gpio/gpiolib: Forbid irqchip default trigger if probed over DT

Using a default trigger is a bad idea if using DT to configure
interrupts, as the device's interrupt specifier will always contain
the trigger configuration.

Let's warn about that particular situation, and revert to not
having a default. Hopefully, the couple of drivers still using
this feature will quickly be fixed.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/gpiolib.c

@@ -1613,6 +1613,15 @@ int _gpiochip_irqchip_add(struct gpio_chip *gpiochip,
 	if (gpiochip->of_node)
 		of_node = gpiochip->of_node;
 #endif
+	/*
+	 * Specifying a default trigger is a terrible idea if DT is
+	 * used to configure the interrupts, as you may end-up with
+	 * conflicting triggers. Tell the user, and reset to NONE.
+	 */
+	if (WARN(of_node && type != IRQ_TYPE_NONE,
+		 "%s: Ignoring %d default trigger\n", of_node->full_name, type))
+		type = IRQ_TYPE_NONE;
+
 	gpiochip->irqchip = irqchip;
 	gpiochip->irq_handler = handler;
 	gpiochip->irq_default_type = type;