Diff: hal/crc_api.h

Revision:

169:a7c7b631e539

Child:

170:e95d10626187

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/hal/crc_api.h	Fri Jun 22 15:38:59 2018 +0100
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+/** \addtogroup hal */
+/** @{*/
+/* mbed Microcontroller Library
+ * Copyright (c) 2018 ARM Limited
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#ifndef MBED_CRC_HAL_API_H
+#define MBED_CRC_HAL_API_H
+
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+
+/** CRC Polynomial value
+ *
+ * Different polynomial values supported
+ */
+typedef enum crc_polynomial {
+    POLY_OTHER       = 0,
+    POLY_8BIT_CCITT  = 0x07,       // x8+x2+x+1
+    POLY_7BIT_SD     = 0x9,        // x7+x3+1;
+    POLY_16BIT_CCITT = 0x1021,     // x16+x12+x5+1
+    POLY_16BIT_IBM   = 0x8005,     // x16+x15+x2+1
+    POLY_32BIT_ANSI  = 0x04C11DB7, // x32+x26+x23+x22+x16+x12+x11+x10+x8+x7+x5+x4+x2+x+1
+} crc_polynomial_t;
+
+typedef struct crc_mbed_config {
+    /** CRC Polynomial. Example polynomial: 0x21 = 0010_0011 = x^5+x+1 */
+    uint32_t polynomial;
+    /** CRC Bit Width */
+    uint32_t width;
+    /** Initial seed value for the computation. */
+    uint32_t initial_xor;
+    /** Final xor value for the computation. */
+    uint32_t final_xor;
+    /** Reflect bits on input. */
+    bool reflect_in;
+    /** Reflect bits in final result before returning. */
+    bool reflect_out;
+} crc_mbed_config_t;
+
+#ifdef DEVICE_CRC
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * \defgroup hal_crc Hardware CRC
+ *
+ * The Hardware CRC HAL API provides a low-level interface to the Hardware CRC
+ * module of a target platform.
+ *
+ * # Defined behaviour
+ *
+ * * Function hal_crc_is_supported() returns true if platform supports hardware
+ *   CRC for the given polynomial/width - verified by test ::crc_is_supported_test.
+ * * Function hal_crc_is_supported() returns false if platform does not support hardware
+ *   CRC for the given polynomial/width - verified by test ::crc_is_supported_test.
+ * * Function hal_crc_is_supported() returns false if given pointer to configuration
+ *   structure is undefined (NULL) - verified by test ::crc_is_supported_invalid_param_test.
+ * * If CRC module does not support one of the following settings: initial_xor, final_xor
+ *   reflect_in, reflect_out, then these operations should be handled by the driver
+ *   - Verified by test ::crc_calc_single_test.
+ * * Platform which supports hardware CRC must be able to handle at least one of the predefined
+ *   polynomial/width configurations that can be constructed in the MbedCRC class: POLY_8BIT_CCITT,
+ *   POLY_7BIT_SD, POLY_16BIT_CCITT, POLY_16BIT_IBM, POLY_32BIT_ANSI
+ *   - verified by test ::crc_is_supported_test, ::crc_calc_single_test.
+ * * Function hal_crc_compute_partial_start() configures CRC module with the given configuration
+ *   - Verified by test ::crc_calc_single_test.
+ * * Calling hal_crc_compute_partial_start() without finalising the
+ *   CRC calculation overrides the current configuration - Verified by test ::crc_reconfigure_test.
+ * * Function hal_crc_compute_partial() writes data to the CRC module - verified by test ::crc_calc_single_test.
+ * * Function hal_crc_compute_partial() can be call multiple times in succession in order to
+ *   provide additional data to CRC module - verified by test ::crc_calc_multi_test.
+ * * Function hal_crc_compute_partial() does nothing if pointer to buffer is undefined or
+ *   data length is equal to 0 - verified by test ::crc_compute_partial_invalid_param_test.
+ * * Function hal_crc_get_result() returns the checksum result from the CRC module
+ *   - verified by tests ::crc_calc_single_test, ::crc_calc_multi_test, ::crc_reconfigure_test.
+ *
+ * # Undefined behaviour
+ *
+ * * Calling hal_crc_compute_partial_start() function with invalid (unsupported) polynomial.
+ * * Calling hal_crc_compute_partial() or hal_crc_get_result() functions before hal_crc_compute_partial_start().
+ * * Calling hal_crc_get_result() function multiple times.
+ *
+ * # Non-functional requirements
+ *
+ * * CRC configuration provides the following settings:
+ *   * polynomial - CRC Polynomial,
+ *   * width - CRC bit width,
+ *   * initial_xor - seed value for the computation,
+ *   * final_xor - final xor value for the computation,
+ *   * reflect_in - reflect bits on input,
+ *   * reflect_out - reflect bits in final result before returning.
+ *
+ * # Potential bugs
+ *
+ * @{
+ */
+
+/**
+ * \defgroup hal_crc_tests crc hal tests
+ * The crc HAL tests ensure driver conformance to defined behaviour.
+ *
+ * To run the crc hal tests use the command:
+ *
+ *     mbed test -t <toolchain> -m <target> -n tests-mbed_hal-crc*
+ *
+ */
+
+/** Determine if the current platform supports hardware CRC for given polynomial
+ *
+ * The purpose of this function is to inform the CRC Platform API whether the
+ * current platform has a hardware CRC module and that it can support the
+ * requested polynomial.
+ *
+ * Supported polynomials are restricted to the named polynomials that can be
+ * constructed in the MbedCRC class, POLY_8BIT_CCITT, POLY_7BIT_SD,
+ * POLY_16BIT_CCITT, POLY_16BIT_IBM and POLY_32BIT_ANSI.
+ *
+ * The current platform must support the given polynomials default parameters
+ * in order to return a true response. These include: reflect in, reflect out,
+ * initial xor and final xor. For example, POLY_32BIT_ANSI requires an initial
+ * and final xor of 0xFFFFFFFF, and reflection of both input and output. If any
+ * of these settings cannot be configured, the polynomial is not supported.
+ *
+ * This function is thread safe; it safe to call from multiple contexts if
+ * required.
+ *
+ * \param config Contains CRC configuration parameters for initializing the
+ *               hardware CRC module. For example, polynomial and initial seed
+ *               values.
+ *
+ * \return  True if running if the polynomial is supported, false if not.
+ */
+bool hal_crc_is_supported(const crc_mbed_config_t* config);
+
+/** Initialize the hardware CRC module with the given polynomial
+ *
+ * After calling this function, the CRC HAL module is ready to receive data
+ * using the hal_crc_compute_partial() function. The CRC module on the board
+ * is configured internally with the specified configuration and is ready
+ * to receive data.
+ *
+ * The platform configures itself based on the default configuration
+ * parameters of the input polynomial.
+ *
+ * This function must be called before calling hal_crc_compute_partial().
+ *
+ * This function must be called with a valid polynomial supported by the
+ * platform. The polynomial must be checked for support using the
+ * hal_crc_is_supported() function.
+ *
+ * Calling hal_crc_compute_partial_start() multiple times without finalizing the
+ * CRC calculation with hal_crc_get_result() overrides the current
+ * configuration and state, and the intermediate result of the computation is
+ * lost.
+ *
+ * This function is not thread safe. A CRC calculation must not be started from
+ * two different threads or contexts at the same time; calling this function
+ * from two different contexts may lead to configurations being overwritten and
+ * results being lost.
+ *
+ * \param config Contains CRC configuration parameters for initializing the
+ *               hardware CRC module. For example, polynomial and initial seed
+ *               values.
+ */
+void hal_crc_compute_partial_start(const crc_mbed_config_t* config);
+
+/** Writes data to the current CRC module.
+ *
+ * Writes input data buffer bytes to the CRC data register. The CRC module
+ * must interpret the data as an array of bytes.
+ *
+ * The final transformations are not applied to the data; the CRC module must
+ * retain the intermediate result so that additional calls to this function
+ * can be made, appending the additional data to the calculation.
+ *
+ * To obtain the final result of the CRC calculation, hal_crc_get_result() is
+ * called to apply the final transformations to the data.
+ *
+ * If the function is passed an undefined pointer, or the size of the buffer is
+ * specified to be 0, this function does nothing and returns.
+ *
+ * This function can be called multiple times in succession. This can be used
+ * to calculate the CRC result of streamed data.
+ *
+ * This function is not thread safe. There is only one instance of the CRC
+ * module active at a time. Calling this function from multiple contexts
+ * appends different data to the same, single instance of the module, which causes an
+ * erroneous value to be calculated.
+ *
+ * \param data Input data stream to be written into the CRC calculation
+ * \param size Size of the data stream in bytes
+ */
+void hal_crc_compute_partial(const uint8_t *data, const size_t size);
+
+/* Reads the checksum result from the CRC module.
+ *
+ * Reads the final checksum result for the final checksum value. The returned
+ * value is cast as an unsigned 32-bit integer. The actual size of the returned
+ * result depends on the polynomial used to configure the CRC module.
+ *
+ * Additional transformations that are used in the default configuration of the
+ * input polynomial are applied to the result before it is returned from this
+ * function. These transformations include: the final xor being appended to the
+ * calculation, and the result being reflected if required.
+ *
+ * Calling this function multiple times is undefined. The first call to this
+ * function returns the final result of the CRC calculation. The return
+ * value on successive calls is undefined because the contents of the register after
+ * accessing them is platform-specific.
+ *
+ * This function is not thread safe. There is only one instance of the CRC
+ * module active at a time. Calling this function from multiple contexts may
+ * return incorrect data or affect the current state of the module.
+ *
+ * \return The final CRC checksum after the reflections and final calculations
+ *         have been applied.
+ */
+uint32_t hal_crc_get_result(void);
+
+/**@}*/
+
+#ifdef __cplusplus
+};
+#endif
+
+#endif // DEVICE_CRC
+#endif // MBED_CRC_HAL_API_H
+
+/**@}*/