blob: 4dfbc783290f6b7e0e6e804cff41b832551869fc [file] [log] [blame]
From afaa47dfc89987c171683528f28947df282b2d13 Mon Sep 17 00:00:00 2001
From: Russell King <rmk+kernel@armlinux.org.uk>
Date: Sat, 7 Dec 2019 16:20:18 +0000
Subject: [PATCH] gpiolib: fix up emulated open drain outputs
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@vger.kernel.org>
Suggested-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index e806cd9a14ba..cf55ae4c92f7 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -218,6 +218,14 @@ int gpiod_get_direction(struct gpio_desc *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 -ENOTSUPP;
--
2.7.4