[PATCH 5/5] gpiolib: allow pull up/down on outputs

[Kent Gibson <warthog618@xxxxxxxxx>]

This patch allows pull up/down bias to be set on outputs.
Use case is for open source or open drain applications where
internal pull up/down may conflict with external biasing.

Signed-off-by: Kent Gibson <warthog618@xxxxxxxxx>
---
 drivers/gpio/gpiolib.c | 35 +++++++++++++++++++++++------------
 1 file changed, 23 insertions(+), 12 deletions(-)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index f0665ea396cd..38ead7a87d44 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -554,8 +554,9 @@ static int linehandle_create(struct gpio_device *gdev, void __user *ip)
 	     (lflags & GPIOHANDLE_REQUEST_OPEN_SOURCE)))
 		return -EINVAL;
 
-	/* PULL_UP and PULL_DOWN flags only make sense for input mode. */
-	if (!(lflags & GPIOHANDLE_REQUEST_INPUT) &&
+	/* PULL_UP and PULL_DOWN flags only allowed for input or output mode. */
+	if (!((lflags & GPIOHANDLE_REQUEST_INPUT) ||
+	      (lflags & GPIOHANDLE_REQUEST_OUTPUT)) &&
 	    ((lflags & GPIOHANDLE_REQUEST_PULL_UP) ||
 	     (lflags & GPIOHANDLE_REQUEST_PULL_DOWN)))
 		return -EINVAL;
@@ -2932,6 +2933,24 @@ static int gpio_set_config(struct gpio_chip *gc, unsigned offset,
 	return gc->set_config ? gc->set_config(gc, offset, config) : -ENOTSUPP;
 }
 
+static int gpio_set_bias(struct gpio_chip *chip, struct gpio_desc *desc)
+{
+	int bias = 0;
+
+	if (test_bit(FLAG_PULL_UP, &desc->flags) &&
+	    test_bit(FLAG_PULL_DOWN, &desc->flags))
+		bias = PIN_CONFIG_BIAS_DISABLE;
+	else if (test_bit(FLAG_PULL_UP, &desc->flags))
+		bias = PIN_CONFIG_BIAS_PULL_UP;
+	else if (test_bit(FLAG_PULL_DOWN, &desc->flags))
+		bias = PIN_CONFIG_BIAS_PULL_DOWN;
+
+	if (bias)
+		return gpio_set_config(chip, gpio_chip_hwgpio(desc), bias);
+
+	return 0;
+}
+
 /**
  * gpiod_direction_input - set the GPIO direction to input
  * @desc:	GPIO to set to input
@@ -2979,16 +2998,7 @@ int gpiod_direction_input(struct gpio_desc *desc)
 	if (ret == 0)
 		clear_bit(FLAG_IS_OUT, &desc->flags);
 
-	if (test_bit(FLAG_PULL_UP, &desc->flags) &&
-		test_bit(FLAG_PULL_DOWN, &desc->flags))
-		gpio_set_config(chip, gpio_chip_hwgpio(desc),
-				PIN_CONFIG_BIAS_DISABLE);
-	else if (test_bit(FLAG_PULL_UP, &desc->flags))
-		gpio_set_config(chip, gpio_chip_hwgpio(desc),
-				PIN_CONFIG_BIAS_PULL_UP);
-	else if (test_bit(FLAG_PULL_DOWN, &desc->flags))
-		gpio_set_config(chip, gpio_chip_hwgpio(desc),
-				PIN_CONFIG_BIAS_PULL_DOWN);
+	gpio_set_bias(chip, desc);
 
 	trace_gpio_direction(desc_to_gpio(desc), 1, ret);
 
@@ -3114,6 +3124,7 @@ int gpiod_direction_output(struct gpio_desc *desc, int value)
 	}
 
 set_output_value:
+	gpio_set_bias(gc, desc);
 	return gpiod_direction_output_raw_commit(desc, value);
 }
 EXPORT_SYMBOL_GPL(gpiod_direction_output);
-- 
2.23.0