Commit 3444204d authored Dec 07, 2019 by Russell King Committed by Greg Kroah-Hartman Jan 09, 2020

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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent ea0b4277

drivers/gpio/gpiolib.c

+8 −0

Original line number	Original line	Diff line number	Diff line
	@@ -206,6 +206,14 @@ int gpiod_get_direction(struct gpio_desc *desc)
	chip = gpiod_to_chip(desc);		chip = gpiod_to_chip(desc);
	offset = gpio_chip_hwgpio(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)		if (!chip->get_direction)
	return status;		return status;