crc_api.h

00001 /** \addtogroup hal */
00002 /** @{*/
00003 /* mbed Microcontroller Library
00004  * Copyright (c) 2018 ARM Limited
00005  *
00006  * Licensed under the Apache License, Version 2.0 (the "License");
00007  * you may not use this file except in compliance with the License.
00008  * You may obtain a copy of the License at
00009  *
00010  *     http://www.apache.org/licenses/LICENSE-2.0
00011  *
00012  * Unless required by applicable law or agreed to in writing, software
00013  * distributed under the License is distributed on an "AS IS" BASIS,
00014  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
00015  * See the License for the specific language governing permissions and
00016  * limitations under the License.
00017  */
00018 #ifndef MBED_CRC_HAL_API_H
00019 #define MBED_CRC_HAL_API_H
00020 
00021 #include <stdbool.h>
00022 #include <stddef.h>
00023 #include <stdint.h>
00024 
00025 /** CRC Polynomial value
00026  *
00027  * Different polynomial values supported
00028  */
00029 typedef enum crc_polynomial {
00030     POLY_OTHER       = 0,
00031     POLY_8BIT_CCITT  = 0x07,       // x8+x2+x+1
00032     POLY_7BIT_SD     = 0x9,        // x7+x3+1;
00033     POLY_16BIT_CCITT = 0x1021,     // x16+x12+x5+1
00034     POLY_16BIT_IBM   = 0x8005,     // x16+x15+x2+1
00035     POLY_32BIT_ANSI  = 0x04C11DB7, // x32+x26+x23+x22+x16+x12+x11+x10+x8+x7+x5+x4+x2+x+1
00036     POLY_32BIT_REV_ANSI = 0xEDB88320
00037 } crc_polynomial_t;
00038 
00039 typedef struct crc_mbed_config {
00040     /** CRC Polynomial. Example polynomial: 0x21 = 0010_0011 = x^5+x+1 */
00041     uint32_t polynomial;
00042     /** CRC Bit Width */
00043     uint32_t width;
00044     /** Initial seed value for the computation. */
00045     uint32_t initial_xor;
00046     /** Final xor value for the computation. */
00047     uint32_t final_xor;
00048     /** Reflect bits on input. */
00049     bool reflect_in;
00050     /** Reflect bits in final result before returning. */
00051     bool reflect_out;
00052 } crc_mbed_config_t;
00053 
00054 #ifdef DEVICE_CRC
00055 
00056 #ifdef __cplusplus
00057 extern "C" {
00058 #endif
00059 
00060 /**
00061  * \defgroup hal_crc Hardware CRC
00062  *
00063  * The Hardware CRC HAL API provides a low-level interface to the Hardware CRC
00064  * module of a target platform.
00065  *
00066  * # Defined behaviour
00067  *
00068  * * Function hal_crc_is_supported() returns true if platform supports hardware
00069  *   CRC for the given polynomial/width - verified by test ::crc_is_supported_test.
00070  * * Function hal_crc_is_supported() returns false if platform does not support hardware
00071  *   CRC for the given polynomial/width - verified by test ::crc_is_supported_test.
00072  * * Function hal_crc_is_supported() returns false if given pointer to configuration
00073  *   structure is undefined (NULL) - verified by test ::crc_is_supported_invalid_param_test.
00074  * * If CRC module does not support one of the following settings: initial_xor, final_xor
00075  *   reflect_in, reflect_out, then these operations should be handled by the driver
00076  *   - Verified by test ::crc_calc_single_test.
00077  * * Platform which supports hardware CRC must be able to handle at least one of the predefined
00078  *   polynomial/width configurations that can be constructed in the MbedCRC class: POLY_8BIT_CCITT,
00079  *   POLY_7BIT_SD, POLY_16BIT_CCITT, POLY_16BIT_IBM, POLY_32BIT_ANSI
00080  *   - verified by test ::crc_is_supported_test, ::crc_calc_single_test.
00081  * * Function hal_crc_compute_partial_start() configures CRC module with the given configuration
00082  *   - Verified by test ::crc_calc_single_test.
00083  * * Calling hal_crc_compute_partial_start() without finalising the
00084  *   CRC calculation overrides the current configuration - Verified by test ::crc_reconfigure_test.
00085  * * Function hal_crc_compute_partial() writes data to the CRC module - verified by test ::crc_calc_single_test.
00086  * * Function hal_crc_compute_partial() can be call multiple times in succession in order to
00087  *   provide additional data to CRC module - verified by test ::crc_calc_multi_test.
00088  * * Function hal_crc_compute_partial() does nothing if pointer to buffer is undefined or
00089  *   data length is equal to 0 - verified by test ::crc_compute_partial_invalid_param_test.
00090  * * Function hal_crc_get_result() returns the checksum result from the CRC module
00091  *   - verified by tests ::crc_calc_single_test, ::crc_calc_multi_test, ::crc_reconfigure_test.
00092  *
00093  * # Undefined behaviour
00094  *
00095  * * Calling hal_crc_compute_partial_start() function with invalid (unsupported) polynomial.
00096  * * Calling hal_crc_compute_partial() or hal_crc_get_result() functions before hal_crc_compute_partial_start().
00097  * * Calling hal_crc_get_result() function multiple times.
00098  *
00099  * # Non-functional requirements
00100  *
00101  * * CRC configuration provides the following settings:
00102  *   * polynomial - CRC Polynomial,
00103  *   * width - CRC bit width,
00104  *   * initial_xor - seed value for the computation,
00105  *   * final_xor - final xor value for the computation,
00106  *   * reflect_in - reflect bits on input,
00107  *   * reflect_out - reflect bits in final result before returning.
00108  *
00109  * # Potential bugs
00110  *
00111  * @{
00112  */
00113 
00114 /**
00115  * \defgroup hal_crc_tests crc hal tests
00116  * The crc HAL tests ensure driver conformance to defined behaviour.
00117  *
00118  * To run the crc hal tests use the command:
00119  *
00120  *     mbed test -t <toolchain> -m <target> -n tests-mbed_hal-crc*
00121  *
00122  */
00123 
00124 /** Determine if the current platform supports hardware CRC for given polynomial
00125  *
00126  * The purpose of this function is to inform the CRC Platform API whether the
00127  * current platform has a hardware CRC module and that it can support the
00128  * requested polynomial.
00129  *
00130  * Supported polynomials are restricted to the named polynomials that can be
00131  * constructed in the MbedCRC class, POLY_8BIT_CCITT, POLY_7BIT_SD,
00132  * POLY_16BIT_CCITT, POLY_16BIT_IBM and POLY_32BIT_ANSI.
00133  *
00134  * The current platform must support the given polynomials default parameters
00135  * in order to return a true response. These include: reflect in, reflect out,
00136  * initial xor and final xor. For example, POLY_32BIT_ANSI requires an initial
00137  * and final xor of 0xFFFFFFFF, and reflection of both input and output. If any
00138  * of these settings cannot be configured, the polynomial is not supported.
00139  *
00140  * This function is thread safe; it safe to call from multiple contexts if
00141  * required.
00142  *
00143  * \param config Contains CRC configuration parameters for initializing the
00144  *               hardware CRC module. For example, polynomial and initial seed
00145  *               values.
00146  *
00147  * \return  True if running if the polynomial is supported, false if not.
00148  */
00149 bool hal_crc_is_supported(const crc_mbed_config_t *config);
00150 
00151 /** Initialize the hardware CRC module with the given polynomial
00152  *
00153  * After calling this function, the CRC HAL module is ready to receive data
00154  * using the hal_crc_compute_partial() function. The CRC module on the board
00155  * is configured internally with the specified configuration and is ready
00156  * to receive data.
00157  *
00158  * The platform configures itself based on the default configuration
00159  * parameters of the input polynomial.
00160  *
00161  * This function must be called before calling hal_crc_compute_partial().
00162  *
00163  * This function must be called with a valid polynomial supported by the
00164  * platform. The polynomial must be checked for support using the
00165  * hal_crc_is_supported() function.
00166  *
00167  * Calling hal_crc_compute_partial_start() multiple times without finalizing the
00168  * CRC calculation with hal_crc_get_result() overrides the current
00169  * configuration and state, and the intermediate result of the computation is
00170  * lost.
00171  *
00172  * This function is not thread safe. A CRC calculation must not be started from
00173  * two different threads or contexts at the same time; calling this function
00174  * from two different contexts may lead to configurations being overwritten and
00175  * results being lost.
00176  *
00177  * \param config Contains CRC configuration parameters for initializing the
00178  *               hardware CRC module. For example, polynomial and initial seed
00179  *               values.
00180  */
00181 void hal_crc_compute_partial_start(const crc_mbed_config_t *config);
00182 
00183 /** Writes data to the current CRC module.
00184  *
00185  * Writes input data buffer bytes to the CRC data register. The CRC module
00186  * must interpret the data as an array of bytes.
00187  *
00188  * The final transformations are not applied to the data; the CRC module must
00189  * retain the intermediate result so that additional calls to this function
00190  * can be made, appending the additional data to the calculation.
00191  *
00192  * To obtain the final result of the CRC calculation, hal_crc_get_result() is
00193  * called to apply the final transformations to the data.
00194  *
00195  * If the function is passed an undefined pointer, or the size of the buffer is
00196  * specified to be 0, this function does nothing and returns.
00197  *
00198  * This function can be called multiple times in succession. This can be used
00199  * to calculate the CRC result of streamed data.
00200  *
00201  * This function is not thread safe. There is only one instance of the CRC
00202  * module active at a time. Calling this function from multiple contexts
00203  * appends different data to the same, single instance of the module, which causes an
00204  * erroneous value to be calculated.
00205  *
00206  * \param data Input data stream to be written into the CRC calculation
00207  * \param size Size of the data stream in bytes
00208  */
00209 void hal_crc_compute_partial(const uint8_t *data, const size_t size);
00210 
00211 /* Reads the checksum result from the CRC module.
00212  *
00213  * Reads the final checksum result for the final checksum value. The returned
00214  * value is cast as an unsigned 32-bit integer. The actual size of the returned
00215  * result depends on the polynomial used to configure the CRC module.
00216  *
00217  * Additional transformations that are used in the default configuration of the
00218  * input polynomial are applied to the result before it is returned from this
00219  * function. These transformations include: the final xor being appended to the
00220  * calculation, and the result being reflected if required.
00221  *
00222  * Calling this function multiple times is undefined. The first call to this
00223  * function returns the final result of the CRC calculation. The return
00224  * value on successive calls is undefined because the contents of the register after
00225  * accessing them is platform-specific.
00226  *
00227  * This function is not thread safe. There is only one instance of the CRC
00228  * module active at a time. Calling this function from multiple contexts may
00229  * return incorrect data or affect the current state of the module.
00230  *
00231  * \return The final CRC checksum after the reflections and final calculations
00232  *         have been applied.
00233  */
00234 uint32_t hal_crc_get_result(void);
00235 
00236 /**@}*/
00237 
00238 #ifdef __cplusplus
00239 };
00240 #endif
00241 
00242 #endif // DEVICE_CRC
00243 #endif // MBED_CRC_HAL_API_H
00244 
00245 /**@}*/