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gpiolib: fix up emulated open drain outputs 

commit 256efaea1f 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>
5.4-rM2-2.2.x-imx-squashed
Russell King 2019-12-07 16:20:18 +00:00 committed by Greg Kroah-Hartman
parent 5654d5d25c
commit 530f7c6df9
1 changed files with 8 additions and 0 deletions
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8
drivers/gpio/gpiolib.c
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@ -220,6 +220,14 @@ 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;