Re: [PATCH] gpio: swnode: restore the swnode-name-against-chip-label matching

[Hans de Goede]

Hi,

On 10-Feb-26 10:48, Bartosz Golaszewski wrote:
> Using the remote firmware node for software node lookup is the right
> thing to do. The GPIO controller we want to resolve should have the
> software node we scooped out of the reference attached to it. However,
> there are existing users who abuse the software node API by creating
> dummy swnodes whose name is set to the expected label string of the GPIO
> controller whose pins they want to control and use them in their local
> swnode references as GPIO properties.
> 
> This used to work when we compared the software node's name to the
> chip's label. When we switched to using a real fwnode lookup, these
> users broke down because the firmware nodes in question were never
> attached to the controllers they were looking for.
> 
> Restore the label matching as a fallback to fix the broken users but add
> a big FIXME urging for a better solution.
> 
> Link: https://lore.kernel.org/all/aYmV5Axyfo76D19T@xxxxxxxxxxxxxxxxxx/
> Cc: stable@xxxxxxxxxxxxxxx # v6.18, v6.19
> Fixes: 216c12047571 ("gpio: swnode: allow referencing GPIO chips by firmware nodes")
> Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxxxxxxxx>
> ---
>  drivers/gpio/gpiolib-swnode.c | 19 +++++++++++++++++++
>  1 file changed, 19 insertions(+)
> 
> diff --git a/drivers/gpio/gpiolib-swnode.c b/drivers/gpio/gpiolib-swnode.c
> index 21478b45c127d..c88313b0026b9 100644
> --- a/drivers/gpio/gpiolib-swnode.c
> +++ b/drivers/gpio/gpiolib-swnode.c
> @@ -42,6 +42,25 @@ static struct gpio_device *swnode_get_gpio_device(struct fwnode_handle *fwnode)
>  
>  fwnode_lookup:
>  	gdev = gpio_device_find_by_fwnode(fwnode);
> +	if (!gdev)

This needs to be:

	if (!gdev && gdev_node->name)


gdev_node->name may be NULL and calling gpio_device_find_by_label()
with a NULL pointer does not end well.

Regards,

Hans




> +		/*
> +		 * FIXME: We shouldn't need to compare the GPIO controller's
> +		 * label against the software node that is supposedly attached
> +		 * to it. However there are currently GPIO users that - knowing
> +		 * the expected label of the GPIO chip whose pins they want to
> +		 * control - set up dummy software nodes named after those GPIO
> +		 * controllers, which aren't actually attached to them. In this
> +		 * case gpio_device_find_by_fwnode() will fail as no device on
> +		 * the GPIO bus is actually associated with the fwnode we're
> +		 * looking for.
> +		 *
> +		 * As a fallback: continue checking the label if we have no
> +		 * match. However, the situation described above is an abuse
> +		 * of the software node API and should be phased out and the
> +		 * following line - eventually removed.
> +		 */
> +		gdev = gpio_device_find_by_label(gdev_node->name);
> +
>  	return gdev ?: ERR_PTR(-EPROBE_DEFER);
>  }
>