From 205dc5dbd2b1978f5c75daa0afabf0cf15c8e1fe Mon Sep 17 00:00:00 2001
From: Phil Elwell <phil@raspberrypi.org>
Date: Tue, 24 Apr 2018 14:42:27 +0100
Subject: [PATCH] gpiolib: Don't prevent IRQ usage of output GPIOs

Upstream Linux deems using output GPIOs to generate IRQs as a bogus
use case, even though the BCM2835 GPIO controller is capable of doing
so. A number of users would like to make use of this facility, so
disable the checks.

See: https://github.com/raspberrypi/linux/issues/2527

Signed-off-by: Phil Elwell <phil@raspberrypi.org>
---
 drivers/gpio/gpiolib.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -51,6 +51,8 @@
 #define	extra_checks	0
 #endif
 
+#define dont_test_bit(b,d) (0)
+
 /* Device and char device-related information */
 static DEFINE_IDA(gpio_ida);
 static dev_t gpio_devt;
@@ -2463,8 +2465,8 @@ int gpiod_direction_output(struct gpio_d
 		value = !!value;
 
 	/* GPIOs used for enabled IRQs shall not be set as output */
-	if (test_bit(FLAG_USED_AS_IRQ, &desc->flags) &&
-	    test_bit(FLAG_IRQ_IS_ENABLED, &desc->flags)) {
+	if (dont_test_bit(FLAG_USED_AS_IRQ, &desc->flags) &&
+	    dont_test_bit(FLAG_IRQ_IS_ENABLED, &desc->flags)) {
 		gpiod_err(desc,
 			  "%s: tried to set a GPIO tied to an IRQ as output\n",
 			  __func__);
@@ -3279,8 +3281,8 @@ int gpiochip_lock_as_irq(struct gpio_chi
 	}
 
 	/* To be valid for IRQ the line needs to be input or open drain */
-	if (test_bit(FLAG_IS_OUT, &desc->flags) &&
-	    !test_bit(FLAG_OPEN_DRAIN, &desc->flags)) {
+	if (dont_test_bit(FLAG_IS_OUT, &desc->flags) &&
+	    !dont_test_bit(FLAG_OPEN_DRAIN, &desc->flags)) {
 		chip_err(gc,
 			 "%s: tried to flag a GPIO set as output for IRQ\n",
 			 __func__);
