API might be used by callers:
00323  * \code
00324  *     ASSERT(JOURNAL_STATUS_OK == 0); // this is a precondition; it doesn't need to be put in code
00325  *     FlashJournal_Info_t info;
00326  *     int32_t returnValue = FlashJournal_getInfo(&journal, &info);
00327  *     if (returnValue < JOURNAL_STATUS_OK) {
00328  *         // handle error
00329  *     } else {
00330  *         ASSERT(returnValue == JOURNAL_STATUS_OK);
00331  *         // work with the 'info'.
00332  *     }
00333  * \endcode
00334  */
00335 static inline FlashJournal_Status_t FlashJournal_getInfo(FlashJournal_t *journal, FlashJournal_Info_t *info)
00336 {
00337     return journal->ops.getInfo(journal, info);
00338 }
00339 
00340 /**
00341  * @brief Read from the most recently logged blob. A front-end for @ref
00342  * FlashJournal_Ops_t::read().
00343  *
00344  * @details Read off a chunk of the logged blob sequentially. The blob may
00345  *     be larger than the size of the read (or even of available SRAM), so
00346  *     multiple calls to read() could be necessary before the entire blob is
00347  *     read off. The journal maintains a read-pointer internally to allow
00348  *     reads to continue where the previous one left off.
00349  *
00350  * @note: Once the entire blob is read, the final read() returns the error
00351  *     JOURNAL_STATUS_EMPTY (or passes that value as the status of a
00352  *     completion callback) and resets the read-pointer to allow re-reading
00353  *     the blob from the start.
00354  *
00355  * @param  [in] journal
00356  *                A previously initialized journal.
00357  *
00358  * @param [out] buffer
00359  *                The destination of the read operation. The memory is owned
00360  *                by the caller and should remain valid for the lifetime
00361  *                of this operation.
00362  *
00363  * @param  [in] size
00364  *                The maximum amount of data which can be read in this
00365  *                operation. The memory pointed to by 'buffer' should be as
00366  *                large as this amount.
00367  *
00368  * @return
00369  *    The function executes in the following ways:
00370  *   - When the operation is asynchronous--i.e. when the underlying MTD's
00371  *     ARM_STOR_CAPABILITIES::asynchronous_ops is set to 1--and the operation
00372  *     executed by the journal in a non-blocking (i.e. asynchronous) manner,
00373  *     control returns to the caller with JOURNAL_STATUS_OK before the actual
00374  *     completion of the operation (or with an appropriate error code in case of
00375  *     failure). When the operation completes, the command callback is
00376  *     invoked with the number of successfully transferred bytes passed in as
00377  *     the 'status' parameter of the callback. If any error is encountered
00378  *     after the launch of an asynchronous operation, the completion callback
00379  *     is invoked with an error status.
00380  *   - When the operation is executed by the journal in a blocking (i.e.
00381  *     synchronous) manner, control returns to the caller only upon the
00382  *     actual completion of the operation, or the discovery of a failure
00383  *     condition. In synchronous mode, the function returns the number
00384  *     of data items read or an appropriate error code.
00385  *
00386  * @note If the underlying MTD's ARM_STORAGE_CAPABILITIES::asynchronous_ops
00387  *     is set then this operation may execute asynchronously. In the case of
00388  *     asynchronous operation, the invocation returns early (with
00389  *     JOURNAL_STATUS_OK) and results in a completion callback later.
00390  *
00391  * @note If the underlying MTD's ARM_STORAGE_CAPABILITIES::asynchronous_ops
00392  *     is set, the journal is not required to operate asynchronously. A Read
00393  *     operation can be finished synchronously in spite of
00394  *     ARM_STORAGE_CAPABILITIES::asynchronous_ops being set, returning the
00395  *     number of data items read to indicate successful completion, or an
00396  *     appropriate error code. In this case no further invocation of a
00397  *     completion callback should be expected at a later time.
00398  *
00399  * Here's a code snippet to suggest how this API might be used by callers:
00400  * \code
00401  *     ASSERT(JOURNAL_STATUS_OK == 0); // this is a precondition; it doesn't need to be put in code
00402  *     int32_t returnValue = FlashJournal_read(&journal, buffer, size);
00403  *     if (returnValue < JOURNAL_STATUS_OK) {
00404  *         // handle error
00405  *     } else if (returnValue == JOURNAL_STATUS_OK) {
00406  *         ASSERT(MTD->GetCapabilities().asynchronous_ops == 1);
00407  *         // handle early return from asynchronous execution
00408  *     } else {
00409  *         ASSERT(returnValue == size);
00410  *         // handle synchronous completion
00411  *     }
00412  * \endcode
00413  */
00414 static inline int32_t FlashJournal_read(FlashJournal_t *journal, void *blob, size_t n)
00415 {
00416     return journal->ops.read(journal, blob, n);
00417 }
00418 
00419 /**
00420  * @brief Read from the most recently logged blob at a given offset. A front-end
00421  *     for @ref FlashJournal_Ops_t::readFrom().
00422  *
00423  * @details Read off a chunk of the logged blob from a given offset. The journal
00424  *     maintains a read-pointer internally to allow reads to continue where the
00425  *     previous one left off. This call effectively sets the read-counter before
00426  *     fetching data. Subsequent reads continue sequentially from where the
00427  *     readFrom() left off.
00428  *
00429  * @note: If the given offset stands at (or is beyond) the end of the previously
00430  *     logged blob, readFrom() returns the error JOURNAL_STATUS_EMPTY (or passes
00431  *     that value as the status of a completion callback) and resets the read-
00432  *     pointer to allow re-reading the blob from the start.
00433  *
00434  * @param  [in] journal
00435  *                A previously initialized journal.
00436  *
00437  * @param  [in] offset
00438  *                The logical offset (within the blob) at which to read data from.
00439  *
00440  * @param [out] buffer
00441  *                The destination of the read operation. The memory is owned
00442  *                by the caller and should remain valid for the lifetime
00443  *                of this operation.
00444  *
00445  * @param  [in] size
00446  *                The maximum amount of data which can be read in this
00447  *                operation. The memory pointed to by 'buffer' should be as
00448  *                large as this amount.
00449  *
00450  * @return
00451  *    The function executes in the following ways:
00452  *   - When the operation is asynchronous--i.e. when the underlying MTD's
00453  *     ARM_STOR_CAPABILITIES::asynchronous_ops is set to 1--and the operation
00454  *     executed by the journal in a non-blocking (i.e. asynchronous) manner,
00455  *     control returns to the caller with JOURNAL_STATUS_OK before the actual
00456  *     completion of the operation (or with an appropriate error code in case of
00457  *     failure). When the operation completes, the command callback is
00458  *     invoked with the number of successfully transferred bytes passed in as
00459  *     the 'status' parameter of the callback. If any error is encountered
00460  *     after the launch of an asynchronous operation, the completion callback
00461  *     is invoked with an error status.
00462  *   - When the operation is executed by the journal in a blocking (i.e.
00463  *     synchronous) manner, control returns to the caller only upon the
00464  *     actual completion of the operation, or the discovery of a failure
00465  *     condition. In synchronous mode, the function returns the number
00466  *     of data items read or an appropriate error code.
00467  *
00468  * @note If the underlying MTD's ARM_STORAGE_CAPABILITIES::asynchronous_ops
00469  *     is set then this operation may execute asynchronously. In the case of
00470  *     asynchronous operation, the invocation returns early (with
00471  *     JOURNAL_STATUS_OK) and results in a completion callback later.
00472  *
00473  * @note If the underlying MTD's ARM_STORAGE_CAPABILITIES::asynchronous_ops
00474  *     is set, the journal is not required to operate asynchronously. A Read
00475  *     operation can be finished synchronously in spite of
00476  *     ARM_STORAGE_CAPABILITIES::asynchronous_ops being set, returning the
00477  *     number of data items read to indicate successful completion, or an
00478  *     appropriate error code. In this case no further invocation of a
00479  *     completion callback should be expected at a later time.
00480  *
00481  * Here's a code snippet to suggest how this API might be used by callers:
00482  * \code
00483  *     ASSERT(JOURNAL_STATUS_OK == 0); // this is a precondition; it doesn't need to be put in code
00484  *     int32_t returnValue = FlashJournal_readFrom(&journal, offset, buffer, size);
00485  *     if (returnValue < JOURNAL_STATUS_OK) {
00486  *         // handle error
00487  *     } else if (returnValue == JOURNAL_STATUS_OK) {
00488  *         ASSERT(MTD->GetCapabilities().asynchronous_ops == 1);
00489  *         // handle early return from asynchronous execution
00490  *     } else {
00491  *         ASSERT(returnValue == size);
00492  *         // handle synchronous completion
00493  *     }
00494  * \endcode
00495  */
00496 static inline int32_t FlashJournal_readFrom(struct FlashJournal_t *journal, size_t offset, void *blob, size_t n)
00497 {
00498     return journal->ops.readFrom(journal, offset, blob, n);
00499 }
00500 
00501 /**
00502  * @brief Start logging a new blob or append to the one currently being logged.
00503  * A front-end for @ref FlashJournal_Ops_t::log().
00504  *
00505  * @details Extend (or start off) the currently logged blob sequentially.
00506  *     There could be several calls to log() before the entire blob is
00507  *     accumulated. A sequence of one or more log() must be terminated by a
00508  *     commit() before the state of the blob is sealed and made persistent.
00509  *     The journal maintains a log-pointer internally to allow
00510  *     log()s to continue where the previous one left off.
00511  *
00512  * @param [in] journal
00513  *               A previously initialized journal.
00514  *
00515  * @param [in] blob
00516  *               The source of the log operation. The memory is owned
00517  *               by the caller and should remain valid for the lifetime
00518  *               of this operation.
00519  *
00520  * @param [in] size
00521  *               The amount of data being logged in this operation. The
00522  *               buffer pointed to by 'blob' should be as large as this
00523  *               amount.
00524  *
00525  * @return [please be sure to read notes (below) regarding other return values]
00526  *   The function executes in the following ways:
00527  *   - When the operation is asynchronous--i.e. when the underlying MTD's
00528  *     ARM_STOR_CAPABILITIES::asynchronous_ops is set to 1--and the operation
00529  *     executed by the journal in a non-blocking (i.e. asynchronous) manner,
00530  *     control returns to the caller with JOURNAL_STATUS_OK before the actual
00531  *     completion of the operation (or with an appropriate error code in case of
00532  *     failure). When the operation completes, the command callback is
00533  *     invoked with the number of successfully transferred bytes passed in as
00534  *     the 'status' parameter of the callback. If any error is encountered
00535  *     after the launch of an asynchronous operation, the completion callback
00536  *     is invoked with an error status.
00537  *   - When the operation is executed by the journal in a blocking (i.e.
00538  *     synchronous) manner, control returns to the caller only upon the actual
00539  *     completion of the operation, or the discovery of a failure condition. In
00540  *     synchronous mode, the function returns the number of data items
00541  *     logged, or an appropriate error code.
00542  *
00543  * @note If the underlying MTD's ARM_STORAGE_CAPABILITIES::asynchronous_ops
00544  *     is set then this operation may execute asynchronously. In the case of
00545  *     asynchronous operation, the invocation returns early (with
00546  *     JOURNAL_STATUS_OK) and results in a completion callback later.
00547  *
00548  * @note If the underlying MTD's ARM_STORAGE_CAPABILITIES::asynchronous_ops
00549  *     is set, the journal is not required to operate asynchronously. A log
00550  *     operation can be finished synchronously in spite of
00551  *     ARM_STORAGE_CAPABILITIES::asynchronous_ops being set, returning the
00552  *     number of data items logged to indicate successful completion, or an
00553  *     appropriate error code. In this case no further invocation of a
00554  *     completion callback should be expected at a later time.
00555  *
00556  * @note If a log operation will exceed available capacity, it fails with the
00557  *     error JOURNAL_STATUS_BOUNDED_CAPACITY.
00558  *
00559  * @note The actual size of data transfer (as reported by the status
00560  *     parameter of the callback or the return value from log() in case of
00561  *     synchronous operation) may be smaller than the amount requested. This
00562  *     could be due to the 'program_unit' of the underlying storage block--
00563  *     i.e. the minimum programmable size. Refer to @ref
00564  *     FlashJournal_Info_t::program_unit. It is the caller's responsibility
00565  *     for resubmitting this left-over data in a subsequent call to log.
00566  *     When logging an arbitrary amount of data, the last of a sequence of
00567  *     logs may need to be padded in order to align with the
00568  *     programming unit.
00569  *
00570  * @note If the total size requested to be logged is smaller
00571  *     than the MTD's program_unit, log() fails with an error value of
00572  *     JOURNAL_STATUS_SMALL_LOG_REQUEST.
00573  *
00574  * @note the data being logged isn't made persistent (or available for read-
00575  *     backs) until a commit. A sequence of log() operations is expected to end
00576  *     in a commit(). A new sequence of log()s should be initiated by the caller
00577  *     only after a commit() has completed. If a sequence of logs() is followed
00578  *     by an operation other than a commit, that operation will very likely
00579  *     return an error code. getInfo()s can still be called during a sequence of
00580  *     log()s.
00581  *
00582  * Here's a code snippet to suggest how this API might be used by callers:
00583  * \code
00584  *     ASSERT(JOURNAL_STATUS_OK == 0); // this is a precondition; it doesn't need to be put in code
00585  *     int32_t returnValue = FlashJournal_log(&journal, buffer, size);
00586  *     if (returnValue < JOURNAL_STATUS_OK) {
00587  *         // handle error
00588  *     } else if (returnValue == JOURNAL_STATUS_OK) {
00589  *         ASSERT(MTD->GetCapabilities().asynchronous_ops == 1);
00590  *         // handle early return from asynchronous execution
00591  *     } else {
00592  *         ASSERT(returnValue <= size);
00593  *         // handle synchronous completion
00594  *
00595  *         if (returnValue < size) {
00596  *     #if DEBUG
00597  *             FlashJournal_Info_t info;
00598  *             int32_t rc = FlashJournal_getInfo(&journal, &info);
00599  *             ASSERT(rc == JOURNAL_STATUS_OK);
00600  *             ASSERT(returnValue == (size - (size % info.program_unit)));
00601  *     #endif
00602  *             // move the last (size - returnValue) bytes of the buffer to the
00603  *             // beginning of the buffer to be used for the successive request.
00604  *         }
00605  *     }
00606  * \endcode
00607  */
00608 static inline int32_t FlashJournal_log(FlashJournal_t *journal, const void *blob, size_t n)
00609 {
00610     return journal->ops.log(journal, blob, n);
00611 }
00612 
00613 /**
00614  * @brief Commit a blob accumulated through a (possibly empty) sequence of previously
00615  *     successful log() operations. A front-end for @ref FlashJournal_Ops_t::commit().
00616  *
00617  * @param  [in] journal
00618  *                A previously initialized journal.
00619  *
00620  * @return
00621  *   The function executes in the following ways:
00622  *   - When the operation is asynchronous--i.e. when the underlying MTD's
00623  *     ARM_STOR_CAPABILITIES::asynchronous_ops is set to 1--and the operation
00624  *     executed by the journal in a non-blocking (i.e. asynchronous) manner,
00625  *     control returns to the caller with JOURNAL_STATUS_OK before the actual
00626  *     completion of the operation (or with an appropriate error code in case of
00627  *     failure). When the operation completes, the command callback is invoked
00628  *     with 1 passed in as the 'status' parameter of the callback to indicate
00629  *     success. If any error is encountered after the launch of an asynchronous
00630  *     operation, the completion callback is invoked with an error status.
00631  *   - When the operation is executed by the journal in a blocking (i.e.
00632  *     synchronous) manner, control returns to the caller only upon the actual
00633  *     completion of the operation, or the discovery of a failure condition. In
00634  *     synchronous mode, the function returns 1 to indicate success, or an
00635  *     appropriate error code.
00636  *
00637  * @note If the underlying MTD's ARM_STORAGE_CAPABILITIES::asynchronous_ops
00638  *     is set then this operation may execute asynchronously. In the case of
00639  *     asynchronous operation, the invocation returns early (with
00640  *     JOURNAL_STATUS_OK) and results in a completion callback later.
00641  *
00642  * @note If the underlying MTD's ARM_STORAGE_CAPABILITIES::asynchronous_ops
00643  *     is set, the journal is not required to operate asynchronously. A
00644  *     commit operation can be finished synchronously in spite of
00645  *     ARM_STORAGE_CAPABILITIES::asynchronous_ops being set, returning the
00646  *     total size of the committed blob to indicate successful completion,
00647  *     or an appropriate error code. In this case no further invocation of a
00648  *     completion callback should be expected at a later time.
00649  *
00650  * Here's a code snippet to suggest how this API might be used by callers:
00651  * \code
00652  *     ASSERT(JOURNAL_STATUS_OK == 0); // this is a precondition; it doesn't need to be put in code
00653  *     int32_t returnValue = FlashJournal_commit(&journal);
00654  *     if (returnValue < JOURNAL_STATUS_OK) {
00655  *         // handle error
00656  *     } else if (returnValue == JOURNAL_STATUS_OK) {
00657  *         ASSERT(MTD->GetCapabilities().asynchronous_ops == 1);
00658  *         // handle early return from asynchronous execution
00659  *     } else {
00660  *         // handle synchronous completion
00661  *         ASSERT(returnValue == 1);
00662  *         ...
00663  *     }
00664  * \endcode
00665  *
00666  * @note A sequence of log() operations is expected to end in a commit(). A new
00667  *     sequence of log()s should be initiated by the caller only after a
00668  *     commit() has completed. If a sequence of logs() is followed
00669  *     by an operation other than a commit, that operation will very likely
00670  *     return an error code.
00671  */
00672 static inline int32_t FlashJournal_commit(FlashJournal_t *journal)
00673 {
00674     return journal->ops.commit(journal);
00675 }
00676 
00677 /**
00678  * @brief Reset the journal. This has the effect of erasing all valid blobs. A
00679  *     front-end for @ref FlashJournal_Ops_t::reset().
00680  *
00681  * @param [in] journal
00682  *               A previously initialized journal.
00683  *
00684  * @return
00685  *   The function executes in the following ways:
00686  *   - When the operation is asynchronous--i.e. when the underlying MTD's
00687  *     ARM_STOR_CAPABILITIES::asynchronous_ops is set to 1--and the
00688  *     operation executed by the journal in a non-blocking (i.e.
00689  *     asynchronous) manner, control returns to the caller with
00690  *     JOURNAL_STATUS_OK before the actual completion of the operation (or
00691  *     with an appropriate error code in case of failure). When the
00692  *     operation completes, the command callback is invoked with
00693  *     JOURNAL_STATUS_OK passed in as the 'status' parameter of the
00694  *     callback. If any error is encountered after the launch of an
00695  *     asynchronous operation, the completion callback is invoked with an
00696  *     error status.
00697  *   - When the operation is executed by the journal in a blocking (i.e.
00698  *     synchronous) manner, control returns to the caller only upon the
00699  *     actual completion of the operation, or the discovery of a failure
00700  *     condition. In synchronous mode, the function returns 1 to signal
00701  *     successful completion, or an appropriate error code.
00702  *
00703  * @note If the underlying MTD's ARM_STORAGE_CAPABILITIES::asynchronous_ops
00704  *     is set then this operation may execute asynchronously. In the case of
00705  *     asynchronous operation, the invocation returns early (with
00706  *     JOURNAL_STATUS_OK) and results in a completion callback later.
00707  *
00708  * @note If the underlying MTD's ARM_STORAGE_CAPABILITIES::asynchronous_ops
00709  *     is set, the journal is not required to operate asynchronously. A
00710  *     reset operation can be finished synchronously in spite of
00711  *     ARM_STORAGE_CAPABILITIES::asynchronous_ops being set, returning 1 to
00712  *     indicate successful completion, or an appropriate error code. In this
00713  *     case no further invocation of a completion callback should be
00714  *     expected at a later time.
00715  *
00716  * Here's a code snippet to suggest how this API might be used by callers:
00717  * \code
00718  *     ASSERT(JOURNAL_STATUS_OK == 0); // this is a precondition; it doesn't need to be put in code
00719  *     int32_t returnValue = FlashJournal_reset(&journal);
00720  *     if (returnValue < JOURNAL_STATUS_OK) {
00721  *         // handle error
00722  *     } else if (returnValue == JOURNAL_STATUS_OK) {
00723  *         ASSERT(MTD->GetCapabilities().asynchronous_ops == 1);
00724  *         // handle early return from asynchronous execution
00725  *     } else {
00726  *         ASSERT(returnValue == 1);
00727  *         // handle synchronous completion
00728  *     }
00729  * \endcode
00730  */
00731 static inline int32_t FlashJournal_reset(FlashJournal_t *journal)
00732 {
00733     return journal->ops.reset(journal);
00734 }
00735 
00736 #ifdef __cplusplus
00737 }
00738 #endif // __cplusplus
00739 
00740 #endif /* __FLASH_JOURNAL_H__ */