charger: Sample sbs charger driver with tests

Adds a sample sbs charger driver and basics tests.

Signed-off-by: Ricardo Rivera-Matos <rriveram@opensource.cirrus.com>

drivers/charger/emul_sbs_charger.c

@@ -0,0 +1,141 @@
+/*
+ * Copyright 2023 Cirrus Logic, Inc.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * Emulator for SBS 1.1 compliant smart battery charger.
+ */
+
+#define DT_DRV_COMPAT sbs_sbs_charger
+
+#include <zephyr/device.h>
+#include <zephyr/drivers/emul.h>
+#include <zephyr/drivers/i2c.h>
+#include <zephyr/drivers/i2c_emul.h>
+#include <zephyr/logging/log.h>
+#include <zephyr/sys/byteorder.h>
+
+#include "sbs_charger.h"
+
+LOG_MODULE_REGISTER(sbs_sbs_charger);
+
+/** Static configuration for the emulator */
+struct sbs_charger_emul_cfg {
+	/** I2C address of emulator */
+	uint16_t addr;
+};
+
+static int emul_sbs_charger_reg_write(const struct emul *target, int reg, int val)
+{
+	LOG_INF("write %x = %x", reg, val);
+	switch (reg) {
+	default:
+		LOG_ERR("Unknown write %x", reg);
+		return -EIO;
+	}
+
+	return 0;
+}
+
+static int emul_sbs_charger_reg_read(const struct emul *target, int reg, int *val)
+{
+	switch (reg) {
+	case SBS_CHARGER_REG_SPEC_INFO:
+	case SBS_CHARGER_REG_CHARGER_MODE:
+	case SBS_CHARGER_REG_STATUS:
+	case SBS_CHARGER_REG_ALARM_WARNING:
+		/* 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 0;
+}
+
+static int sbs_charger_emul_transfer_i2c(const struct emul *target, struct i2c_msg *msgs,
+					 int num_msgs, int addr)
+{
+	/* Largely copied from emul_sbs_gauge.c */
+	struct sbs_charger_emul_data *data;
+	unsigned int val;
+	int reg;
+	int rc;
+
+	data = target->data;
+
+	i2c_dump_msgs_rw("emul", msgs, num_msgs, addr, false);
+	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:
+				rc = emul_sbs_charger_reg_read(target, reg, &val);
+				if (rc) {
+					/* Return before writing bad value to message buffer */
+					return rc;
+				}
+
+				/* SBS uses SMBus, which sends data in little-endian format. */
+				sys_put_le16(val, msgs->buf);
+				break;
+			default:
+				LOG_ERR("Unexpected msg1 length %d", msgs->len);
+				return -EIO;
+			}
+		} else {
+			/* We write a word (2 bytes by the SBS spec) */
+			if (msgs->len != 2) {
+				LOG_ERR("Unexpected msg1 length %d", msgs->len);
+			}
+			uint16_t value = sys_get_le16(msgs->buf);
+
+			rc = emul_sbs_charger_reg_write(target, reg, value);
+		}
+		break;
+	default:
+		LOG_ERR("Invalid number of messages: %d", num_msgs);
+		return -EIO;
+	}
+
+	return rc;
+}
+
+static const struct i2c_emul_api sbs_charger_emul_api_i2c = {
+	.transfer = sbs_charger_emul_transfer_i2c,
+};
+
+static int emul_sbs_sbs_charger_init(const struct emul *target, const struct device *parent)
+{
+	ARG_UNUSED(target);
+	ARG_UNUSED(parent);
+
+	return 0;
+}
+
+/*
+ * Main instantiation macro. SBS Charger Emulator only implemented for I2C
+ */
+#define SBS_CHARGER_EMUL(n)                                                                        \
+	static const struct sbs_charger_emul_cfg sbs_charger_emul_cfg_##n = {                      \
+		.addr = DT_INST_REG_ADDR(n),                                                       \
+	};                                                                                         \
+	EMUL_DT_INST_DEFINE(n, emul_sbs_sbs_charger_init, NULL, &sbs_charger_emul_cfg_##n,         \
+			    &sbs_charger_emul_api_i2c, NULL)
+
+DT_INST_FOREACH_STATUS_OKAY(SBS_CHARGER_EMUL)