[PATCH] gpiolib: don't allow OPEN_DRAIN & OPEN_SOURCE flags simultaneously

From: Bartosz Golaszewski
Date: Wed Nov 15 2017 - 10:47:59 EST


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.walleij@xxxxxxxxxx>
Signed-off-by: Bartosz Golaszewski <brgl@xxxxxxxx>
---
There was a misunderstanding as to what the goal of my previous commit
609aaf6a6029 ("gpiolib: don't allow OPEN_DRAIN & OPEN_SOURCE flags for
input") was, which resulted in discovering another thing that needs
fixing. This change was suggested to me by Linus earlier today.

drivers/gpio/gpiolib.c | 9 +++++++++
1 file changed, 9 insertions(+)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 641a5eb552cb..ec80e0146fd5 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -459,6 +459,15 @@ 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) ||
--
2.13.2