linux-kernel - [PATCH 4.14 42/62] gpiolib: never report open-drain/source lines as input to user-space

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Message-Id: <20190827072703.032244937@linuxfoundation.org>
Date:   Tue, 27 Aug 2019 09:50:47 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Linus Walleij <linus.walleij@...aro.org>
Subject: [PATCH 4.14 42/62] gpiolib: never report open-drain/source lines as input to user-space

From: Bartosz Golaszewski <bgolaszewski@...libre.com>

commit 2c60e6b5c9241b24b8b523fefd3e44fb85622cda upstream.

If the driver doesn't support open-drain/source config options, we
emulate this behavior when setting the direction by calling
gpiod_direction_input() if the default value is 0 (open-source) or
1 (open-drain), thus not actively driving the line in those cases.

This however clears the FLAG_IS_OUT bit for the GPIO line descriptor
and makes the LINEINFO ioctl() incorrectly report this line's mode as
'input' to user-space.

This commit modifies the ioctl() to always set the GPIOLINE_FLAG_IS_OUT
bit in the lineinfo structure's flags field. Since it's impossible to
use the input mode and open-drain/source options at the same time, we
can be sure the reported information will be correct.

Fixes: 521a2ad6f862 ("gpio: add userspace ABI for GPIO line information")
Cc: stable <stable@...r.kernel.org>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@...libre.com>
Link: https://lore.kernel.org/r/20190806114151.17652-1-brgl@bgdev.pl
Signed-off-by: Linus Walleij <linus.walleij@...aro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/gpio/gpiolib.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -971,9 +971,11 @@ static long gpio_ioctl(struct file *filp
 		if (test_bit(FLAG_ACTIVE_LOW, &desc->flags))
 			lineinfo.flags |= GPIOLINE_FLAG_ACTIVE_LOW;
 		if (test_bit(FLAG_OPEN_DRAIN, &desc->flags))
-			lineinfo.flags |= GPIOLINE_FLAG_OPEN_DRAIN;
+			lineinfo.flags |= (GPIOLINE_FLAG_OPEN_DRAIN |
+					   GPIOLINE_FLAG_IS_OUT);
 		if (test_bit(FLAG_OPEN_SOURCE, &desc->flags))
-			lineinfo.flags |= GPIOLINE_FLAG_OPEN_SOURCE;
+			lineinfo.flags |= (GPIOLINE_FLAG_OPEN_SOURCE |
+					   GPIOLINE_FLAG_IS_OUT);
 
 		if (copy_to_user(ip, &lineinfo, sizeof(lineinfo)))
 			return -EFAULT;