From: Bartosz Golaszewski Subject: [PATCH] gpiolib: don't allow OPEN_DRAIN & OPEN_SOURCE flags simultaneously Date: Wed, 15 Nov 2017 16:47:43 +0100 Message-ID: <20171115154743.5921-1-brgl@bgdev.pl> Return-path: Received: from mail-wr0-f194.google.com ([209.85.128.194]:53805 "EHLO mail-wr0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932795AbdKOPrt (ORCPT ); Wed, 15 Nov 2017 10:47:49 -0500 Received: by mail-wr0-f194.google.com with SMTP id u40so20812766wrf.10 for ; Wed, 15 Nov 2017 07:47:49 -0800 (PST) Sender: linux-gpio-owner@vger.kernel.org List-Id: linux-gpio@vger.kernel.org To: Linus Walleij Cc: linux-gpio@vger.kernel.org, linux-kernel@vger.kernel.org, Bartosz Golaszewski 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 Signed-off-by: Bartosz Golaszewski --- 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