Revert "Revert "gpio: Restrict usage of GPIO chip irq members before initialization""

This reverts commit 34c16f1a20.

It is no longer needed as we are able to update the abi at this point in
time.

Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: I2654f99101dc95994cb5cc3328f288401dfe389f

drivers/gpio/gpiolib.c

@@ -1368,6 +1368,16 @@ static int gpiochip_to_irq(struct gpio_chip *gc, unsigned int offset)
 {
 	struct irq_domain *domain = gc->irq.domain;
 
+#ifdef CONFIG_GPIOLIB_IRQCHIP
+	/*
+	 * Avoid race condition with other code, which tries to lookup
+	 * an IRQ before the irqchip has been properly registered,
+	 * i.e. while gpiochip is still being brought up.
+	 */
+	if (!gc->irq.initialized)
+		return -EPROBE_DEFER;
+#endif
+
 	if (!gpiochip_irqchip_irq_valid(gc, offset))
 		return -ENXIO;
 
@@ -1552,6 +1562,15 @@ static int gpiochip_add_irqchip(struct gpio_chip *gc,
 
 	acpi_gpiochip_request_interrupts(gc);
 
+	/*
+	 * Using barrier() here to prevent compiler from reordering
+	 * gc->irq.initialized before initialization of above
+	 * GPIO chip irq members.
+	 */
+	barrier();
+
+	gc->irq.initialized = true;
+
 	return 0;
 }
 

include/linux/gpio/driver.h

@@ -224,6 +224,15 @@ struct gpio_irq_chip {
 				unsigned long *valid_mask,
 				unsigned int ngpios);
 
+	/**
+	 * @initialized:
+	 *
+	 * Flag to track GPIO chip irq member's initialization.
+	 * This flag will make sure GPIO chip irq members are not used
+	 * before they are initialized.
+	 */
+	bool initialized;
+
 	/**
 	 * @valid_mask:
 	 *