From 72d3200061776264941be1b5a9bb8e926b3b30a5 Mon Sep 17 00:00:00 2001 From: Linus Walleij Date: Thu, 28 Apr 2016 13:33:59 +0200 Subject: [PATCH] gpio: set up initial state from .get_direction() If the gpiochip supports the .get_direction() callback, then the initial state of the descriptor flags should be set up as output accordingly. Also put in comments explaining what is going on. Signed-off-by: Linus Walleij --- drivers/gpio/gpiolib.c | 31 ++++++++++++++++++++++++------- 1 file changed, 24 insertions(+), 7 deletions(-) diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c index bb3195d5e3af..340b021a3782 100644 --- a/drivers/gpio/gpiolib.c +++ b/drivers/gpio/gpiolib.c @@ -565,14 +565,31 @@ int gpiochip_add_data(struct gpio_chip *chip, void *data) struct gpio_desc *desc = &gdev->descs[i]; desc->gdev = gdev; - - /* REVISIT: most hardware initializes GPIOs as inputs (often - * with pullups enabled) so power usage is minimized. Linux - * code should set the gpio direction first thing; but until - * it does, and in case chip->get_direction is not set, we may - * expose the wrong direction in sysfs. + /* + * REVISIT: most hardware initializes GPIOs as inputs + * (often with pullups enabled) so power usage is + * minimized. Linux code should set the gpio direction + * first thing; but until it does, and in case + * chip->get_direction is not set, we may expose the + * wrong direction in sysfs. */ - desc->flags = !chip->direction_input ? (1 << FLAG_IS_OUT) : 0; + + if (chip->get_direction) { + /* + * If we have .get_direction, set up the initial + * direction flag from the hardware. + */ + int dir = chip->get_direction(chip, i); + + if (!dir) + set_bit(FLAG_IS_OUT, &desc->flags); + } else if (!chip->direction_input) { + /* + * If the chip lacks the .direction_input callback + * we logically assume all lines are outputs. + */ + set_bit(FLAG_IS_OUT, &desc->flags); + } } spin_unlock_irqrestore(&gpio_lock, flags);