/*
 * Copyright (c) 2020 Nordic Semiconductor ASA
 * Copyright 2020 Google LLC
 *
 * SPDX-License-Identifier: Apache-2.0
 */

#ifndef ZEPHYR_INCLUDE_DRIVERS_EMUL_H_
#define ZEPHYR_INCLUDE_DRIVERS_EMUL_H_

/**
 * @brief Emulators used to test drivers and higher-level code that uses them
 * @defgroup io_emulators Emulator interface
 * @ingroup testing
 * @{
 */

#ifdef __cplusplus
extern "C" {
#endif /* __cplusplus */

struct emul;

/* #includes required after forward-declaration of struct emul later defined in this header. */
#include <zephyr/device.h>
#include <zephyr/devicetree.h>
#include <zephyr/drivers/espi_emul.h>
#include <zephyr/drivers/i2c_emul.h>
#include <zephyr/drivers/spi_emul.h>
#include <zephyr/sys/iterable_sections.h>

/**
 * The types of supported buses.
 */
enum emul_bus_type {
	EMUL_BUS_TYPE_I2C,
	EMUL_BUS_TYPE_ESPI,
	EMUL_BUS_TYPE_SPI,
	EMUL_BUS_TYPE_NONE,
};

/**
 * Structure uniquely identifying a device to be emulated
 */
struct emul_link_for_bus {
	const struct device *dev;
};

/** List of emulators attached to a bus */
struct emul_list_for_bus {
	/** Identifiers for children of the node */
	const struct emul_link_for_bus *children;
	/** Number of children of the node */
	unsigned int num_children;
};

/**
 * Standard callback for emulator initialisation providing the initialiser
 * record and the device that calls the emulator functions.
 *
 * @param emul Emulator to init
 * @param parent Parent device that is using the emulator
 */
typedef int (*emul_init_t)(const struct emul *emul, const struct device *parent);

/**
 * Emulator API stub when an emulator is not actually placed on a bus.
 */
struct no_bus_emul {
	void *api;
	uint16_t addr;
};

/** An emulator instance - represents the *target* emulated device/peripheral that is
 * interacted with through an emulated bus. Instances of emulated bus nodes (e.g. i2c_emul)
 * and emulators (i.e. struct emul) are exactly 1..1
 */
struct emul {
	/** function used to initialise the emulator state */
	emul_init_t init;
	/** handle to the device for which this provides low-level emulation */
	const struct device *dev;
	/** Emulator-specific configuration data */
	const void *cfg;
	/** Emulator-specific data */
	void *data;
	/** The bus type that the emulator is attached to */
	enum emul_bus_type bus_type;
	/** Pointer to the emulated bus node */
	union bus {
		struct i2c_emul *i2c;
		struct espi_emul *espi;
		struct spi_emul *spi;
		struct no_bus_emul *none;
	} bus;
	/** Address of the API structure exposed by the emulator instance */
	const void *backend_api;
};

/**
 * @brief Use the devicetree node identifier as a unique name.
 *
 * @param node_id A devicetree node identifier
 */
#define EMUL_DT_NAME_GET(node_id) _CONCAT(__emulreg_, node_id)

/* Get a unique identifier based on the given _dev_node_id's reg property and
 * the bus its on. Intended for use in other internal macros when declaring {bus}_emul
 * structs in peripheral emulators.
 */
#define Z_EMUL_REG_BUS_IDENTIFIER(_dev_node_id) (_CONCAT(_CONCAT(__emulreg_, _dev_node_id), _bus))

/* Conditionally places text based on what bus _dev_node_id is on. */
#define Z_EMUL_BUS(_dev_node_id, _i2c, _espi, _spi, _none)                                         \
	COND_CODE_1(DT_ON_BUS(_dev_node_id, i2c), (_i2c),                                          \
		    (COND_CODE_1(DT_ON_BUS(_dev_node_id, espi), (_espi),                           \
				 (COND_CODE_1(DT_ON_BUS(_dev_node_id, spi), (_spi), (_none))))))
/**
 * @brief Define a new emulator
 *
 * This adds a new struct emul to the linker list of emulations. This is
 * typically used in your emulator's DT_INST_FOREACH_STATUS_OKAY() clause.
 *
 * @param node_id Node ID of the driver to emulate (e.g. DT_DRV_INST(n)); the node_id *MUST* have a
 *        corresponding DEVICE_DT_DEFINE().
 * @param init_fn function to call to initialise the emulator (see emul_init typedef)
 * @param data_ptr emulator-specific data
 * @param cfg_ptr emulator-specific configuration data
 * @param bus_api emulator-specific bus api
 * @param _backend_api emulator-specific backend api
 */
#define EMUL_DT_DEFINE(node_id, init_fn, data_ptr, cfg_ptr, bus_api, _backend_api)                 \
	static struct Z_EMUL_BUS(node_id, i2c_emul, espi_emul, spi_emul, no_bus_emul)              \
		Z_EMUL_REG_BUS_IDENTIFIER(node_id) = {                                             \
			.api = bus_api,                                                            \
			.Z_EMUL_BUS(node_id, addr, chipsel, chipsel, addr) = DT_REG_ADDR(node_id), \
	};                                                                                         \
	const STRUCT_SECTION_ITERABLE(emul, EMUL_DT_NAME_GET(node_id))                             \
	__used = {                                                                                 \
		.init = (init_fn),                                                                 \
		.dev = DEVICE_DT_GET(node_id),                                                     \
		.cfg = (cfg_ptr),                                                                  \
		.data = (data_ptr),                                                                \
		.bus_type = Z_EMUL_BUS(node_id, EMUL_BUS_TYPE_I2C, EMUL_BUS_TYPE_ESPI,             \
				       EMUL_BUS_TYPE_SPI, EMUL_BUS_TYPE_NONE),                     \
		.bus = {.Z_EMUL_BUS(node_id, i2c, espi, spi, none) =                               \
				&(Z_EMUL_REG_BUS_IDENTIFIER(node_id))},                            \
		.backend_api = (_backend_api),                                                     \
	};

/**
 * @brief Like EMUL_DT_DEFINE(), but uses an instance of a DT_DRV_COMPAT compatible instead of a
 *        node identifier.
 *
 * @param inst instance number. The @p node_id argument to EMUL_DT_DEFINE is set to
 *             <tt>DT_DRV_INST(inst)</tt>.
 * @param ... other parameters as expected by EMUL_DT_DEFINE.
 */
#define EMUL_DT_INST_DEFINE(inst, ...) EMUL_DT_DEFINE(DT_DRV_INST(inst), __VA_ARGS__)

/**
 * @brief Get a <tt>const struct emul*</tt> from a devicetree node identifier
 *
 * @details Returns a pointer to an emulator object created from a devicetree
 * node, if any device was allocated by an emulator implementation.
 *
 * If no such device was allocated, this will fail at linker time. If you get an
 * error that looks like <tt>undefined reference to __device_dts_ord_<N></tt>,
 * that is what happened. Check to make sure your emulator implementation is
 * being compiled, usually by enabling the Kconfig options it requires.
 *
 * @param node_id A devicetree node identifier
 * @return A pointer to the emul object created for that node
 */
#define EMUL_DT_GET(node_id) (&EMUL_DT_NAME_GET(node_id))

/**
 * @brief Utility macro to obtain an optional reference to an emulator
 *
 * If the node identifier referes to a node with status `okay`, this returns `EMUL_DT_GET(node_id)`.
 * Otherwise, it returns `NULL`.
 *
 * @param node_id A devicetree node identifier
 * @return a @ref emul reference for the node identifier, which may be `NULL`.
 */
#define EMUL_DT_GET_OR_NULL(node_id)                                                               \
	COND_CODE_1(DT_NODE_HAS_STATUS(node_id, okay), (EMUL_DT_GET(node_id)), (NULL))

/**
 * @brief Set up a list of emulators
 *
 * @param dev Device the emulators are attached to (e.g. an I2C controller)
 * @return 0 if OK
 * @return negative value on error
 */
int emul_init_for_bus(const struct device *dev);

/**
 * @brief Retrieve the emul structure for an emulator by name
 *
 * @details Emulator objects are created via the EMUL_DT_DEFINE() macro and placed in memory by the
 * linker. If the emulator structure is needed for custom API calls, it can be retrieved by the name
 * that the emulator exposes to the system (this is the devicetree node's label by default).
 *
 * @param name Emulator name to search for.  A null pointer, or a pointer to an
 * empty string, will cause NULL to be returned.
 *
 * @return pointer to emulator structure; NULL if not found or cannot be used.
 */
const struct emul *emul_get_binding(const char *name);

/**
 * @}
 */

#define Z_MAYBE_EMUL_DECLARE_INTERNAL(node_id) extern const struct emul EMUL_DT_NAME_GET(node_id);

DT_FOREACH_STATUS_OKAY_NODE(Z_MAYBE_EMUL_DECLARE_INTERNAL);

#ifdef __cplusplus
}
#endif /* __cplusplus */

#endif /* ZEPHYR_INCLUDE_DRIVERS_EMUL_H_ */