gpio: Add a method to convert a GPIO to ACPI

When generating ACPI tables we need to convert GPIOs in U-Boot to the ACPI
structures required by ACPI. This is a SoC-specific conversion and cannot
be handled by generic code, so add a new GPIO method to do the conversion.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Wolfgang Wallner <wolfgang.wallner@br-automation.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/drivers/gpio/gpio-uclass.c b/drivers/gpio/gpio-uclass.c
index ab17fa8..9c53299 100644
--- a/drivers/gpio/gpio-uclass.c
+++ b/drivers/gpio/gpio-uclass.c
@@ -13,6 +13,7 @@
 #include <errno.h>
 #include <fdtdec.h>
 #include <malloc.h>
+#include <acpi/acpi_device.h>
 #include <asm/gpio.h>
 #include <dm/device_compat.h>
 #include <linux/bug.h>
@@ -855,6 +856,27 @@
 	return 0;
 }
 
+#if CONFIG_IS_ENABLED(ACPIGEN)
+int gpio_get_acpi(const struct gpio_desc *desc, struct acpi_gpio *gpio)
+{
+	struct dm_gpio_ops *ops;
+
+	memset(gpio, '\0', sizeof(*gpio));
+	if (!dm_gpio_is_valid(desc)) {
+		/* Indicate that the GPIO is not valid */
+		gpio->pin_count = 0;
+		gpio->pins[0] = 0;
+		return -EINVAL;
+	}
+
+	ops = gpio_get_ops(desc->dev);
+	if (!ops->get_acpi)
+		return -ENOSYS;
+
+	return ops->get_acpi(desc, gpio);
+}
+#endif
+
 int gpio_claim_vector(const int *gpio_num_array, const char *fmt)
 {
 	int i, ret;