[PATCH AUTOSEL for 4.15 032/102] gpiolib: don't allow OPEN_DRAIN & OPEN_SOURCE flags simultaneously

[Sasha Levin]

From: Bartosz Golaszewski <b...@bgdev.pl>

[ Upstream commit 588fc3bceaf81bbd62e18af6f7bd475e01c2b7e8 ]

Do not allow OPEN_SOURCE & OPEN_DRAIN flags in a single request. If
the hardware actually supports enabling both at the same time the
electrical result would be disastrous.

Suggested-by: Linus Walleij <linus.wall...@linaro.org>
Signed-off-by: Bartosz Golaszewski <b...@bgdev.pl>
Signed-off-by: Linus Walleij <linus.wall...@linaro.org>
Signed-off-by: Sasha Levin <alexander.le...@microsoft.com>
---
 drivers/gpio/gpiolib.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index f6efcf94f6ad..7a5cf5b08c54 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -460,6 +460,15 @@ static int linehandle_create(struct gpio_device *gdev, 
void __user *ip)
        if (lflags & ~GPIOHANDLE_REQUEST_VALID_FLAGS)
                return -EINVAL;
 
+       /*
+        * Do not allow OPEN_SOURCE & OPEN_DRAIN flags in a single request. If
+        * the hardware actually supports enabling both at the same time the
+        * electrical result would be disastrous.
+        */
+       if ((lflags & GPIOHANDLE_REQUEST_OPEN_DRAIN) &&
+           (lflags & GPIOHANDLE_REQUEST_OPEN_SOURCE))
+               return -EINVAL;
+
        /* OPEN_DRAIN and OPEN_SOURCE flags only make sense for output mode. */
        if (!(lflags & GPIOHANDLE_REQUEST_OUTPUT) &&
            ((lflags & GPIOHANDLE_REQUEST_OPEN_DRAIN) ||
-- 
2.14.1