[PATCH v4 3/4] serial: mctrl_gpio: enable API usage only for initialized mctrl_gpios struct

[yegorslists@xxxxxxxxxxxxxx]

From: Yegor Yefremov <yegorslists@xxxxxxxxxxxxxx>

This workaround is needed for the cases, where mctrl_gpio API is used
before mctrl_gpio_init() was invoked. This happens in 8250 during
console initialization, as the driver sets DTR signal.

Return NULL in case of initialization errors or absence of GPIOLIB.
This way the above workaround can be safely used.

Signed-off-by: Yegor Yefremov <yegorslists@xxxxxxxxxxxxxx>
---
 drivers/tty/serial/serial_mctrl_gpio.c | 24 +++++++++++++++++++++---
 drivers/tty/serial/serial_mctrl_gpio.h |  2 +-
 2 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/drivers/tty/serial/serial_mctrl_gpio.c b/drivers/tty/serial/serial_mctrl_gpio.c
index a868595..35588c5 100644
--- a/drivers/tty/serial/serial_mctrl_gpio.c
+++ b/drivers/tty/serial/serial_mctrl_gpio.c
@@ -52,6 +52,9 @@ void mctrl_gpio_set(struct mctrl_gpios *gpios, unsigned int mctrl)
 	int value_array[UART_GPIO_MAX];
 	unsigned int count = 0;
 
+	if (gpios == NULL)
+		return;
+
 	for (i = 0; i < UART_GPIO_MAX; i++)
 		if (gpios->gpio[i] && mctrl_gpios_desc[i].dir_out) {
 			desc_array[count] = gpios->gpio[i];
@@ -73,6 +76,9 @@ unsigned int mctrl_gpio_get(struct mctrl_gpios *gpios, unsigned int *mctrl)
 {
 	enum mctrl_gpio_idx i;
 
+	if (gpios == NULL)
+		return *mctrl;
+
 	for (i = 0; i < UART_GPIO_MAX; i++) {
 		if (gpios->gpio[i] && !mctrl_gpios_desc[i].dir_out) {
 			if (gpiod_get_value(gpios->gpio[i]))
@@ -91,6 +97,9 @@ mctrl_gpio_get_outputs(struct mctrl_gpios *gpios, unsigned int *mctrl)
 {
 	enum mctrl_gpio_idx i;
 
+	if (gpios == NULL)
+		return *mctrl;
+
 	for (i = 0; i < UART_GPIO_MAX; i++) {
 		if (gpios->gpio[i] && mctrl_gpios_desc[i].dir_out) {
 			if (gpiod_get_value(gpios->gpio[i]))
@@ -178,7 +187,7 @@ struct mctrl_gpios *mctrl_gpio_init(struct uart_port *port, unsigned int idx)
 
 	gpios = mctrl_gpio_init_noauto(port->dev, idx);
 	if (IS_ERR(gpios))
-		return gpios;
+		return NULL;
 
 	gpios->port = port;
 
@@ -193,7 +202,7 @@ struct mctrl_gpios *mctrl_gpio_init(struct uart_port *port, unsigned int idx)
 			dev_err(port->dev,
 				"failed to find corresponding irq for %s (idx=%d, err=%d)\n",
 				mctrl_gpios_desc[i].name, idx, ret);
-			return ERR_PTR(ret);
+			return NULL;
 		}
 		gpios->irq[i] = ret;
 
@@ -209,7 +218,7 @@ struct mctrl_gpios *mctrl_gpio_init(struct uart_port *port, unsigned int idx)
 			dev_err(port->dev,
 				"failed to request irq for %s (idx=%d, err=%d)\n",
 				mctrl_gpios_desc[i].name, idx, ret);
-			return ERR_PTR(ret);
+			return NULL;
 		}
 	}
 
@@ -221,6 +230,9 @@ void mctrl_gpio_free(struct device *dev, struct mctrl_gpios *gpios)
 {
 	enum mctrl_gpio_idx i;
 
+	if (gpios == NULL)
+		return;
+
 	for (i = 0; i < UART_GPIO_MAX; i++) {
 		if (gpios->irq[i])
 			devm_free_irq(gpios->port->dev, gpios->irq[i], gpios);
@@ -236,6 +248,9 @@ void mctrl_gpio_enable_ms(struct mctrl_gpios *gpios)
 {
 	enum mctrl_gpio_idx i;
 
+	if (gpios == NULL)
+		return;
+
 	/* .enable_ms may be called multiple times */
 	if (gpios->mctrl_on)
 		return;
@@ -258,6 +273,9 @@ void mctrl_gpio_disable_ms(struct mctrl_gpios *gpios)
 {
 	enum mctrl_gpio_idx i;
 
+	if (gpios == NULL)
+		return;
+
 	if (!gpios->mctrl_on)
 		return;
 
diff --git a/drivers/tty/serial/serial_mctrl_gpio.h b/drivers/tty/serial/serial_mctrl_gpio.h
index fa000bc..82c5fbf 100644
--- a/drivers/tty/serial/serial_mctrl_gpio.h
+++ b/drivers/tty/serial/serial_mctrl_gpio.h
@@ -130,7 +130,7 @@ struct gpio_desc *mctrl_gpio_to_gpiod(struct mctrl_gpios *gpios,
 static inline
 struct mctrl_gpios *mctrl_gpio_init(struct uart_port *port, unsigned int idx)
 {
-	return ERR_PTR(-ENOSYS);
+	return NULL;
 }
 
 static inline
-- 
2.1.4

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