cpu/native: introduce periph_i2c_mock

This allows I2C emulation on native architecture in the same way than
periph_gpio_mock.

All I2C functions from this driver are set as weak to be easily
overridden in each application.

Signed-off-by: Gilles DOFFE <g.doffe@gmail.com>

cpu/native/Makefile.dep

@@ -4,6 +4,9 @@ ifeq ($(OS),Linux)
       USEMODULE += periph_gpio_linux
     endif
   endif
+  ifneq (,$(filter periph_i2c,$(USEMODULE)))
+    USEMODULE += periph_i2c_mock
+  endif
   ifneq (,$(filter periph_spi,$(USEMODULE)))
     USEMODULE += periph_spidev_linux
   endif
@@ -11,6 +14,9 @@ else
   ifneq (,$(filter periph_gpio,$(USEMODULE)))
     USEMODULE += periph_gpio_mock
   endif
+  ifneq (,$(filter periph_i2c,$(USEMODULE)))
+    USEMODULE += periph_i2c_mock
+  endif
 endif
 
 ifneq (,$(filter stdio_default,$(USEMODULE)))

cpu/native/Makefile.features

@@ -14,6 +14,7 @@ FEATURES_PROVIDED += periph_eeprom
 FEATURES_PROVIDED += periph_flashpage
 FEATURES_PROVIDED += periph_flashpage_pagewise
 FEATURES_PROVIDED += periph_hwrng
+FEATURES_PROVIDED += periph_i2c
 FEATURES_PROVIDED += periph_pm
 FEATURES_PROVIDED += periph_pwm
 FEATURES_PROVIDED += periph_timer_periodic

cpu/native/include/periph_conf.h

@@ -71,7 +71,21 @@ extern "C" {
 #  define QDEC_NUMOF (8U)
 #endif
 
-/* MARK: - SPI configuration (Linux host only) */
+/* MARK: - I2C configuration (mock implementation) */
+/**
+ * @name I2C configuration (mock implementation)
+ * @{
+ */
+#if !defined(I2C_NUMOF) || defined(DOXYGEN)
+/**
+ * @brief Amount of I2C devices
+ *
+ * Can be overridden during compile time with `CFLAGS+=-DI2C_NUMOF=n`.
+ */
+#  define I2C_NUMOF   1
+#endif
+/** @} */
+
 /**
  * @name SPI configuration (Linux host only)
  * @{

cpu/native/include/periph_cpu.h

@@ -178,6 +178,27 @@ typedef gpio_mock_t* gpio_t;
 #define PROVIDES_PM_SET_LOWEST
 /** @} */
 
+/**
+ * @name I2C Configuration
+ *
+ * The common I2C implementation is requested to provide the default implementations of the
+ * `i2c_{read,write}_{reg,regs}` functions.
+ */
+
+#define PERIPH_I2C_NEED_READ_REG
+#define PERIPH_I2C_NEED_READ_REGS
+#define PERIPH_I2C_NEED_WRITE_REG
+#define PERIPH_I2C_NEED_WRITE_REGS
+
+#if defined(MODULE_PERIPH_I2C_MOCK) || defined(DOXYGEN)
+/**
+ * @brief   I2C configuration structure type
+ */
+typedef struct {
+    void *dummy;    /**< dummy attribute */
+} i2c_conf_t;
+#endif
+
 /* Configuration for the wrapper around the Linux SPI API (periph_spidev_linux)
  *
  * Needs to go here, otherwise the SPI_NEEDS_ are defined after inclusion of

cpu/native/periph/i2c_mock.c

@@ -0,0 +1,67 @@
+/*
+ * SPDX-FileCopyrightText: 2024 COGIP Robotics Association
+ * SPDX-License-Identifier: LGPL-2.1-only
+ */
+
+/**
+ * @ingroup     cpu_native
+ * @ingroup     drivers_periph_i2c
+ * @{
+ *
+ * @file
+ * @brief       Pluggable no-op I2C implementation
+ *
+ * By default, operations on this bus will always succeed (without actually performing any
+ * action). Reads will produce zeros.
+ *
+ * To provide mocks of a particular connected device, application authors can provide any
+ * of the functions themselves, because all the I2C functions in this implementation are
+ * weak symbols. There is per-bus or per-address dispatch. That means that if multiple
+ * buses or devices are to be mocked with non-zero implementations, the application needs
+ * to provide a single implementation that fans out to the respective mocked device.
+ *
+ * @author      Gilles DOFFE <g.doffe@gmail.com>
+ */
+
+#include <string.h>
+
+#include "periph/i2c.h"
+
+__attribute__((weak)) void i2c_init(i2c_t dev)
+{
+    (void)dev;
+}
+
+__attribute__((weak)) void i2c_acquire(i2c_t dev)
+{
+    (void)dev;
+}
+
+__attribute__((weak)) void i2c_release(i2c_t dev)
+{
+    (void)dev;
+}
+
+__attribute__((weak)) int i2c_read_bytes(i2c_t dev, uint16_t addr,
+                   void *data, size_t len, uint8_t flags)
+{
+    (void)dev;
+    (void)addr;
+    memset(data, 0, len);
+    (void)len;
+    (void)flags;
+
+    return 0;
+}
+
+__attribute__((weak)) int i2c_write_bytes(i2c_t dev, uint16_t addr, const void *data,
+                    size_t len, uint8_t flags)
+{
+    (void)dev;
+    (void)addr;
+    (void)data;
+    (void)len;
+    (void)flags;
+
+    return 0;
+}

makefiles/features_modules.inc.mk

@@ -126,7 +126,7 @@ USEMODULE += $(filter arduino_pwm, $(FEATURES_USED))
 
 # always register a peripheral driver as a required feature when the corresponding
 # module is requested
-PERIPH_IGNORE_MODULES += periph_usbdev_clk periph_gpio_mock periph_gpio_linux periph_spidev_linux
+PERIPH_IGNORE_MODULES += periph_usbdev_clk periph_gpio_mock periph_gpio_linux periph_i2c_mock periph_spidev_linux
 
 ifneq (,$(filter periph_%,$(DEFAULT_MODULE)))
   FEATURES_REQUIRED += $(filter-out $(PERIPH_IGNORE_MODULES),$(filter periph_%,$(USEMODULE)))