[PATCH 5.10.y 2/2] serial: max310x: implement gpio_chip::get_direction()

[Sasha Levin <sashal@kernel.org>]

From: Tapio Reijonen <tapio.reijonen@vaisala.com>

[ Upstream commit a483b1a91b33b7533280e7c3efd2bc1275caef18 ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/tty/serial/max310x.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/tty/serial/max310x.c b/drivers/tty/serial/max310x.c
index 08ea98bd6d5ffc..9cbfaa0c0b051a 100644
--- a/drivers/tty/serial/max310x.c
+++ b/drivers/tty/serial/max310x.c
@@ -1235,6 +1235,17 @@ static void max310x_gpio_set(struct gpio_chip *chip, unsigned int offset, int va
 			    value ? 1 << (offset % 4) : 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);
@@ -1441,6 +1452,7 @@ 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;
-- 
2.53.0