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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Linus Walleij <linus.walleij@linaro.org>,
        Bartosz Golaszewski <brgl@bgdev.pl>,
        Sasha Levin <alexander.levin@microsoft.com>
Subject: [PATCH 4.15 058/128] gpiolib: dont allow OPEN_DRAIN & OPEN_SOURCE flags simultaneously
Date:   Fri, 16 Mar 2018 16:23:19 +0100
Message-Id: <20180316152339.713629484@linuxfoundation.org>
In-Reply-To: <20180316152336.199007505@linuxfoundation.org>
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4.15-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Bartosz Golaszewski <brgl@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.walleij@linaro.org>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/gpio/gpiolib.c |    9 +++++++++
 1 file changed, 9 insertions(+)

--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -460,6 +460,15 @@ static int linehandle_create(struct gpio
 	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) ||