serial: max310x: implement gpio_chip::get_direction()

It's strongly recommended for GPIO drivers to always implement the
.get_direction() callback - even when the direction is tracked in
software. The GPIO core emits a warning when the callback is missing
and a user reads the direction of a line, e.g. via
/sys/kernel/debug/gpio.

The MAX310X keeps the GPIO direction in the GPIOCFG register (a set bit
selects output), which the existing direction_input/output callbacks
already program, so the current direction can be read back directly.

Fixes: f65444187a66 ("serial: New serial driver MAX310X")
Cc: stable <stable@kernel.org>
Signed-off-by: Tapio Reijonen <tapio.reijonen@vaisala.com>
Reviewed-by: Linus Walleij <linusw@kernel.org>
Reviewed-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>
Reviewed-by: Hugo Villeneuve <hvilleneuve@dimonoff.com>
Link: https://patch.msgid.link/20260615-b4-serial-max310x-gpio-get-direction-v2-1-4704ba2b181a@vaisala.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/max310x.c b/drivers/tty/serial/max310x.c
index e28e3065c99d3fa9d0520679a1fed8e8ebadb271..92af02a39c7a24f0c59fadbbfb89d5876367709e 100644 (file)
--- a/drivers/tty/serial/max310x.c
+++ b/drivers/tty/serial/max310x.c
@@ -1244,6 +1244,17 @@ static int max310x_gpio_set(struct gpio_chip *chip, unsigned int offset,
        return 0;
 }
 
+static int max310x_gpio_get_direction(struct gpio_chip *chip, unsigned int offset)
+{
+       struct max310x_port *s = gpiochip_get_data(chip);
+       struct uart_port *port = &s->p[offset / 4].port;
+       unsigned int val;
+
+       val = max310x_port_read(port, MAX310X_GPIOCFG_REG);
+
+       return val & BIT(offset % 4) ? GPIO_LINE_DIRECTION_OUT : GPIO_LINE_DIRECTION_IN;
+}
+
 static int max310x_gpio_direction_input(struct gpio_chip *chip, unsigned int offset)
 {
        struct max310x_port *s = gpiochip_get_data(chip);
@@ -1447,6 +1458,7 @@ static int max310x_probe(struct device *dev, const struct max310x_devtype *devty
        s->gpio.owner           = THIS_MODULE;
        s->gpio.parent          = dev;
        s->gpio.label           = devtype->name;
+       s->gpio.get_direction   = max310x_gpio_get_direction;
        s->gpio.direction_input = max310x_gpio_direction_input;
        s->gpio.get             = max310x_gpio_get;
        s->gpio.direction_output= max310x_gpio_direction_output;