i2c: acpi: Introduce i2c_acpi_get_i2c_resource() helper

Besides current two users one more is coming. Definitely makes sense to
introduce a helper.

No functional change intended.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Acked-by: Wolfram Sang <wsa@the-dreams.de>

drivers/i2c/i2c-core-acpi.c

@@ -45,6 +45,33 @@ struct i2c_acpi_lookup {
 	u32 min_speed;
 };
 
+/**
+ * i2c_acpi_get_i2c_resource - Gets I2cSerialBus resource if type matches
+ * @ares:	ACPI resource
+ * @i2c:	Pointer to I2cSerialBus resource will be returned here
+ *
+ * Checks if the given ACPI resource is of type I2cSerialBus.
+ * In this case, returns a pointer to it to the caller.
+ *
+ * Returns true if resource type is of I2cSerialBus, otherwise false.
+ */
+bool i2c_acpi_get_i2c_resource(struct acpi_resource *ares,
+			       struct acpi_resource_i2c_serialbus **i2c)
+{
+	struct acpi_resource_i2c_serialbus *sb;
+
+	if (ares->type != ACPI_RESOURCE_TYPE_SERIAL_BUS)
+		return false;
+
+	sb = &ares->data.i2c_serial_bus;
+	if (sb->type != ACPI_RESOURCE_SERIAL_TYPE_I2C)
+		return false;
+
+	*i2c = sb;
+	return true;
+}
+EXPORT_SYMBOL_GPL(i2c_acpi_get_i2c_resource);
+
 static int i2c_acpi_fill_info(struct acpi_resource *ares, void *data)
 {
 	struct i2c_acpi_lookup *lookup = data;
@@ -52,11 +79,7 @@ static int i2c_acpi_fill_info(struct acpi_resource *ares, void *data)
 	struct acpi_resource_i2c_serialbus *sb;
 	acpi_status status;
 
-	if (info->addr || ares->type != ACPI_RESOURCE_TYPE_SERIAL_BUS)
-		return 1;
-
-	sb = &ares->data.i2c_serial_bus;
-	if (sb->type != ACPI_RESOURCE_SERIAL_TYPE_I2C)
+	if (info->addr || !i2c_acpi_get_i2c_resource(ares, &sb))
 		return 1;
 
 	if (lookup->index != -1 && lookup->n++ != lookup->index)
@@ -534,13 +557,7 @@ i2c_acpi_space_handler(u32 function, acpi_physical_address command,
 		goto err;
 	}
 
-	if (!value64 || ares->type != ACPI_RESOURCE_TYPE_SERIAL_BUS) {
-		ret = AE_BAD_PARAMETER;
-		goto err;
-	}
-
-	sb = &ares->data.i2c_serial_bus;
-	if (sb->type != ACPI_RESOURCE_SERIAL_TYPE_I2C) {
+	if (!value64 || !i2c_acpi_get_i2c_resource(ares, &sb)) {
 		ret = AE_BAD_PARAMETER;
 		goto err;
 	}

include/linux/acpi.h

@@ -1054,6 +1054,17 @@ static inline int acpi_dev_gpio_irq_get(struct acpi_device *adev, int index)
 }
 #endif
 
+#if defined(CONFIG_ACPI) && IS_ENABLED(CONFIG_I2C)
+bool i2c_acpi_get_i2c_resource(struct acpi_resource *ares,
+			       struct acpi_resource_i2c_serialbus **i2c);
+#else
+static inline bool i2c_acpi_get_i2c_resource(struct acpi_resource *ares,
+					     struct acpi_resource_i2c_serialbus **i2c)
+{
+	return false;
+}
+#endif
+
 /* Device properties */
 
 #ifdef CONFIG_ACPI