Re: [PATCH v2 4/4] platform/x86: x86-android-tablets: enable fwnode matching of GPIO chips

[Rafael J. Wysocki]

On Thu, Apr 2, 2026 at 2:54 PM Bartosz Golaszewski
<bartosz.golaszewski@xxxxxxxxxxxxxxxx> wrote:
>
> In order to allow GPIOLIB to match cherryview and baytrail GPIO
> controllers by their firmware nodes instead of their names, we need to
> attach the - currently "dangling" - existing software nodes to their
> target devices dynamically.
>
> We deal with devices described in ACPI so set up a bus notifier waiting
> for the ADD events. We know the name of the device we're waiting for so
> match against it and - on match - assign the appropriate software node
> as the secondary firmware node of the underlying ACPI node. In case the
> event was emitted earlier than this driver's probe: also make sure the
> device was not added before.
>
> Scheduling fine-grained devres actions allows for proper teardown and
> unsetting of the secondary firmware nodes.
>
> Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@xxxxxxxxxxxxxxxx>
> ---
>  drivers/platform/x86/x86-android-tablets/core.c | 127 +++++++++++++++++++++++-
>  1 file changed, 124 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/platform/x86/x86-android-tablets/core.c b/drivers/platform/x86/x86-android-tablets/core.c
> index 021009e9085bec3db9c4daa1f6235600210a6099..9e6e8f272dfe16cda421b569802045c3d94fc0ab 100644
> --- a/drivers/platform/x86/x86-android-tablets/core.c
> +++ b/drivers/platform/x86/x86-android-tablets/core.c
> @@ -13,10 +13,12 @@
>  #include <linux/acpi.h>
>  #include <linux/device.h>
>  #include <linux/dmi.h>
> +#include <linux/fwnode.h>
>  #include <linux/gpio/consumer.h>
>  #include <linux/gpio/machine.h>
>  #include <linux/irq.h>
>  #include <linux/module.h>
> +#include <linux/notifier.h>
>  #include <linux/pci.h>
>  #include <linux/platform_device.h>
>  #include <linux/serdev.h>
> @@ -360,6 +362,124 @@ static const struct software_node *cherryview_gpiochip_node_group[] = {
>         NULL
>  };
>
> +struct auto_secondary_data {
> +       struct notifier_block nb;
> +       struct device *parent;
> +};
> +
> +static void auto_secondary_unset(void *data)
> +{
> +       struct fwnode_handle *fwnode = data;
> +
> +       fwnode->secondary = NULL;
> +}
> +
> +static int acpi_set_secondary_fwnode(struct device *parent, struct device *dev,
> +                                    const struct software_node *const swnode)
> +{
> +       struct acpi_device *device = to_acpi_device(dev);
> +       struct fwnode_handle *fwnode;
> +       int ret;
> +
> +       fwnode = software_node_fwnode(swnode);
> +       if (WARN_ON(!fwnode))
> +               return -ENOENT;
> +
> +       fwnode->secondary = ERR_PTR(-ENODEV);
> +       device->fwnode.secondary = fwnode;
> +
> +       ret = devm_add_action_or_reset(parent, auto_secondary_unset, &device->fwnode);
> +       if (ret)
> +               dev_err(parent, "Failed to schedule the unset action for secondary fwnode\n");
> +
> +       return ret;
> +}
> +
> +static int acpi_auto_secondary_notifier(struct notifier_block *nb,
> +                                       unsigned long action, void *data)
> +{
> +       struct auto_secondary_data *auto_sec = container_of(nb, struct auto_secondary_data, nb);
> +       const struct software_node *const *swnode;
> +       struct device *dev = data;
> +       int ret;
> +
> +       switch (action) {
> +       case BUS_NOTIFY_ADD_DEVICE:
> +               for (swnode = gpiochip_node_group; *swnode; swnode++) {
> +                       if (strcmp((*swnode)->name, dev_name(dev)) == 0) {
> +                               ret = acpi_set_secondary_fwnode(auto_sec->parent, dev, *swnode);
> +                               return ret ? NOTIFY_BAD : NOTIFY_OK;
> +                       }
> +               }
> +               break;
> +       default:
> +               break;
> +       }
> +
> +       return NOTIFY_DONE;
> +}
> +
> +static void auto_secondary_unregister_node_group(void *data)
> +{
> +       const struct software_node **nodes = data;
> +
> +       software_node_unregister_node_group(nodes);
> +}
> +
> +static void auto_secondary_unregister_notifier(void *data)
> +{
> +       struct notifier_block *nb = data;
> +
> +       bus_unregister_notifier(&acpi_bus_type, nb);
> +}

Instead of exporting acpi_bus_type in the previous patch and defining
this function here, can you define

void acpi_bus_unregister_notifier(void *data)
{
       struct notifier_block *nb = data;

       bus_unregister_notifier(&acpi_bus_type, nb);
}

in the previous patch and use it here?

> +
> +static int auto_secondary_fwnode_init(struct device *parent)
> +{
> +       const struct software_node *const *swnode;
> +       struct auto_secondary_data *data;
> +       int ret;
> +
> +       ret = software_node_register_node_group(gpiochip_node_group);
> +       if (ret)
> +               return ret;
> +
> +       ret = devm_add_action_or_reset(parent,
> +                                      auto_secondary_unregister_node_group,
> +                                      gpiochip_node_group);
> +       if (ret)
> +               return ret;
> +
> +       data = devm_kzalloc(parent, sizeof(*data), GFP_KERNEL);
> +       if (!data)
> +               return -ENOMEM;
> +
> +       data->nb.notifier_call = acpi_auto_secondary_notifier;
> +       data->parent = parent;
> +
> +       ret = bus_register_notifier(&acpi_bus_type, &data->nb);
> +       if (ret)
> +               return ret;
> +
> +       ret = devm_add_action_or_reset(parent,
> +                                      auto_secondary_unregister_notifier,
> +                                      &data->nb);
> +       if (ret)
> +               return ret;
> +
> +       /* Device may have been already added. */
> +       for (swnode = gpiochip_node_group; *swnode; swnode++) {
> +               struct device *dev __free(put_device) =
> +                       bus_find_device_by_name(&acpi_bus_type, NULL, (*swnode)->name);
> +               if (dev) {
> +                       ret = acpi_set_secondary_fwnode(parent, dev, *swnode);
> +                       if (ret)
> +                               return ret;
> +               }
> +       }
> +
> +       return 0;
> +}
> +
>  static void x86_android_tablet_remove(struct platform_device *pdev)
>  {
>         int i;
> @@ -391,7 +511,6 @@ static void x86_android_tablet_remove(struct platform_device *pdev)
>
>         software_node_unregister_node_group(gpio_button_swnodes);
>         software_node_unregister_node_group(swnode_group);
> -       software_node_unregister_node_group(gpiochip_node_group);
>  }
>
>  static __init int x86_android_tablet_probe(struct platform_device *pdev)
> @@ -427,9 +546,11 @@ static __init int x86_android_tablet_probe(struct platform_device *pdev)
>                 break;
>         }
>
> -       ret = software_node_register_node_group(gpiochip_node_group);
> -       if (ret)
> +       ret = auto_secondary_fwnode_init(&pdev->dev);
> +       if (ret) {
> +               x86_android_tablet_remove(pdev);
>                 return ret;
> +       }
>
>         ret = software_node_register_node_group(dev_info->swnode_group);
>         if (ret) {
>
> --
> 2.47.3
>