serial: mctrl_gpio: enable API usage only for initialized mctrl_gpios struct

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.
Signed-off-by: Yegor Yefremov <yegorslists@googlemail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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]))
@@ -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;