gpiolib: never report open-drain/source lines as 'input' to user-space

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@vger.kernel.org>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Link: https://lore.kernel.org/r/20190806114151.17652-1-brgl@bgdev.pl
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index d367581..3b0d77b 100644 (file)
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -953,9 +953,11 @@ static long gpio_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
                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;