lib: utils/i2c: Add generic I2C configuration library

Helper library to keep track of registered I2C adapters,
identified by dts offset, basic send/read functions and
adapter configuration (enable, set dividers, etc...).

Tested-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Reviewed-by: Alexandre Ghiti <alexandre.ghiti@canonical.com>
Tested-by: Alexandre Ghiti <alexandre.ghiti@canonical.com>
Signed-off-by: Nikita Shubin <n.shubin@yadro.com>

lib/utils/i2c/i2c.c

@@ -0,0 +1,75 @@
+/*
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright (c) 2021 YADRO
+ *
+ * Authors:
+ *   Nikita Shubin <n.shubin@yadro.com>
+ *
+ * derivate: lib/utils/gpio/gpio.c
+ * Authors:
+ *   Anup Patel <anup.patel@wdc.com>
+ */
+
+#include <sbi/sbi_error.h>
+#include <sbi_utils/i2c/i2c.h>
+
+static SBI_LIST_HEAD(i2c_adapters_list);
+
+struct i2c_adapter *i2c_adapter_find(int id)
+{
+	struct sbi_dlist *pos;
+
+	sbi_list_for_each(pos, &(i2c_adapters_list)) {
+		struct i2c_adapter *adap = to_i2c_adapter(pos);
+
+		if (adap->id == id)
+			return adap;
+	}
+
+	return NULL;
+}
+
+int i2c_adapter_add(struct i2c_adapter *ia)
+{
+	if (!ia)
+		return SBI_EINVAL;
+
+	if (i2c_adapter_find(ia->id))
+		return SBI_EALREADY;
+
+	sbi_list_add(&(ia->node), &(i2c_adapters_list));
+
+	return 0;
+}
+
+void i2c_adapter_remove(struct i2c_adapter *ia)
+{
+	if (!ia)
+		return;
+
+	sbi_list_del(&(ia->node));
+}
+
+int i2c_adapter_write(struct i2c_adapter *ia, uint8_t addr, uint8_t reg,
+		     uint8_t *buffer, int len)
+{
+	if (!ia)
+		return SBI_EINVAL;
+	if (!ia->write)
+		return SBI_ENOSYS;
+
+	return ia->write(ia, addr, reg, buffer, len);
+}
+
+
+int i2c_adapter_read(struct i2c_adapter *ia, uint8_t addr, uint8_t reg,
+		     uint8_t *buffer, int len)
+{
+	if (!ia)
+		return SBI_EINVAL;
+	if (!ia->read)
+		return SBI_ENOSYS;
+
+	return ia->read(ia, addr, reg, buffer, len);
+}