[PATCH v3 1/5] pinctrl: renesas: gpio: isolate function gpiochip from parent fwnode

[Dmitry Torokhov <dmitry.torokhov@gmail.com>]

The sh-pfc driver registers two separate gpiochip instances: one for
real GPIOs and another for function GPIOs. Since both share the same
parent platform device, gpiolib's fallback logic causes both chips to
share the same firmware node (fwnode).

This causes ambiguity when using software nodes to describe GPIOs, as
gpiolib may apply hogs meant for one chip to the other if they share the
same node.

Explicitly set gc->fwnode to ERR_PTR(-ENODEV) for the function GPIO
chip. This satisfies gpiolib's check for an existing fwnode and prevents
it from falling back to the parent device's node, while ensuring that no
actual properties or hogs are found on the function chip unless
explicitly assigned later.

Assisted-by: LLM
Acked-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>
Reviewed-by: Linus Walleij <linusw@kernel.org>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
---
 drivers/pinctrl/renesas/gpio.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/pinctrl/renesas/gpio.c b/drivers/pinctrl/renesas/gpio.c
index 2293af642849..4e59dadb7364 100644
--- a/drivers/pinctrl/renesas/gpio.c
+++ b/drivers/pinctrl/renesas/gpio.c
@@ -278,6 +278,12 @@ static int gpio_function_setup(struct sh_pfc_chip *chip)
 
 	gc->request = gpio_function_request;
 
+	/*
+	 * Explicitly mask the parent's fwnode to prevent gpiolib from
+	 * reusing it for function GPIOs.
+	 */
+	gc->fwnode = ERR_PTR(-ENODEV);
+
 	gc->label = pfc->info->name;
 	gc->owner = THIS_MODULE;
 	gc->base = pfc->nr_gpio_pins;

-- 
2.56.0.rc1.315.gc6ed9934b7-goog