From 72d3200061776264941be1b5a9bb8e926b3b30a5 Mon Sep 17 00:00:00 2001
From: Linus Walleij <linus.walleij@linaro.org>
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 <linus.walleij@linaro.org>
---
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 bb3195d5e3af0..340b021a37821 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);