Re: [PATCH v2 2/4] gpio: swnode: defer probe on references to unregistered software nodes

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

On Thu, Apr 02, 2026 at 02:54:27PM +0200, Bartosz Golaszewski wrote:
> fwnode_property_get_reference_args() now returns -ENXIO when called on a
> software node referencing another software node which has not yet been
> registered as a firmware node. It makes sense to defer probe in this
> situation as the node will most likely be registered later on and we'll
> be able to resolve the reference eventually. Change the behavior of
> swnode_find_gpio() to return -EPROBE_DEFER if the software node reference
> resolution returns -ENXIO.
> 
> Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>
> ---
>  drivers/gpio/gpiolib-swnode.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/drivers/gpio/gpiolib-swnode.c b/drivers/gpio/gpiolib-swnode.c
> index 0d7f3f09a0b4bee0cf1bbdaa8b7b8ae4cd5de581..06d74e9e199de0b91a019e5e15d4b83d330291e7 100644
> --- a/drivers/gpio/gpiolib-swnode.c
> +++ b/drivers/gpio/gpiolib-swnode.c
> @@ -95,6 +95,15 @@ struct gpio_desc *swnode_find_gpio(struct fwnode_handle *fwnode,
>  			break;
>  	}
>  	if (ret) {
> +		if (ret == -ENXIO)


I'll be just sitting here and quoting sashiko all day long ;)

"
If swnode_gpio_get_reference() returns -ENXIO during the first iteration
(for example, when checking the con_id-gpios suffix), won't the loop continue
since the return value is not 0?

Looking at the loop just above this block:

        for_each_gpio_property_name(propname, con_id) {
                ret = swnode_gpio_get_reference(fwnode, propname, idx, &args);
                if (ret == 0)
                        break;
        }

If the initial property check returns -ENXIO, but the subsequent fallback
check for the con_id-gpio suffix returns -ENOENT, the ret variable gets
overwritten. 

When the loop terminates, ret would be -ENOENT instead of -ENXIO. Could this
cause the probe deferral check to evaluate to false and fail the probe
entirely instead of deferring it as intended? 

Should the loop also break early if -ENXIO is encountered?

"

You need to change that to

	if (ret == 0 || ret == -ENXIO)
		break;

because if we get -ENXIO that means the GPIO must be there (the property
exists) but not ready yet and we do not want to fall back to another
suffix. 

Thanks.

-- 
Dmitry