[PATCH 4.19 67/98] gpiolib: never report open-drain/source lines as input to user-space

From: Greg Kroah-Hartman
Date: Tue Aug 27 2019 - 03:57:41 EST

From: Bartosz Golaszewski <bgolaszewski@xxxxxxxxxxxx>

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@xxxxxxxxxxxxxxx>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@xxxxxxxxxxxx>
Link: https://lore.kernel.org/r/20190806114151.17652-1-brgl@xxxxxxxx
Signed-off-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

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

--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -1082,9 +1082,11 @@ 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 |
if (test_bit(FLAG_OPEN_SOURCE, &desc->flags))
- lineinfo.flags |= GPIOLINE_FLAG_OPEN_SOURCE;
+ lineinfo.flags |= (GPIOLINE_FLAG_OPEN_SOURCE |

if (copy_to_user(ip, &lineinfo, sizeof(lineinfo)))
return -EFAULT;