spi: Add API to count spi acpi resources

Some ACPI nodes may have more than one Spi Resource.
To be able to handle these case, its necessary to have
a way of counting these resources.

Signed-off-by: Stefan Binding <sbinding@opensource.cirrus.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20220121172431.6876-5-sbinding@opensource.cirrus.com
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi.c

@@ -2324,6 +2324,46 @@ struct acpi_spi_lookup {
 	int			index;
 };
 
+static int acpi_spi_count(struct acpi_resource *ares, void *data)
+{
+	struct acpi_resource_spi_serialbus *sb;
+	int *count = data;
+
+	if (ares->type != ACPI_RESOURCE_TYPE_SERIAL_BUS)
+		return 1;
+
+	sb = &ares->data.spi_serial_bus;
+	if (sb->type != ACPI_RESOURCE_SERIAL_TYPE_SPI)
+		return 1;
+
+	*count = *count + 1;
+
+	return 1;
+}
+
+/**
+ * acpi_spi_count_resources - Count the number of SpiSerialBus resources
+ * @adev:	ACPI device
+ *
+ * Returns the number of SpiSerialBus resources in the ACPI-device's
+ * resource-list; or a negative error code.
+ */
+int acpi_spi_count_resources(struct acpi_device *adev)
+{
+	LIST_HEAD(r);
+	int count = 0;
+	int ret;
+
+	ret = acpi_dev_get_resources(adev, &r, acpi_spi_count, &count);
+	if (ret < 0)
+		return ret;
+
+	acpi_dev_free_resource_list(&r);
+
+	return count;
+}
+EXPORT_SYMBOL_GPL(acpi_spi_count_resources);
+
 static void acpi_spi_parse_apple_properties(struct acpi_device *dev,
 					    struct acpi_spi_lookup *lookup)
 {

include/linux/spi/spi.h

@@ -764,6 +764,7 @@ extern void spi_unregister_controller(struct spi_controller *ctlr);
 extern struct spi_device *acpi_spi_device_alloc(struct spi_controller *ctlr,
 						struct acpi_device *adev,
 						int index);
+int acpi_spi_count_resources(struct acpi_device *adev);
 #endif
 
 /*