[PATCH v2 1/3] serial: mctrl_gpio: Avoid probe failures in case of missing gpiolib

[Schrempf Frieder <frieder.schrempf@kontron.de>]

From: Frieder Schrempf <frieder.schrempf@kontron.de>

If CONFIG_GPIOLIB is not enabled, mctrl_gpio_init() and
mctrl_gpio_init_noauto() will currently return an error pointer with
-ENOSYS. As the mctrl GPIOs are usually optional, drivers need to
check for this condition to allow continue probing.

To avoid the need for this check in each driver, we return NULL
instead, as all the mctrl_gpio_*() functions are skipped anyway.
We also adapt mctrl_gpio_to_gpiod() to be in line with this change.

Signed-off-by: Frieder Schrempf <frieder.schrempf@kontron.de>
Reviewed-by: Fabio Estevam <festevam@gmail.com>
---
Changes in v2
=============
* Move the sh_sci changes to a separate patch
* Add a patch for the 8250 driver
* Add Fabio's R-b tag
---
 drivers/tty/serial/serial_mctrl_gpio.c | 3 +++
 drivers/tty/serial/serial_mctrl_gpio.h | 6 +++---
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/tty/serial/serial_mctrl_gpio.c b/drivers/tty/serial/serial_mctrl_gpio.c
index 2b400189be91..54c43e02e375 100644
--- a/drivers/tty/serial/serial_mctrl_gpio.c
+++ b/drivers/tty/serial/serial_mctrl_gpio.c
@@ -61,6 +61,9 @@ EXPORT_SYMBOL_GPL(mctrl_gpio_set);
 struct gpio_desc *mctrl_gpio_to_gpiod(struct mctrl_gpios *gpios,
 				      enum mctrl_gpio_idx gidx)
 {
+	if (gpios == NULL)
+		return NULL;
+
 	return gpios->gpio[gidx];
 }
 EXPORT_SYMBOL_GPL(mctrl_gpio_to_gpiod);
diff --git a/drivers/tty/serial/serial_mctrl_gpio.h b/drivers/tty/serial/serial_mctrl_gpio.h
index b7d3cca48ede..1b2ff503b2c2 100644
--- a/drivers/tty/serial/serial_mctrl_gpio.h
+++ b/drivers/tty/serial/serial_mctrl_gpio.h
@@ -114,19 +114,19 @@ static inline
 struct gpio_desc *mctrl_gpio_to_gpiod(struct mctrl_gpios *gpios,
 				      enum mctrl_gpio_idx gidx)
 {
-	return ERR_PTR(-ENOSYS);
+	return NULL;
 }
 
 static inline
 struct mctrl_gpios *mctrl_gpio_init(struct uart_port *port, unsigned int idx)
 {
-	return ERR_PTR(-ENOSYS);
+	return NULL;
 }
 
 static inline
 struct mctrl_gpios *mctrl_gpio_init_noauto(struct device *dev, unsigned int idx)
 {
-	return ERR_PTR(-ENOSYS);
+	return NULL;
 }
 
 static inline
-- 
2.17.1

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