[PATCH 4.4 20/59] gpiolib: fix up emulated open drain outputs
From: Greg Kroah-Hartman
Date: Sat Jan 11 2020 - 04:54:24 EST
From: Russell King <rmk+kernel@xxxxxxxxxxxxxxx>
commit 256efaea1fdc4e38970489197409a26125ee0aaa upstream.
gpiolib has a corner case with open drain outputs that are emulated.
When such outputs are outputting a logic 1, emulation will set the
hardware to input mode, which will cause gpiod_get_direction() to
report that it is in input mode. This is different from the behaviour
with a true open-drain output.
Unify the semantics here.
Cc: <stable@xxxxxxxxxxxxxxx>
Suggested-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
Signed-off-by: Russell King <rmk+kernel@xxxxxxxxxxxxxxx>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@xxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/gpio/gpiolib.c | 8 ++++++++
1 file changed, 8 insertions(+)
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -163,6 +163,14 @@ int gpiod_get_direction(struct gpio_desc
chip = gpiod_to_chip(desc);
offset = gpio_chip_hwgpio(desc);
+ /*
+ * Open drain emulation using input mode may incorrectly report
+ * input here, fix that up.
+ */
+ if (test_bit(FLAG_OPEN_DRAIN, &desc->flags) &&
+ test_bit(FLAG_IS_OUT, &desc->flags))
+ return 0;
+
if (!chip->get_direction)
return status;