lib: utils/i2c: Add simple FDT based I2C framework

FDT based I2C framework on the top of I2C library.

The drivers are probed on demand by fdt_i2c_adapter_get
function.

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/fdt_i2c.c

@@ -0,0 +1,87 @@
+/*
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright (c) 2021 YADRO
+ *
+ * Authors:
+ *   Nikita Shubin <n.shubin@yadro.com>
+ *
+ * derivate: lib/utils/gpio/fdt_gpio.c
+ * Authors:
+ *   Anup Patel <anup.patel@wdc.com>
+ */
+
+#include <libfdt.h>
+#include <sbi/sbi_error.h>
+#include <sbi_utils/fdt/fdt_helper.h>
+#include <sbi_utils/i2c/fdt_i2c.h>
+
+#include <sbi/sbi_console.h>
+
+static struct fdt_i2c_adapter *i2c_adapter_drivers[] = {
+};
+
+static int fdt_i2c_adapter_init(void *fdt, int nodeoff)
+{
+	int pos, rc;
+	struct fdt_i2c_adapter *drv;
+	const struct fdt_match *match;
+
+	/* Try all I2C drivers one-by-one */
+	for (pos = 0; pos < array_size(i2c_adapter_drivers); pos++) {
+		drv = i2c_adapter_drivers[pos];
+		match = fdt_match_node(fdt, nodeoff, drv->match_table);
+		if (match && drv->init) {
+			rc = drv->init(fdt, nodeoff, match);
+			if (rc == SBI_ENODEV)
+				continue;
+			if (rc)
+				return rc;
+			return 0;
+		}
+	}
+
+	return SBI_ENOSYS;
+}
+
+static int fdt_i2c_adapter_find(void *fdt, int nodeoff,
+				struct i2c_adapter **out_adapter)
+{
+	int rc;
+	struct i2c_adapter *adapter = i2c_adapter_find(nodeoff);
+
+	if (!adapter) {
+		/* I2C adapter not found so initialize matching driver */
+		rc = fdt_i2c_adapter_init(fdt, nodeoff);
+		if (rc)
+			return rc;
+
+		/* Try to find I2C adapter again */
+		adapter = i2c_adapter_find(nodeoff);
+		if (!adapter)
+			return SBI_ENOSYS;
+	}
+
+	if (out_adapter)
+		*out_adapter = adapter;
+
+	return 0;
+}
+
+int fdt_i2c_adapter_get(void *fdt, int nodeoff,
+			struct i2c_adapter **out_adapter)
+{
+	int rc;
+	struct i2c_adapter *adapter;
+
+	if (!fdt || (nodeoff < 0) || !out_adapter)
+		return SBI_EINVAL;
+
+	rc = fdt_i2c_adapter_find(fdt, nodeoff, &adapter);
+	if (rc)
+		return rc;
+
+	*out_adapter = adapter;
+
+	return 0;
+}

lib/utils/i2c/objects.mk

@@ -8,3 +8,4 @@
 #
 
 libsbiutils-objs-y += i2c/i2c.o
+libsbiutils-objs-y += i2c/fdt_i2c.o