[PATCH] gpiolib: don't clear FLAG_IS_OUT when emulating open-drain/open-source

[Bartosz Golaszewski]

From: Bartosz Golaszewski <bgolaszew...@baylibre.com>

When emulating open-drain/open-source by not actively driving the output
lines - we're simply changing their mode to input. This is wrong as it
will then make it impossible to change the value of such line - it's now
considered to actually be in input mode. If we want to still use the
direction_input() callback for simplicity then we need to set FLAG_IS_OUT
manually in gpiod_direction_output() and not clear it in
gpio_set_open_drain_value_commit() and
gpio_set_open_source_value_commit().

Fixes: c663e5f56737 ("gpio: support native single-ended hardware drivers")
Cc: sta...@vger.kernel.org
Reported-by: Kent Gibson <warthog...@gmail.com>
Signed-off-by: Bartosz Golaszewski <bgolaszew...@baylibre.com>
---
 drivers/gpio/gpiolib.c | 27 +++++++++++++++++++--------
 1 file changed, 19 insertions(+), 8 deletions(-)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index cca749010cd0..6bb4191d3844 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -2769,8 +2769,10 @@ int gpiod_direction_output(struct gpio_desc *desc, int 
value)
                if (!ret)
                        goto set_output_value;
                /* Emulate open drain by not actively driving the line high */
-               if (value)
-                       return gpiod_direction_input(desc);
+               if (value) {
+                       ret = gpiod_direction_input(desc);
+                       goto set_output_flag;
+               }
        }
        else if (test_bit(FLAG_OPEN_SOURCE, &desc->flags)) {
                ret = gpio_set_config(gc, gpio_chip_hwgpio(desc),
@@ -2778,8 +2780,10 @@ int gpiod_direction_output(struct gpio_desc *desc, int 
value)
                if (!ret)
                        goto set_output_value;
                /* Emulate open source by not actively driving the line low */
-               if (!value)
-                       return gpiod_direction_input(desc);
+               if (!value) {
+                       ret = gpiod_direction_input(desc);
+                       goto set_output_flag;
+               }
        } else {
                gpio_set_config(gc, gpio_chip_hwgpio(desc),
                                PIN_CONFIG_DRIVE_PUSH_PULL);
@@ -2787,6 +2791,17 @@ int gpiod_direction_output(struct gpio_desc *desc, int 
value)
 
 set_output_value:
        return gpiod_direction_output_raw_commit(desc, value);
+
+set_output_flag:
+       /*
+        * When emulating open-source or open-drain functionalities by not
+        * actively driving the line (setting mode to input) we still need to
+        * set the IS_OUT flag or otherwise we won't be able to set the line
+        * value anymore.
+        */
+       if (ret == 0)
+               set_bit(FLAG_IS_OUT, &desc->flags);
+       return ret;
 }
 EXPORT_SYMBOL_GPL(gpiod_direction_output);
 
@@ -3147,8 +3162,6 @@ static void gpio_set_open_drain_value_commit(struct 
gpio_desc *desc, bool value)
 
        if (value) {
                err = chip->direction_input(chip, offset);
-               if (!err)
-                       clear_bit(FLAG_IS_OUT, &desc->flags);
        } else {
                err = chip->direction_output(chip, offset, 0);
                if (!err)
@@ -3178,8 +3191,6 @@ static void gpio_set_open_source_value_commit(struct 
gpio_desc *desc, bool value
                        set_bit(FLAG_IS_OUT, &desc->flags);
        } else {
                err = chip->direction_input(chip, offset);
-               if (!err)
-                       clear_bit(FLAG_IS_OUT, &desc->flags);
        }
        trace_gpio_direction(desc_to_gpio(desc), !value, err);
        if (err < 0)
-- 
2.21.0