gpio: fix "gpio-line-names" property retrieval

Following commit 9427ecbed46cc ("gpio: Rework of_gpiochip_set_names()
to use device property accessors"), "gpio-line-names" DT property is
not retrieved anymore when chip->parent is not set by the driver.
This is due to OF based property reads having been replaced by device
based property reads.

This patch fixes that by making use of
fwnode_property_read_string_array() instead of
device_property_read_string_array() and handing over either
of_fwnode_handle(chip->of_node) or dev_fwnode(chip->parent)
to that function.

Fixes: 9427ecbed46cc ("gpio: Rework of_gpiochip_set_names() to use device property accessors")
Cc: [e-mail]
Signed-off-by: Christophe Leroy <[e-mail]>
Acked-by: Mika Westerberg <[e-mail]>
Signed-off-by: Linus Walleij <[e-mail]>

drivers/gpio/gpiolib-acpi.c

···
 	}
 
 	if (!chip->names)
-		devprop_gpiochip_set_names(chip);
+		devprop_gpiochip_set_names(chip, dev_fwnode(chip->parent));
 
 	acpi_gpiochip_request_regions(acpi_gpio);
 	acpi_gpiochip_scan_gpios(acpi_gpio);

drivers/gpio/gpiolib-devprop.c

···
 /**
  * devprop_gpiochip_set_names - Set GPIO line names using device properties
  * @chip: GPIO chip whose lines should be named, if possible
+ * @fwnode: Property Node containing the gpio-line-names property
  *
  * Looks for device property "gpio-line-names" and if it exists assigns
  * GPIO line names for the chip. The memory allocated for the assigned
  * names belong to the underlying firmware node and should not be released
  * by the caller.
  */
-void devprop_gpiochip_set_names(struct gpio_chip *chip)
+void devprop_gpiochip_set_names(struct gpio_chip *chip,
+				const struct fwnode_handle *fwnode)
 {
 	struct gpio_device *gdev = chip->gpiodev;
 	const char **names;
 	int ret, i;
 
-	if (!chip->parent) {
-		dev_warn(&gdev->dev, "GPIO chip parent is NULL\n");
-		return;
-	}
-
-	ret = device_property_read_string_array(chip->parent, "gpio-line-names",
+	ret = fwnode_property_read_string_array(fwnode, "gpio-line-names",
 						NULL, 0);
 	if (ret < 0)
 		return;
 
 	if (ret != gdev->ngpio) {
-		dev_warn(chip->parent,
+		dev_warn(&gdev->dev,
 			 "names %d do not match number of GPIOs %d\n", ret,
 			 gdev->ngpio);
 		return;
···
 	if (!names)
 		return;
 
-	ret = device_property_read_string_array(chip->parent, "gpio-line-names",
+	ret = fwnode_property_read_string_array(fwnode, "gpio-line-names",
 						names, gdev->ngpio);
 	if (ret < 0) {
-		dev_warn(chip->parent, "failed to read GPIO line names\n");
+		dev_warn(&gdev->dev, "failed to read GPIO line names\n");
 		kfree(names);
 		return;
 	}

drivers/gpio/gpiolib-of.c

···
 
 	/* If the chip defines names itself, these take precedence */
 	if (!chip->names)
-		devprop_gpiochip_set_names(chip);
+		devprop_gpiochip_set_names(chip,
+					   of_fwnode_handle(chip->of_node));
 
 	of_node_get(chip->of_node);
 

drivers/gpio/gpiolib.h

···
 	return desc - &desc->gdev->descs[0];
 }
 
-void devprop_gpiochip_set_names(struct gpio_chip *chip);
+void devprop_gpiochip_set_names(struct gpio_chip *chip,
+				const struct fwnode_handle *fwnode);
 
 /* With descriptor prefix */