gpiolib: Override gpiochip numbers with DT aliases

In the same way that other subsystems support the setting of device
id numbers from Device Tree aliases, allow gpiochip numbers to be
derived from "gpiochip<n>" aliases.

Signed-off-by: Phil Elwell <[email protected]>

drivers/gpio/gpiolib.c

@@ -105,6 +105,7 @@ static int gpiochip_irqchip_init_valid_mask(struct gpio_chip *gc);
 static void gpiochip_irqchip_free_valid_mask(struct gpio_chip *gc);
 
 static bool gpiolib_initialized;
+static int first_dynamic_gpiochip_num = -1;
 
 const char *gpiod_get_label(struct gpio_desc *desc)
 {
@@ -927,6 +928,7 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data,
 	unsigned int desc_index;
 	int base = 0;
 	int ret = 0;
+	int id;
 
 	/*
 	 * First: allocate and populate the internal stat container, and
@@ -953,7 +955,16 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data,
 	else if (gc->parent)
 		device_set_node(&gdev->dev, dev_fwnode(gc->parent));
 
-	gdev->id = ida_alloc(&gpio_ida, GFP_KERNEL);
+	if (first_dynamic_gpiochip_num < 0) {
+		id = of_alias_get_highest_id("gpiochip");
+		first_dynamic_gpiochip_num = (id >= 0) ? (id + 1) : 0;
+	}
+
+	id = of_alias_get_id(gdev->dev.of_node, "gpiochip");
+	if (id < 0)
+		id = first_dynamic_gpiochip_num;
+
+	gdev->id = ida_alloc_range(&gpio_ida, id, ~0, GFP_KERNEL);
 	if (gdev->id < 0) {
 		ret = gdev->id;
 		goto err_free_gdev;