[PATCH v4 1/9] gpio: mmio: add BGPIOF_NO_INPUT flag for GPO gpiochip

["Clément Le Goffic" <clement.legoffic@foss.st.com>]

When using bgpio_init with a gpiochip acting as a GPO (output only), the
gpiochip ops `direction_input` was set to `bgpio_simple_dir_in` by
default but we have no input ability.

Adding this flag allows to set a valid ops for the `direction_output`
ops without setting a valid ops for `direction_input` by default.

Signed-off-by: Clément Le Goffic <clement.legoffic@foss.st.com>
---
 drivers/gpio/gpio-mmio.c    | 11 ++++++++++-
 include/linux/gpio/driver.h |  1 +
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/gpio/gpio-mmio.c b/drivers/gpio/gpio-mmio.c
index 4841e4ebe7a6..09b9e1275e7e 100644
--- a/drivers/gpio/gpio-mmio.c
+++ b/drivers/gpio/gpio-mmio.c
@@ -335,6 +335,11 @@ static int bgpio_dir_return(struct gpio_chip *gc, unsigned int gpio, bool dir_ou
 		return pinctrl_gpio_direction_input(gc, gpio);
 }
 
+static int bgpio_dir_in_err(struct gpio_chip *gc, unsigned int gpio)
+{
+	return -EINVAL;
+}
+
 static int bgpio_simple_dir_in(struct gpio_chip *gc, unsigned int gpio)
 {
 	return bgpio_dir_return(gc, gpio, false);
@@ -566,7 +571,11 @@ static int bgpio_setup_direction(struct gpio_chip *gc,
 			gc->direction_output = bgpio_dir_out_err;
 		else
 			gc->direction_output = bgpio_simple_dir_out;
-		gc->direction_input = bgpio_simple_dir_in;
+
+		if (flags & BGPIOF_NO_INPUT)
+			gc->direction_input = bgpio_dir_in_err;
+		else
+			gc->direction_input = bgpio_simple_dir_in;
 	}
 
 	return 0;
diff --git a/include/linux/gpio/driver.h b/include/linux/gpio/driver.h
index 4c0294a9104d..42890db9b10e 100644
--- a/include/linux/gpio/driver.h
+++ b/include/linux/gpio/driver.h
@@ -749,6 +749,7 @@ int bgpio_init(struct gpio_chip *gc, struct device *dev,
 #define BGPIOF_NO_OUTPUT		BIT(5) /* only input */
 #define BGPIOF_NO_SET_ON_INPUT		BIT(6)
 #define BGPIOF_PINCTRL_BACKEND		BIT(7) /* Call pinctrl direction setters */
+#define BGPIOF_NO_INPUT			BIT(8) /* only output */
 
 #ifdef CONFIG_GPIOLIB_IRQCHIP
 int gpiochip_irqchip_add_domain(struct gpio_chip *gc,

-- 
2.43.0