emul: Add sbs_gauge emulator

Add an initial bare-bones functionality sbs_gauge emulator that only
supports register reads tested by the current sbs_gauge driver tests and
what the sbs_driver currently supports.

Signed-off-by: Aaron Massey <aaronmassey@google.com>

subsys/emul/Kconfig

@@ -45,6 +45,12 @@ config EMUL_BMI160
 	  It supports both I2C and SPI which is why it is not in one of the
 	  i2c/ or spi/ directories.
 
+config EMUL_SBS_GAUGE
+	bool "Emulate an SBS 1.1 compliant smart battery fuel gauge"
+	help
+	  It provides readings which follow a simple sequence, thus allowing
+	  test code to check that things are working as expected.
+
 source "subsys/emul/i2c/Kconfig"
 source "subsys/emul/espi/Kconfig"
 

subsys/emul/i2c/CMakeLists.txt

@@ -3,3 +3,6 @@
 # Once we have more than 10 devices we should consider splitting them into
 # subdirectories to match the drivers/ structure.
 zephyr_library_sources_ifdef(CONFIG_EMUL_EEPROM_AT2X	emul_atmel_at24.c)
+
+zephyr_include_directories_ifdef(CONFIG_EMUL_SBS_GAUGE ${ZEPHYR_BASE}/drivers/sensor/sbs_gauge)
+zephyr_library_sources_ifdef(CONFIG_EMUL_SBS_GAUGE		emul_sbs_gauge.c)

subsys/emul/i2c/emul_sbs_gauge.c

@@ -0,0 +1,157 @@
+/*
+ * Copyright 2022 Google LLC
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Emulator for SBS 1.1 compliant smart battery fuel gauge.
+ */
+
+#define DT_DRV_COMPAT sbs_sbs_gauge
+
+#define LOG_LEVEL CONFIG_SENSOR_LOG_LEVEL
+#include <zephyr/logging/log.h>
+LOG_MODULE_REGISTER(sbs_sbs_gauge);
+
+#include <zephyr/device.h>
+#include <zephyr/drivers/emul.h>
+#include <zephyr/drivers/i2c.h>
+#include <zephyr/drivers/i2c_emul.h>
+#include <zephyr/sys/byteorder.h>
+
+#include <sbs_gauge.h>
+
+/** Run-time data used by the emulator */
+struct sbs_gauge_emul_data {
+	/* Stub */
+};
+
+/** Static configuration for the emulator */
+struct sbs_gauge_emul_cfg {
+	/** I2C address of emulator */
+	uint16_t addr;
+};
+
+static void reg_write(const struct emul *target, int reg, int val)
+{
+	ARG_UNUSED(target);
+
+	LOG_INF("write %x = %x", reg, val);
+	switch (reg) {
+	default:
+		LOG_INF("Unknown write %x", reg);
+	}
+}
+
+static int reg_read(const struct emul *target, int reg)
+{
+	int val;
+
+	ARG_UNUSED(target);
+
+	switch (reg) {
+	case SBS_GAUGE_CMD_VOLTAGE:
+	case SBS_GAUGE_CMD_AVG_CURRENT:
+	case SBS_GAUGE_CMD_TEMP:
+	case SBS_GAUGE_CMD_ASOC:
+	case SBS_GAUGE_CMD_FULL_CAPACITY:
+	case SBS_GAUGE_CMD_REM_CAPACITY:
+	case SBS_GAUGE_CMD_NOM_CAPACITY:
+	case SBS_GAUGE_CMD_AVG_TIME2EMPTY:
+	case SBS_GAUGE_CMD_AVG_TIME2FULL:
+	case SBS_GAUGE_CMD_CYCLE_COUNT:
+	case SBS_GAUGE_CMD_DESIGN_VOLTAGE:
+		/* Arbitrary stub value. */
+		val = 1;
+		break;
+	default:
+		LOG_ERR("Unknown register 0x%x read", reg);
+		return -EIO;
+	}
+	LOG_INF("read 0x%x = 0x%x", reg, val);
+
+	return val;
+}
+
+static int sbs_gauge_emul_transfer_i2c(const struct emul *target, struct i2c_msg *msgs,
+				       int num_msgs, int addr)
+{
+	/* Largely copied from emul_bmi160.c */
+	struct sbs_gauge_emul_data *data;
+	unsigned int val;
+	int reg;
+
+	data = target->data;
+
+	__ASSERT_NO_MSG(msgs && num_msgs);
+
+	i2c_dump_msgs("emul", msgs, num_msgs, addr);
+	switch (num_msgs) {
+	case 2:
+		if (msgs->flags & I2C_MSG_READ) {
+			LOG_ERR("Unexpected read");
+			return -EIO;
+		}
+		if (msgs->len != 1) {
+			LOG_ERR("Unexpected msg0 length %d", msgs->len);
+			return -EIO;
+		}
+		reg = msgs->buf[0];
+
+		/* Now process the 'read' part of the message */
+		msgs++;
+		if (msgs->flags & I2C_MSG_READ) {
+			switch (msgs->len - 1) {
+			case 1:
+				val = reg_read(target, reg);
+				msgs->buf[0] = val;
+				break;
+			default:
+				LOG_ERR("Unexpected msg1 length %d", msgs->len);
+				return -EIO;
+			}
+		} else {
+			if (msgs->len != 1) {
+				LOG_ERR("Unexpected msg1 length %d", msgs->len);
+			}
+			reg_write(target, reg, msgs->buf[0]);
+		}
+		break;
+	default:
+		LOG_ERR("Invalid number of messages: %d", num_msgs);
+		return -EIO;
+	}
+
+	return 0;
+}
+
+static const struct i2c_emul_api sbs_gauge_emul_api_i2c = {
+	.transfer = sbs_gauge_emul_transfer_i2c,
+};
+
+/**
+ * Set up a new SBS_GAUGE emulator (I2C)
+ *
+ * @param emul Emulation information
+ * @param parent Device to emulate (must use sbs_gauge driver)
+ * @return 0 indicating success (always)
+ */
+static int emul_sbs_sbs_gauge_init(const struct emul *target, const struct device *parent)
+{
+	ARG_UNUSED(target);
+	ARG_UNUSED(parent);
+
+	return 0;
+}
+
+/*
+ * Main instantiation macro. SBS Gauge Emulator only implemented for I2C
+ */
+#define SBS_GAUGE_EMUL(n)                                                                          \
+	static struct sbs_gauge_emul_data sbs_gauge_emul_data_##n;                                 \
+	static const struct sbs_gauge_emul_cfg sbs_gauge_emul_cfg_##n = {                          \
+		.addr = DT_INST_REG_ADDR(n),                                                       \
+	};                                                                                         \
+	EMUL_DEFINE(emul_sbs_sbs_gauge_init, DT_DRV_INST(n), &sbs_gauge_emul_cfg_##n,              \
+		    &sbs_gauge_emul_data_##n, &sbs_gauge_emul_api_i2c)
+
+DT_INST_FOREACH_STATUS_OKAY(SBS_GAUGE_EMUL)