@@ -1863,6 +1863,13 @@ config GPIO_MPSSE
endmenu
+# This symbol is selected by drivers that need synchronous fake device creation
+config DEV_SYNC_PROBE
+ tristate "Utilities for synchronous fake device creation"
+ help
+ Common helper functions for drivers that need synchronous fake
+ device creation.
+
menu "Virtual GPIO drivers"
config GPIO_AGGREGATOR
@@ -19,6 +19,9 @@ obj-$(CONFIG_GPIO_GENERIC) += gpio-generic.o
# directly supported by gpio-generic
gpio-generic-$(CONFIG_GPIO_GENERIC) += gpio-mmio.o
+# Utilities for drivers that need synchronous fake device creation
+obj-$(CONFIG_DEV_SYNC_PROBE) += dev-sync-probe.o
+
obj-$(CONFIG_GPIO_104_DIO_48E) += gpio-104-dio-48e.o
obj-$(CONFIG_GPIO_104_IDI_48) += gpio-104-idi-48.o
obj-$(CONFIG_GPIO_104_IDIO_16) += gpio-104-idio-16.o
new file mode 100644
@@ -0,0 +1,96 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Common code for drivers creating fake platform devices.
+ *
+ * Provides synchronous device creation: waits for probe completion and
+ * returns the probe success or error status to the device creator.
+ *
+ * Copyright (C) 2025 Bartosz Golaszewski <brgl@bgdev.pl>
+ */
+
+#include <linux/device.h>
+#include <linux/slab.h>
+
+#include "dev-sync-probe.h"
+
+static int dev_sync_probe_notifier_call(struct notifier_block *nb,
+ unsigned long action,
+ void *data)
+{
+ struct dev_sync_probe_data *pdata;
+ struct device *dev = data;
+
+ pdata = container_of(nb, struct dev_sync_probe_data, bus_notifier);
+ if (!device_match_name(dev, pdata->name))
+ return NOTIFY_DONE;
+
+ switch (action) {
+ case BUS_NOTIFY_BOUND_DRIVER:
+ pdata->driver_bound = true;
+ break;
+ case BUS_NOTIFY_DRIVER_NOT_BOUND:
+ pdata->driver_bound = false;
+ break;
+ default:
+ return NOTIFY_DONE;
+ }
+
+ complete(&pdata->probe_completion);
+ return NOTIFY_OK;
+}
+
+void dev_sync_probe_init(struct dev_sync_probe_data *data)
+{
+ memset(data, 0, sizeof(*data));
+ init_completion(&data->probe_completion);
+ data->bus_notifier.notifier_call = dev_sync_probe_notifier_call;
+}
+EXPORT_SYMBOL_GPL(dev_sync_probe_init);
+
+int dev_sync_probe_register(struct dev_sync_probe_data *data,
+ struct platform_device_info *pdevinfo)
+{
+ struct platform_device *pdev;
+ char *name;
+
+ name = kasprintf(GFP_KERNEL, "%s.%u", pdevinfo->name, pdevinfo->id);
+ if (!name)
+ return -ENOMEM;
+
+ data->driver_bound = false;
+ data->name = name;
+ reinit_completion(&data->probe_completion);
+ bus_register_notifier(&platform_bus_type, &data->bus_notifier);
+
+ pdev = platform_device_register_full(pdevinfo);
+ if (IS_ERR(pdev)) {
+ bus_unregister_notifier(&platform_bus_type, &data->bus_notifier);
+ kfree(data->name);
+ return PTR_ERR(pdev);
+ }
+
+ wait_for_completion(&data->probe_completion);
+ bus_unregister_notifier(&platform_bus_type, &data->bus_notifier);
+
+ if (!data->driver_bound) {
+ platform_device_unregister(pdev);
+ kfree(data->name);
+ return -ENXIO;
+ }
+
+ data->pdev = pdev;
+ return 0;
+}
+EXPORT_SYMBOL_GPL(dev_sync_probe_register);
+
+void dev_sync_probe_unregister(struct dev_sync_probe_data *data)
+{
+ platform_device_unregister(data->pdev);
+ kfree(data->name);
+ data->pdev = NULL;
+}
+EXPORT_SYMBOL_GPL(dev_sync_probe_unregister);
+
+MODULE_AUTHOR("Bartosz Golaszewski <brgl@bgdev.pl>");
+MODULE_DESCRIPTION("Utilities for synchronous fake device creation");
+MODULE_LICENSE("GPL");
new file mode 100644
@@ -0,0 +1,25 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef DEV_SYNC_PROBE_H
+#define DEV_SYNC_PROBE_H
+
+#include <linux/completion.h>
+#include <linux/notifier.h>
+#include <linux/platform_device.h>
+
+struct dev_sync_probe_data {
+ struct platform_device *pdev;
+ const char *name;
+
+ /* Synchronize with probe */
+ struct notifier_block bus_notifier;
+ struct completion probe_completion;
+ bool driver_bound;
+};
+
+void dev_sync_probe_init(struct dev_sync_probe_data *data);
+int dev_sync_probe_register(struct dev_sync_probe_data *data,
+ struct platform_device_info *pdevinfo);
+void dev_sync_probe_unregister(struct dev_sync_probe_data *data);
+
+#endif /* DEV_SYNC_PROBE_H */
Both gpio-sim and gpio-virtuser share a mechanism to instantiate a platform device, wait for probe completion, and retrieve the probe success or error status synchronously. With gpio-aggregator planned to adopt this approach for its configfs interface, it's time to factor out the common code. Add dev-sync-probe.[ch] to house helper functions used by all such implementations. No functional change. Signed-off-by: Koichiro Den <koichiro.den@canonical.com> --- drivers/gpio/Kconfig | 7 +++ drivers/gpio/Makefile | 3 ++ drivers/gpio/dev-sync-probe.c | 96 +++++++++++++++++++++++++++++++++++ drivers/gpio/dev-sync-probe.h | 25 +++++++++ 4 files changed, 131 insertions(+) create mode 100644 drivers/gpio/dev-sync-probe.c create mode 100644 drivers/gpio/dev-sync-probe.h