POSIX: Add proper I2C driver (via /dev/i2c)

include/arch/posix/driver/i2c.h

+/*
+ * Copyright 2021 Daniel Friesel
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+#ifndef I2C_H
+#define I2C_H
+
+class I2C {
+	private:
+		I2C(const I2C &copy);
+		const char *i2cbus;
+
+	public:
+		I2C (const char *i2cbus) : i2cbus(i2cbus) {}
+		signed char setup();
+		signed char xmit(unsigned char address,
+				unsigned char tx_len, unsigned char *tx_buf,
+				unsigned char rx_len, unsigned char *rx_buf);
+};
+
+extern I2C i2c;
+
+#endif

src/arch/posix/Kconfig

@@ -8,6 +8,10 @@ config arch_posix_driver_counter
 bool "Cycle counter"
 select meta_driver_counter
 
+config arch_posix_driver_i2c
+bool "I2C via /dev/i2c"
+select meta_driver_i2c
+
 config arch_posix_driver_uptime
 bool "Uptime counter"
 select meta_driver_uptime

src/arch/posix/Makefile.inc

@@ -5,6 +5,7 @@
 # SPDX-License-Identifier: BSD-2-Clause
 
 COMMON_FLAGS += -DMULTIPASS_ARCH_posix
+COMMON_FLAGS += -DMULTIPASS_ARCH_HAS_I2C
 
 CC = gcc
 CXX = g++
@@ -27,6 +28,10 @@ ifeq (${timer_s}, 1)
 	CONFIG_arch_posix_driver_uptime = y
 endif
 
+ifdef CONFIG_arch_posix_driver_i2c
+	CXX_TARGETS += src/arch/posix/driver/i2c.cc
+endif
+
 ifdef CONFIG_arch_posix_driver_counter
 	CXX_TARGETS += src/arch/posix/driver/counter.cc
 endif

src/arch/posix/driver/i2c.cc

+/*
+ * Copyright 2021 Daniel Friesel
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+#include "driver/i2c.h"
+#include "arch.h"
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <sys/ioctl.h>
+#include <linux/i2c-dev.h>
+#include <i2c/smbus.h>
+
+
+signed char I2C::setup()
+{
+	return 0;
+}
+
+signed char I2C::xmit(unsigned char address,
+		unsigned char tx_len, unsigned char *tx_buf,
+		unsigned char rx_len, unsigned char *rx_buf)
+{
+	struct i2c_msg messages[2];
+	struct i2c_rdwr_ioctl_data transaction;
+	transaction.nmsgs = 0;
+	transaction.msgs = messages;
+
+	if (tx_len) {
+		messages[transaction.nmsgs].addr = address;
+		messages[transaction.nmsgs].flags = 0;
+		messages[transaction.nmsgs].len = tx_len;
+		messages[transaction.nmsgs].buf = tx_buf;
+		transaction.nmsgs++;
+	}
+	if (rx_len) {
+		messages[transaction.nmsgs].addr = address;
+		messages[transaction.nmsgs].flags = I2C_M_RD;
+		messages[transaction.nmsgs].len = rx_len;
+		messages[transaction.nmsgs].buf = rx_buf;
+		transaction.nmsgs++;
+	}
+
+	int fh = open(i2cbus, O_RDWR);
+
+	if (fh < 0) {
+		return -1;
+	}
+
+	if (ioctl(fh, I2C_RDWR, &transaction) == -1) {
+		return -1;
+	}
+
+	close(fh);
+	return 0;
+}
+
+I2C i2c("/dev/i2c-1");